Ants (Hymenoptera: Formicidae) of Christmas Island (Indian ...museum.wa.gov.au/sites/default/files/ANTS... · number of world-wide tramp ants on Christmas Island, this key may also

Records of the Western Australian Museum 25: 45-85 (2008).

Ants (Hymenoptera: Formicidae) of Christmas Island (Indian Ocean):identification and distribution

Volker w. Framenau1,2 and Melissa 1. Thomas2,3,*

1 Department of Terrestrial Zoology, Western Australian Museum, Locked Bag 49,Welshpool DC, Western Australia 6986, Australia.

E-mail: [email protected] School of Animal Biology, University of Western Australia, Crawley,

Western Australia 6009, Australia.3 Parks Australia North, PO Box 867, Christmas Island, Indian Ocean 6798, Australia.

Abstract - The composition of the Christmas Island (Indian Ocean) ant faunais reviewed, leading to the recognition of 52 species in 24 genera and 7subfamilies. This account amalgamates previously published records andrecent extensive surveys of Christmas Island's ant fauna. Eight speciesrepresent new records for Christmas Island: Technomyrmex vitiensis,Camponotus sp. (novaehollandiae group), Cardiocondyla kagutsuchi,Monomorium orientale, M. cf. subcoecum, Tetramorium cf. simillimum, T.smithi and T. walshi. Although some of these new species records representrecent taxonomic advances rather than new introductions, we consider fourspecies to be true new records to Christmas Island. These includeCamponotus sp. (novaehollandiae group), M. orientale, T. smithi and T.walshi. None of the 52 species reported here are considered endemic. Ingeneral, the Christmas Island ant fauna is composed of species that areregarded as worldwide tramps, or that are widespread in the Indo-Australianregion. However, Christmas Island may fall within the native range of someof these species. We provide a key to the ant species of Christmas Island(based on the worker caste), supplemented by comprehensive distributionmaps of these ants on Christmas Island and a short synopsis of each speciesin relation to their ecology and world-wide distribution. Because of the largenumber of world-wide tramp ants on Christmas Island, this key may alsoprove applicable for introduced species resident on other oceanic islands.

INTRODUCTION

The ant fauna of Christmas Island (Indian Ocean)has claimed dubious fame through the impact ofthe introduced Yellow Crazy Ant, Anoplolepisgracilipes (Smith, 1857), on the population of akeystone species, the Red Land Crab, Gecarcoideanatalis (Pocock, 1888). The continuing decline of theRed Land Crab population through directaggression by A. gracilipes workers is changing thecomposition and structure of the rainforest,resulting in major ecosystem disruption andproviding favourable conditions for secondaryinvasions (O'Dowd et a1. 2003). What is less wellknown is that the island harbours a considerablenumber of additional tramp ant species (e.g. Taylor1990), some of which have caused significantecological damage in other regions of theirintroduced ranges (e.g. Holway et a1. 2002; Nessand Bronstein 2004).

*authors in alphabetical order; equal first authorship

Using historical reports, it is difficult to determinehow many species of tramp ants are currentlyestablished on Christmas Island, and what part ofthe fauna can be considered native. Records of theant fauna of Christmas Island have been sporadicand are either published in old or obscure journals(e.g. Crawley 1915; Donisthorpe 1935; Kirby 1888,1900) or listed in unpublished reports that do notnecessarily target ants (e.g. Campbell 1964;Collingwood and Hedlund 1980; Taylor 1990).From the few location records published, it appearsthat these surveys were generally restricted by theirsampling effort and location. The most recent andcomprehensive survey undertaken by CSIRO morethan 15 years ago resulted in a report of 40 antspecies, of which 26 were new records to the islandand 29 were considered tramp species (Taylor1990). However, even this survey did not coverlarge areas of the island such as the north coast fromNorth West Point to Smith Point and large areas ofthe south coast between Egeria point and MiddlePoint (Figure 1). As such, species with localised

46

distribution or a cryptic nature would havecertainly escaped attention. Furthermore, given thedynamic nature of species composition oftransferred ants on oceanic islands (Morrison 1996;Wilson and Taylor 1967), it is highly probable thatadditional species have since establishedthemselves on the island.

This study provides a comprehensive treatmentof the ant fauna of Christmas Island. We combinethe results of rec,ent extensive surveys of ChristmasIsland's ant fauna, with data from historicalrecords to compile an exhaustive species list.Illustrated keys to subfamilies, genera and speciesto all ants of Christmas Island allow accuratespecies identification. In addition, we providedetailed distribution maps of all ants andinformation on their worldwide distribution and,if applicable, their status as tramp species. Bydrawing on ecological information, in combinationwith the distribution of the species in the distinctChristmas Island habitats, we also aim to predictthe possible spread and ecological impact ofintroduced species.

MATERIAL AND METHODS

Christmas IslandChristmas Island lies in the Indian Ocean,

approximately 360 km south of Java and 2600 kmnorth-west of Perth, Australia (Figure 1). Located inthe humid tropics, the island experiences amonsoonal climate with distinct wet (DecemberMay) and dry (June-November) seasons. The islandcovers approximately 135 km2, with a coastlineconsisting predominantly of sheer rocky cliffs from10-20 m high interspersed with a few smallbeaches. The interior is a slightly undulatingplateau, from 160-360 m above sea level andpredominantly covered by tall evergreen closedforest (CIaussen 2005). A series of steep slopes orcliffs with intervening narrow terraces separate thecentral plateau from the shore. Unlike the evergreentall forests of the plateau, many species on theterraces are deciduous, with the canopy usuallybeing closed during the wet season but open tovarying degrees during the dry season. On theterraces the understorey is generally sparser thanthe plateau, with fewer ferns and lilies (Claussen2005).

Although 63% of the island is National Park, todate approximately 25% of the island's rainforesthave been cleared to mine phosphate. Areas thatfall within the current mine lease have variablevegetation cover, ranging in gradient from scorchedearth (recently mined), through weed infestedwasteland, to 40-50 year old native forest regrowthon stockpiles or areas that were cleared but notmined.

V.W. Framenau, M.L. Thomas

Collection MethodsThis study is mainly based on an exhaustive

survey of the ants of Christmas Island in 2005('Island Wide Survey', IWS 2005) and a survey thatpredominantly aimed to document the impact ofthe construction of a large Immigration Receptionand Processing Center (IRPC) (see Figure 1) in theNorthwestern part of the island ('BiodiversityMonitoring Program', BMP). Parks Australia North,Christmas Island (PANCl), undertook bothprograms. Results of these surveys aresupplemented by collections made during cavesurveys (CS) undertaken between 2004 and 2006organised through the Western AustralianSpeleological Group, and opportunistic handcollections by PANCI staff. In addition, we criticallyreviewed published records of Christmas Islandants, since the recent comprehensive collectionsallowed an interpretation of previousmisidentifications.

Island Wide Survey (IWS 2005)The Island Wide Survey (IWS) is undertaken

biennially in the dry months (May-July) as amanagement tool used by Parks Australia North,Christmas Island, to primarily gain information onthe distribution and abundance of the Yellow CrazyAnt and the endemic Red Land Crab. The surveycomprises 980 waypoints in a grid network acrossthe entire island. Each waypoint is separated by atleast 300 m from any other waypoint and has beenaccurately established by computerised GIS ofChristmas Island. In 2005, we incorporated asampling program into the IWS in order to obtain acomprehensive understanding of the common antfauna of the island and its distribution.

A 10 min timed sampling of ants was undertakenat each waypoint. Ants were collected withinapproximately 100 m2 area (50 m x 2 m) at eachwaypoint and searched for on the ground, in leaflitter, under rocks and logs and on tree trunks andlow lying foliage. One person undertook antsampling at each waypoint, but eleven peopleoverall were involved in collecting during thesurvey. These people were trained to have similar.search imagery prior to the commencement of thesurvey. Particular emphasis was placed onobtaining data on species diversity and not speciesabundance; therefore ants that were obviously thesame species (Le. from the same foraging trail) weresub-sampled. Ants were collected using either apaintbrush dipped in alcohol or a pair of softforceps and preserved in EtOB until identified.

Biodiversity Survey (BMP)The biodiversity survey was implemented as part

of the Christmas Island Biodiversity MonitoringProgram (BMP) run by PANCL The survey wasundertaken at three different sites near North West

Ants of Christmas Island 47

SettlementFlying FishCove

mine sites

roads

95' 125 135"

5' 5'

~

15' , 15°

South PointAustralia

4km25' 25'

"1\

95' 105 115' 125' 135 0

North WestPoint

EgeriaPoint

ImmigrationReception andProcessing Centre

Figure 1 Map of Christmas Island illustrating major geographic features and location of mine sites.

Point, separated by at least 400 m. The sitesincluded internal primary forest (a range of tallevergreen rainforest and tall semi-deciduousrainforest) and edge with varying degrees ofdisturbance. At each site, traps were placed at eitherend of two 100 m transects that were spaced 50 mapart (making a total of four trap locations per site).At each trap location two pitfall traps and onecanopy malaise trap, intercept trap and light trapwere placed. Pitfall, malaise and intercept trapswere set for 7 days and nights at each samplingoccasion and light traps were set for one night.Collections were made in January, April, July andOctober during 2004 and 2005. Examining the antscollected from this survey should improve thelikelihood of encountering nocturnal, very smalland cryptic species. l-Iowever, specimens from all

traps were bulk bottled immediately after collectionin each trapping period, so a detailed analysis ofwhich ants were successfully collected with whichtrap was not possible.

Cave Surveys (CS)Ants of a recent survev of selected caves of

Christmas Island were made available through BillHumphreys (Western Australian Museum) and TimMoulds (University of Adelaide). The survey,organised by Darren Brooks through the WesternAustralian Speleological Croup and financed byPANCL was conducted in April/May 2006. Pitfalltraps were the primary method of collection, buthand collections were also made. The \VesternAustralian Museum also holds a small number ofants from a previous cave collection on Christmas

48

Island undertaken in June 2004 (D. Brooksunpublished data). These ants were also madeavailable for shldy by Bill Humphreys.

Species IdentificationSpecies identification was based on available

printed keys, Internet publications or the opinion ofexpert ant taxonomists (see Acknowledgements). Itwas beyond the scope of this study to compare thematerial collected on Christmas Island withrespective type specimens. The knowledge of thetaxonomy and systematics of a large number ofgenera or species groups of ants collected onChristmas Island is rudimentary and requiresextensive revision. Therefore, species identificationmust be taken cautiously and in many cases,definite species names must be considered 'speciesgroups' pending a taxonomic revision of thesegroups. These include Anochetus graeffei,Paratrechina bourbonica, Paratrechina minutula,Ochetellus glaber, Tapinoma minutum and others(see Table 1). Species group designation followsAndersen (2000a, personal communication).Particularly problematic groups include the generaParatrechina and Camponotus. In many cases, wehave consulted ant specialists currently working onspecific taxa (see Acknowledgements) foridentification or confirmation of our identifications.

Generic and species group identificationfollowed Bolton (1994), Shattuck (1999) andAndersen (2000a). Species level identification oftenfollowed Wilson and Taylor (1967), but moredetailed species keys for genera were employed ifavailable. These are listed under the respectivetaxon headings below. Internet identification toolsthat were of particular help were the AustralianAnt Image Database (available at: http://ant.edb.miyakyo-u.ac.jp/AZ/index.html; verified11 October 2007), which contains a number ofimages of ants collected on Christmas Island, andAntWeb (Agosti and Johnson 2005). Some speciespreviously reported from Christmas Island werenot found during the current survey. For thesespecies, we have relied on secondary publicationsfor the compilation of keys.

Voucher specimens of species collected duringthe IWS 2005 are deposited with PANCI and theWestern Australian Museum, Perth. Some antsremain with the consulted specialist: AlanAndersen (CSIRO Darwin, various taxa), BarryBolton (Technomyrmex, Tetramorium), ArchieMacArthur (South Australian Museum,Camponotus), and John LaPolla (SmithsonianInstitute, Washington; Paratrechina). Collections,in particular the reference collection of theWestern Australian Museum, also include a largenumber of sexuals (e.g. queens and males) forfuture systematic study; however, sexuals do notform part of our identification key. Previous


significant collections of ants from ChristmasIsland have been lodged with the AustralianNational Insect Collection (CSIRO, Canberra) (e.g.Taylor 1990).

Subfamilies, genera within subfamilies andspecies within genera are listed alphabetically. Thenomenclature of all species, except Technomyrmexvitiensis, follows Bolton (1995).

AbbreviationsANIC - Australian National Insect Collection,

CSIRO, Canberra; PANCI - Parks Australia North,Christmas Island; WAM - Western AustralianMuseum, Perth.

IWS Island wide survey; BMP - Biodiversitymonitoring program; CS - Cave survey

TL - total length (measured laterally along theextended body of an ant)

RESULTS

General features of the ant fauna of ChristmasIsland

The ant fauna of Christmas Island comprises 52species, representing 24 genera in 7 subfamilies(Table 1). The majority of these species wererecorded during the IWS (39 species; 76%), with theBMP recording 51 '}lo of species (26) and the CS only25% (13). The cave surveys recorded two crypticspecies (Hypoponera punctatissima andPachycondyla (Trachymesopus) darwiniI) that werenot collected during the IWS 2005 or BMP (Table 1).Altogether over 15,000 ants were individuallyidentified and databased during this study.

The richest genera on Christmas Island areTetramorium (8 species), Monomorium (6),Paratrechina (5) and Camponotus (3). The mostcommonly recorded species (those recorded frommore than 200 of the 980 sites) during the IWS 2005were: Paratrechina sp. (bourbonica group) (489waypoints), Anoplolepis gracilipes (478),Tetramorium insolens (462), Pheidole sp. (variabilisgroup) (314), Paratrechina sp. (minutula group)(294), Odontomachlls simi11imus (289), Tapinomamelanocephalllm (279) and Camponotllsmelichloms (268). These eight species represent65'Yo of records from the IWS 2005.

The ants of Christmas Island together occupy allhabitat types on the island. Although most speciesare found predominantly in forested sites, a fewspecies such as Cardiocondyla kaglltsuchi,Paratrechina longicomis, Solenopsis geminata, andTetramorillm bicarinatllm are restricted todisturbed habitats such as mine sites. It appears thatmodification of the environment on ChristmasIsland due to mining activities has producedpatches suitable for these species to becomeestablished.

Ants of Christmas Island

DISCUSSION()f the 52 known ant species on Christmas Island,

eight species represent new records for the island:Tcchnomvrmcx viticnsis, Camponotus sp.(novachollandiac group), Cardiocondvla kagutsuchi, Monomorium oricntalc, lV1. d. suhcoecllm,Tctramoriwn d. simillimum, ·r. smithi, and T.walshi. Some of these new records are based onadvances in taxonomy rather than new species tothe island. These include T. vitiensis, which is hereconsidered a valid species (B. Bolton, personalcommunication) and not a junior synonym of T.alhipes, as apparently reported previously.Monomorium cf. suhcoecum and Cardioconddakagutsuchi are almost certainly the same as M. talpaand C. nuda, respectively (reported in 'faylor 1990,see Heterick 2001; Seifert 2003). Lastly,Telramorium cf. simillimum is extremelv similar toT. simillimum and mav have been included inprevious reports as T. simillimum. Therefore, onlyfour species are here considered as true newrecords for Christmas Island: Camponotlls sp.(novaehollandiae group), M. orientalc, T. smithiand T. walshi.

A recent immigration to Christmas Island issupported for three of these new species by theirdistribution pattern. Monomorium orientalc,Camponotus sp. (l1ovaehollandiae group), and T.smithi are all found at a limited number of sites (I,5, and 11 waypoints respectively) that are groupedclose to the port of entry (Flying Fish Cove). WhileT. 11'illshi was also found at a small number ofwaypoints (four), it is more widely distributedacross the island. However, this species closeassociation with disturbed habitats (such as roadsand minefields) suggests that it may have reachedthis more extensive distribution through humanvectors. Alternatively, given its small size andlimited distribution, T. walshi could have simplybeen overlooked in previous surveys.

We consider nine species that have beenpreviously reported from Christmas Island but notfound during the current surveys to be part of theChristmas Island ant fauna. These include: A.zlvahnvenhurgi, Cerapachys hiroi, P/agiolepisalluaudi, P. exigua, Leptanilla sp., IVlonomoriumdestructor, lvl. pharaonis, Pvramica memhranifera,and Hypoponera opaciceps. Most of these specieswere reported relatively recently by Taylor (1990)and their absence during the recent survevs mostlikely reflects limitations in our collectingtechniques rather than their extinction from theisland. For example, the transect samples of the IWS2005 almost certainly overlooked small and crypticspecies such as ffypoponera punctatissima, H.opaciceps, and Lcptanilla sp. that are known onlyfrom single specimens on Christmas Island (Tavlor1990). While the methodology used during the BMI'survey would be more likely to reveal these species,

49

the small number and location of sites posedlimitations to this survey. Other species notdetected, such as lvl. destructor, show very c!OSl'

association with houses in other parts of theirintroduced ranges (Collingwood et 211. 1997) andmay have also been overlooked using the currentn1l'thodology. In other cases, it is difficult to decidewithout recourse to the original material if amisidentification or sample bias caused the absenceof a species in the current survey. For example, IV1.pharaonis has onlv been reported once(Donisthorpe 1935) and a misidentification ispossible. All other species not listed here, whichhave been previously reported from ChristmasIsland, have been attributed to misidentifications ortaxonomic changes, i.e. they represent juniorsynonyms of other reported species (see Table 1).

In accordance with previous reports of the antfauna from Christmas Island (e.g. Collingwood andHedlund 1980; Taylor 1990), we do not considerany of the species reported here to be endemic. Ingeneral. most species are widespread globally orform part of the Indo-Australian fauna {Table 1).The three species that were originally describedfrom Christmas Island (Camponotus melichlorosKirby, 1888, Leptogenys harmsi (Donisthorpe,1935), and Pachycondyla christmasi (Donisthorpe,1935)) have subsequently been collected in otherparts of the Indo-Pacific region (Taylor 1990). Afurther subspecies initially described fromChristmas Island, Odontomachus hacmatodes var.hreviceps Crawley, 1915, has subsequently beensynonymised with a worldwide tramp, 0.simillimus.

Although it is evident that none of the ants ofChristmas Island are endemic, it is difficult todetermine if the island falls within any of thespecies' native ranges. The first exploration of theisland was undertaken in 1887 (Kirby 1888), a yearbefore human settlement in 1888 (see http://www.deh.gov.au/parks/christmas/islehistory.html;accessed 10 October 2007). During this mission, anda survey undertaken 10 years later, only two antspecies were collected; C. melichloros and L. harmsi(see Table I). Both of these species are widespreadin the Indo-Australian region (Taylor 1990), andChristmas Island mav fall within their nativeranges. Other species, such as 0. simillimus and P.christmasi, could also have a similar status, butwere not reported on Christmas Island until 1915and 1935 respectively. Species reported subsequentto these survevs were most likelv introduced ontotill' island through human comrrlerce. Obviousintroductions include species such as A. gracilipes(but see Wetterer 2005), P. megacephala and S.geminata, all of which are well known invasiveants.

Tlw total number of introduced species onChristmas Island at least equals, if not surpasses the

Table 1 Ant species recorded from Christmas Island. IWS - Island Wide Survey, in brackets the number of waypoints at which each species was found (out of 980); BM!' ~Biodiversity Monitoring Program; CS Cave Surveys 2004/2006. Previous records from Christmas Island: Species name given as in the original publication only if itdeviates from the name given in first column. t indicates a junior synonym of listed species; S indicates a presumed misidentification or putative synonymy (see underrespective species listing in main text). Origin according to Trager (1984)1, Taylor (1990)2, Reimer (1994)', Morrison (1996)4, McGlynn (1999)', Shattuck and Bennett(2001 )6, Holway et a1. (2002)', Seifert (2003) B, ABRS (2006) 9, pers. comm.. B. BoIton* lA (Indo-Australian) = widespread in the Indo-Australian region; T (Tramp)widespread distribution around the globe; I (Invasive) = considered one of the most ecologically damaging introduced ants.

(Jlo

Species

AmblyoponinaeAmblyopone zwaluwenburgi (Williams, 1946)

CerapachyinaeCerapachys biroi Fore!, 1907C. longitarsus (Mayr, 1879)

DolichoderinaeOchetellus sp. (glaber (Mayr, 1862) group)Tapinoma melanocephalum (Fabricius, 1793)Tapinoma sp. (minutum Mayr, 1862 group)Technomyrmex vitiensis Mann, 1921

FormicinaeAnoplolepis gracilipes (Smith, 1857)

Camponotus sp (reticulatus Roger, 1863 group)C. melichloros Kirby, 1888

Camponotus sp. (novaehollandiae Mayr, 1870 group)Paratrechina bourbonica (Fore!, 1886)P. longicomis (Latreille, 1802)Paratrechina sp. (minutula (Forel, 1901) group)Paratrechina sp. (vaga (Forel, 1901) group)P. vividula (Nylander, 1846)Plagiolepis alluaudi Forel, 1894P. exigua Forel, 1894

LeptanillinaeLeptanilla sp.

MyrmicinaeCardiocondyla kagutsuchi Terayama, 1999C. wroughtonii (Fore!, 1890)Monomorium destructor (Jerdon, 1851)

Survey

IWS (1)

IWS (9)IWS (279), BM!', CS

IWS (4)IWS (87), BMI'

IWS (478), BMI', CS

IWS (34), BMI'IWS (268), BMI', CS

IWS (9)IWS (489), BMI', CS

IWS (68), BMI'IWS (294), BMI'

IWS (12)IWS (22)

IWS (23)IWS (31), BMI'

Previous records from Christmas Island

Taylor (1990), known from one queen specimen only

Taylor (1990)Taylor (1990)

Taylor (1990; lridomyrmex glaber (Mayr))Donisthorpe (1935); Taylor (1990); Abbott (2006)Campbell (1964; Tapinoma minutum)Taylor (1990; Technomyrma [sic) albipes (Fr. Smith)t)

Donisthorpe (1935; Anoplolepis longipes Jerd. t); Taylor (1990;Anoplolepis longipes (Jerdon)'); O'Dowd et a1. (2003); Abbott (2005, 20(6)Taylor (1990; Camponotus sp. (widespread Indo-Australian))Kirby (1888, new species); Kirby (1900); Donisthorpe (]935; Camponotus(Tanaemyrmex) melichloros Kirby); Collingwood & Hedlund (1980;Camponotus chloroticus Emery, 18975); Taylor (1990; Camponotus sp.(widespread Indo-Australian)); Abbot (2006; Camponotus maculatus)

Donisthorpe (1935); Taylor (1990)Tweedie (1933); Donisthorpe (1935); Taylor (1990); Abbott (2006)Taylor (1990; Paratrechina minutula (Forel)); Abbott (2006; Paratrechina minutula)Collingwood & Hedlund (1980; Paratrechina vagalCrawley (19]5; Prenolepis vividula Nyl.); Donisthorpe (1935)Collingwood & Hedlund (1980)Collingwood & Hedlund (1980)

Taylor (1990; Leptanilla sp. 1), known from one male specimen only

Taylor (1990; Cardiocondyla nuda (Mayr) S)Taylor (1990)Donisthorpe (1935); Collingwood & Hedlund (1980)

Origin

T

T'lA

T2T 4

lAT*

I

lA'lA'

INT 4

T 4

T'T'T 1

T 4

INT 2,4"

T'

<:~'"!'l

t:l3~

::lr.l

Ps:r;o:3r.lfI>

T >-::len0

"'"T n::r:::.

I ;!;.

lA:3""en-

T'~

""I 7::lCl.

TT

& T

T(1935;

rlA' ,TT

Donisthorpe (1935)Taylor (1990; Monomorillm talpa Emery')Donisthorpe (1935); Collingwood & Hedlund (1980);Collingwood & Hedlund (1980; P. oceanica Mayr, 1866);PheidoJe sp. (widespread Indo-Australian))Taylor (1990; Trichoscapa membranifera (Emery))Crawley (1915; S. geminata F. var. rub Jerd.); Tweedie (1933;geminata rub Jerd.); Donisthorpe (1935; S. gel11inata F. subspeciesrub Jerd.); Collingwood & Hedlund (1980); Taylor (1990)Taylor (1990; Quadristrul11a el11mae (Emery))Taylor (1990)Donisthorpe (1935; Tetral11oriul11 gllineensis F. );Hedlund (1980); Taylor (1990)Taylor (1990)Crawley (1915; Triglvphothrix striatidensTriglyphothrix striatidens Emery); Taylor (1990)Taylor (1990)Donisthorpe (1935); Taylor (1990)

Donisthorpe (1935); Taylor (1990)Bolton (1987); Taylor (1990)

BMI'IWS (1)

IWS (34), BMP

lWS (111), BMI'

IWS (16), BMI'1WS(5)IWS(l)

BMI', CSlWS (37), BMI'

IWS (314), BMI', CS

IWS (462), BMI', CSlWS (128), BMI'

lWS (17), BMI'lWS (163), BMI', CS

IWS(4)lWS(ll)lWS(5)

1846)

1869)18(4)

1890)

T. pacificum Mayr, 1870T. simillimllm (Smith, 1851)T. cf simi!lillm (PF2,2)T. smithi , 11'\79L wa!shi Fore!, 1890

T. inso!ensT. !anuJ4inosum

1851)1872

, 18791'v1. pharaonis (Linnaeus, 1758)tv1. cf. sllbcoecllm Emery, 1894Pheido!e megacepha!a (Fabricius, 1793)Pheido!e sp. (variabilis

S. godeHrovi Mavr 1866It>tralJ1()rillm bicarinatlll11

'r,U+I\'T11P<.:;(H111<..::1 danvinii

'Jl....

lA

lA l, T

L\rrTLA

lAT

lA

lA

(1990; Anochctus graeHei Mayr )Taylor (1990)

(1990), known from one worker onlyTaylor (1990), known from one worker onlyTaylor (1990)Kirby (11'\81'\, 1900; Lobopelta diminllta(1935, new species); Collingwood & Hedlund (191'\0; Leptogenyspequeti [sic] (And '); Taylor (1990)Crawley (1915; Odontomachus haematoda L var. LlTevICtpSnew subspecies'.); Tweedie (1933; Odontomachlls haematodes L ');Donisthorpe (1935; Odontomachlls haematoda L. var. h",,,,i,-,me')·

Campbell (1964); Taylor (1990); Abbott (2006)Donisthorpe (1935; Euponera (!'v1esoponera) christmasi, new species);Collingwood & Hedlund (1980; Pachvcondyla solitaria Mayr'); Taylor (1990;Brachyponera christmasi (Donisthorpe)); Abbott (2006; Brachyponera christnu.,,1Taylor (1990) (Trachymesopus considered junior synonym of l'"dll',·nn,fFi.,

in Bolton 1995)Taylor (1990; Platvthyrea wroughtonii Forel')Taylor (1990)

IWS (17), BMI'lWS (14), BMI'

CSIWS(6)

lWS (68), BMI'

IWS (289), BMI'

lWS (25), CSlWS (2), BMI', CS

lWS (192), BMI', CS

1893) CS

11'\59)

christmasi

1870 group)11'\(0)

PonerinaeAnochetlls sp.

(,n'tlnnn/)r,l c()[1{;nis'

181'\7)1859

861

Odontomachus simillimlls Smith, 11'\51'\


2. Petiole with distinct rear face (Figures 2A, D)or reduced (Figure 2C) 3

Petiole with distinct front and top faces, but noseparate rear face as the rear face is attached

28

postpetiolepetiole

publication of this key may not key out correctly ormay not key out at all.

For a detailed description of ant morphology andterminology, the reader is referred to Holldoblerand Wilson (1990), Bolton (1994) and Shattuck(1999), although key characters are illustrated formost couplets.

Ants should be examined dry (preferably pinnedfor easier handling), as only dry specimens allowthe accurate examination of cuticular patterns andsetae arrangement that are generally important forspecies identification. Some identification coupletsrequire measurements of certain body dimensions.To measure the total length (TL) of an ant it isnecessary to expand ants as much as possible, asmost specimens will preserve with the gaster bentventrally (in particular species in the genusTetramorium). Size ranges here refer to materialfrom Christmas Island and may not correspond tothe sizes reported for the same species elsewhere.

1. Mesosoma attached to gaster by single, distinctsegment (petiole) (Figures 2A-D); petiole canbe reduced and hardly visible (Figure 2C);gaster may be depressed between first andsecond segment, appearing like petiole andpostpetiole (Figure 20) 2

Mesosoma attached to gaster by two distinctsegments (petiole and postpetiole), gasteralways unconstricted between first andsecond segment (Figure 3) 30

petiole petiole

first segment. I petiole of gaster

~:e ) ~r}(~;~~o0)-~Y\

2C 2D q

KEY TO THE ANTS (WORKERS) OFCHRISTMAS ISLAND

The identification keys presented here will onlywork for ants considered part of the ChristmasIsland fauna (Table 1). Species introduced after the

vn,nwn number of ant species introduced to Hawaii(45 species, Reimer 1994) and nearly every otherbiogeographical region of the world (McGlynn1999). This is true, even when taking into accountthe possibility that a few of the species recorded onChristmas Island may be native, and that a fewspecies reported here were not collected during thecurrent survey and possibly no longer occur.Oceanic islands are reputed for supporting largenumbers of introduced species, and theirdepauporate native ant fauna is thought tocon tribu te to this condi tion (Simberloff 1995;Wilson and Taylor 1967). In addition, the proximityof Christmas Island to Indonesia (300km), and thefragmentation of Christmas Islands landscapethrough phosphorus mining may have facilitatedthe establishment of exotic ants. Studiesinvestigating the species richness of non-native taxahave shown that anthropogenic factors, such as thedegree of disturbance, fragmentation and proximityto the edge of the habitat fragment are oftenimportant factors influencing non-native speciesrichness (Brooks 1999; Byers 2002; With 2002).

Perhaps the greatest concern relating to theintroduced ant fauna on Christmas Island is thepotential for endemic species extinction. OnHawaii, the lack of co-evolved defenses of theendemic terrestrial fauna against exotic alien antshas resulted in drastic reductions in the nativeinvertebrate fauna (Reimer 1994). Similarly, onChristmas Island the Yellow Crazy Ant is having adevastating impact on the endemic Red Land Crab(O'Dowd et al. 1999), and is possibly affectingpopulations of the endemic subspecies of theground foraging Emerald Dove Chalcophaps indicanatalis Lister, 1889 and the endemic ChristmasIsland Thrush Turdus poliocephalus erythropleurusSharpe, 1887 (Davis 2002). With the exception of theRed Land Crab, the impact of A. gracilipes andother exotic ants on the native invertebrate fauna ofChristmas Island is unknown, but the potential lackof co-evolved defenses could make themparticularly vulnerable to extinction. For example,two potentially endemic spiders (Ariadna natalisPocock, 1900 and Heteropoda listeri Pocock, 1900)have not been found during recent targetedcollections, although they were considered commonwhen originally described (Pocock 1900).Undoubtedly, more experimental and observationalevidence is required to determine the effect of theseexotic ants on the native terrestrial fauna, inparticular in relation to invertebrates.


gaster

7. Large ant efL ca. 8.D mm), petiole dorsallydrawn into acute spine (Figure 74) ................................. OdontomacJws siJ)JjJIimLls

Medium sized (TL ca. 3.D mm), petiole summita narrow transverse ridge ......................... Anochetl1s sp. (graeHei group)

Small ant « 2mm in length), lower surface ofpetiole with translucent spot (fenestra)towards the front when viewed from the side(Figure 8) Ponera swezeyi

Larger (> 3.D mm), lower surface withoutfenestra 9

8.

7

8

fenestra

9. Petiole cylindrical, in dorsal and lateral viewlonger than wide (Figure 9) ...................... Platythyrea sp. (paraJIe!a group)

Petiole not cylindrical, generally wider thanlong in dorsal view 10

48

aCldipore

5A

antennalscape

row of spines

Upper surface of tip of gaster (pygidium) witha row of small spines (Figure SA); antennalscape short, only reaching about halfwayalong head (Figure 5B) ......................... 5 (Cerapachyinae: Cerapachys)

Upper surface of the tip of the gaster without arow of spines; scape longer than halfwayalong head 6 (Ponerinae)

4A4.

to the gaster (gaster separated from petioleonly by a shallow impression) (Figure 26),small ants « 2 mm in length), eyeless ........................... Amblyoponc zwall1~venbLlIgi

(Amblyoponinae)

3. Sting well developed and functional, andvisible in dead specimen (Figure 4A) 4

Sting absent, tip of gaster with a circular orsemicircular opening (acidipore) which isoften fringed with short setae (Figure 4B),or tip of gaster slit-like without fringe ofsetae 16

10 Tibia of hind leg with a single, comb-like(pectinate) spur I I (lfypoponera)

Tibia of hind leg with two spurs, one small,and a larger, comb-like (pectinate) one(Figure 10) 13

5. Eyeless, unicolourous reddish-brown ................................................. Cerapachys biroi

Well-developed compound eyes, bicoloured(head and gaster, excluding first segment,dark brown; trunk and petiole light brown;first segment of gaster bicoloured withposterior end dark brown) (Figure 24) ...................................... Cerapachvs !ongitarsLls

6. Head of bizarre, sculptured form (Figures 6A6) with mandibles linear and inserted near itsmidline 7

Head not deeply sculptured, mandiblesinserted at side of head (e.g. Figure 7) ......... 8

9 petiole

6A 68 10

54 V.W. Framenau, M.L. Thomas

21. Scapes surpassing occipital margin of the headby two-thirds their length or more (bestviewed from the side) (Figure 14A; alsoFigure 42), body elongate and thin .................................... Paratrechina Jongicomis

Scapes surpassing the rear margin of the headby less than half their length (Figure 14B; alsoFigure 40) 22

petiole

Antennae with 12 segments (including scape) ........................................................................... 20

~JCJ(T13A j::J W 138

18. TL ca. 5 mm; scape surpassing the rear marginof the head by two thirds their length ormore; yellow to light brown ants, bodyelongate, pronotum (first segment of trunk)longer than wide in dorsal view (Figure 33) ....................................... AnopJoJepis graciJipes

TL < 3 mm; scape surpassing the rear margin ofthe head by less than one quarter of theirlength, body compact, pronohlm shorte'r thanwide viewed dorsally 19 (PJagioJepis)

19. Antennal scape exceeds the occipital corner byat least the length of the first two funicularsegments combined PlagioJepis alluaudi

Antennal scape exceeds the occipital corner byless than the length of first furnicularsegment PJagioJepis exigua

20. TL < 3 mm; head, trunk [except propodeum (=third segment of trunk)] and gaster withdorsally prominent standing dark setae (onlythe small P. minutuJa has two setae onpropodeum), petiolar node inconspicuous,with only a low frontal face (Figure BA) ................................................. 21 (Paratrechina)

TL > 3 mm; head, trunk (including propodeum)and gaster with long, white but lessprominent setae, petiolar node conspicuous(Figure BB) 25 (Camponotus)

petiole

118

12B

11A

petiole

12A

14 Claws on hind-legs without teeth ....... PachycondyJa (Brachyponera) christmasi

Inner margin of claws on hind-legs with teeth.................................................. 15 (Leptogenys)

15. Mandibles slender and strongly curved at base(Figure l1A); petiole of similar height alongits whole length (Figure 12A) ........................................... Leptogenys falcigera

Mandibles wider and not curved at base(Figure lIB); petiole distinctly highertowards the rear when viewed from the side(Figure 12B) Leptogenys harmsi

1]. Antennal scapes short; when laid back alonghead they fail to attain median occipitalborder by a distance greater than theirmaximum diameter ............................... Hypoponera punctatissima

Antennal scapes longer, clearly attaining orsurpassing median occipital border 12

12. Dorsum of pronotum strongly shining andlacking punctuation; petiolar node in sideview distinctly narrowing dorsally (Figure68) Hypoponera con finis

Dorsum of pronotum dully shining, with aclose cover of very fine punctures; anteriorand posterior faces of petiolar node in sideview almost parallel ....................................... Hypoponera opaciceps

13. Eyes inconspicuous, less than 5 ommatidia ....... PachycondyJa (Trachymesopus) darwinii

Eyes conspicuous, more than 10 ommatidia .............................................................................. 14

16. Tip of gaster with a circular or semicircularopening (acidipore), often fringed with shortsetae (Figure 4B) 17 (Formicinae)

Tip of gaster slit-like, never with fringe of setae........................................... 27 (Dolichoderinae)

17. Antennae with 10 or 11 segments (includingscape) 18

14A 148


22. Small (1'1, = ].3 mm), propodeum (thirdsegment of trunk) with two setae,unicolourous light yellow-brown ................... Paratrechina sp. (minutu/a group)

Larger ants (TL ].5 mm), propodeum withoutsetae 23

23. TL ca. ].5 mm; body brown (gaster might besomewhat darker), coxae of leg 2 and 3distinctly lighter than trunk ......................................... Paratrechina vividu/a

peliole

petiole

Petiolar node greatly reduced, its forward faceabsent or indistinct (Figure ]8B) 28

17817A

18A

Body light brown to black (gaster might bedarker), coxae of leg 2 and 3 not distinctlylighter than trunk 24

24. TL ca. 2.5 mm, body uniformly dark brown toblack or light brown with darker gaster,katepisternum (cp. Figure] 5) with shortsetae Paratrechina sp. (bourbonica group)

1'1, ca. ].6 - 2.0 mm; body uniformly lightbrown, katepisternum without setae ........................... Paratrechina sp. (vaga group)

katepisternum

26. Length of antennal scape ca. 1.8-2.0 mm, setaeon antennae erect, single setae somewhatlonger (Figure] 7A) ................................... CamponotLls melichloros

Length of antennal scape ca. 2.3-2.5 mm; setaeon scape shorter, appressed and all of similarlengths (Figures 17B) ...... Camponotus sp. (novaehol/andiae group)

27. Petiolar node well developed, with distinctfrontal and rear faces, TL ca. 2 mm (Figure] 8A) Ochetel/us sp. (glaber group) Larger ants,TL > ].5 mm .

28 Larger ants (1'1, ca. 3 mm), unicolorous darkbrown to black Technomvrmex vitiensis

Very small ants (TL = 1.8 mm), light yellowbrown or bicoloured with dark brown headand trunk and light gaster (Figure 28) ...................................................... 29 (Tapinoma)

29. Head and trunk dark brown in contrast to lightgaster, legs and antennae (trunk sometimeslighter dOl'sally) (Figure 28), TL ca. ].5 mm ............................... Tapinoma me/anocepha/um

Unicolorous light yellow-brown, minute (TLca. 1 mm) Tapinoma sp. (minutum group)

30 Eyes absent Leptanil/a sp. (Leptanillinae)

Eyes present, generally conspicuous and withmany facets (ommatidia) (rarely with one ortwo ommatidia) 3] (Myrmicinae)

31. Antennae with /0-]2 segments (includingscape) 32

Antennae with a maximum of 6 segments(including scape) 50

32. Antennae 10-segmented, antennal club 2-segmented Solenopsis geminata

Antennae 11- or ]2-segmented, antennal club3-segmented or no distinct club 33

33. Propodeum without spim>s (Figure 19A) .............................................. 34 (AJononwrium)

Propodeum with one or two pairs of distinctspines (Figures 19B-C) 39

34. Very small ants, 1'1, < J.3 mm 35

propodeum

168

propodeum

15

TL < 4 mm; dorsal profile of propodeumconcave (Figure ]6A); apical segments ofantennae darker than rest of antennaeincluding scape Camponotus sp. (reticu/atusgroup)

TL > 5 mm; dorsal profile of propodeumconvex (Figure 16B); scape darker than apicalsegments of antennae 26

25.

16A

frontal cornerof petiole


20B


48. Body uniformly yellow-brown, palp formula(number of segments) 4,3 .................................. Tetramorium simillimum

Gaster darker than body, palp formula 2,2 ............................. Tetramorium cf. simillimum

49. In lateral view, mesometanotal groove absentor very weak (Figure 21 A), antennal clubdarker than seape; gaster black ................................. Cardiocondyla kagutsuchi

47. Body uniformly yellow-brown (very shiny indried specimens), petiole frontal face withindistinct frontal corner (Figure 20B); somesetae on front of head distinctly longer thandiameter of eyes Tetramorium insolens

Gaster darker than body (body not very shinyin dried specimens); frontal corner of petioledistinct (Figure 20C); setae on front of headshorter than diameter of eyes ................................. Tetramorium bicarinatum

45. Larger ants (TL > 2.0 mm); setae on trunkslender and acute 46

Smaller ants (TL < 2.0 mm), setae on trunkshort, thick and blunt 48

46. Body uniformly dark brown, frontal corner ofpetiole without a distinct edge (Figure 20A). Tetramorium pacificum

Body uniformly yellow-brown or yellowbrown and with darker gaster; frontal cornerof petiole more pronounced (Figures 20B-C).......................................................................... 47

Body pilosity less dense, setae never bifid ortrifid 45

44. Gaster black, distinctly darker than head andtrunk and with single setae that can be easilyrecognized individually ............................... Tetramorium lanuginosum

Gaster dark brown, of similar colour or slightlydarker than head and trunk and covered withdense, almost fur-like bifid and trifid setaethat can hardly be recognised individually ............................................. Tetramorium walshi


mesonotum

pronotumpropodeum

mesometanotalgroove

spine

19B

19C

propodeum

39 Pro- and mesonotum prominently roundedand markedly higher than propodeum inlateral view (Figure 19B) 40 (Pheidole)

Profile of trunk straight with at most a smallmesometanotal groove (Figure 19C) 41

40. Pronotum and top of head shiny ........................................ Pheidole megacephala

Pronotum and top of head strongly puncturedand rugose ..... Pheidole sp. (variabilis group)

41. Mesosoma and gaster with standing setae;distinct frontal carinae (longitudinal ridgesoriginating above antennae) extending almostto the posterior margin of head ................................................ 42 (Tetramorium)

No standing pilosity on head, mesosoma andgaster (setae appressed to body); frontalcarina shorter 49 (Cardiocondyla)

42. Antennae 11-segmented, postpetiole in dorsalview wider than petiole and its upper surfacesmooth and shiny Tetramorium smithi

Antennae 12-segmented, postpetiole in dorsalview ca. as wide as petiole and its uppersurface with pits 43

43. Fairly dense cover of silvery setae, some ofwhich are bifid or trifid (i.e. ends are split intwo or three) 44

37. Mandibles with 5 teeth. Monomoriwn latinode

Mandibles with 4 teeth 38

38 TL ca. 2 mm, head and trunk heavily punctuate................................... Monomorium pharaonis

TL ca. 3 mm, head and trunk not punctuate ....................................... Monomorium destructor

35. Head and gaster distinctly darker thanmesosoma Monomoriwn floricola

Head and gaster of similar colour as mesosoma.......................................................................... 36

36. Reduced eyes with only 1-2 ommatidia ............................. Monomorium cf. subcoecum

Eyes normally developed, eyes with > 10ommatidia Monomorium orientale

56

19A


In lateral view, mesometanotal groove distinct(Figure 2] B); antennae uniformly coloured;gaster light brown .............................. Cardiocondyla wrollghtonii

mesometanotal groovemesometanotal groove

21A

50. Mandibles linear, meeting only at their tips,inner margins without teeth ................................................. 51 (Strumigenys)

Mandibles triangular, meeting along their innermargins which are toothed ..................................... Pvramica membrani{era

51. Antennae with 4 segments (including scape) ............................................. Strllmigenys emmae

Antennae with 6 segments (including scape) ....................................... Strumigenys godeHroyi

ANTS OF CHRISTMAS ISLAND

All currently reported ant species are listed herewith comments on their identification, ecology, anddistribution on Christmas Island and worldwide.Subfamilies, genera within subfamilies and specieswithin genera are listed in alphabetical order.

Family Formicidae LatreiIle, 1809

Subfamily Amblyoponinae Bolton, 2003

Genus Amblyopone Erichson, 1842Members of the genus Amblyopone are specialist

predators on certain arthropods; some show a strongpreference for centipedes (Shattuck 1999). They livein soil or leaf litter (Wilson and Taylor 1967).

Amblyopone zwaluwenburgi (Williams, 1946)

IdentificationVery small (TL < 2mm); eyeless (Figure 22); single

petiole is attached to gaster with its whole rear face(Figure 213).

Figure 22 Head of Amblvopont' zwaluwt'nburgi(redrawn after Wilson and Taylor ]')67).

N

AFigure 23 Records of Amblyopone zwaluwenburgi on

Christmas Island .

DistributionChristmas Island: The presence of A.

zwalllwenbllrgi on Christmas Island is based on thereport of a single winged queen collected in 1989without precise locality data (Taylor 1990) andsome recent (2001-2002) collections at the CentralArea Workshop, Stuart Hill and Western CircuitRoad (Figure 23) (D. O'Dowd personalcommunication). Given that A. zlvaluwenburgi is atiny cryptobiotic species that is especially difficultto collect (Wilson and Taylor 1967), the absence of itin the current surveys probably reflects thecollection methodology rather than itsdisappearance from the island.

Worldwide: Prior to the record from ChristmasIsland, A. zwaluwenbwHi was only known fromHawaiian sugar cane fields (Taylor 1990). However,this species is a likely introduction to Hawaii andChristmas Island and is possibly native toMelanesia or the East Indies (Brown ]960; Wilsonand Taylor 1967).

Subfamily Cerapachyinae Forel, 1893

Genus Cerapachys Smith, 1857

Species of Cerapachys are specialist predators ofother ants. During raids on ant nests, larvae in theattacked nest are stung and paralysed but not killed.\Vhen returned to the host nest, paralysed larvaecan remain in this state for extended periods of timewithout increasing in size or pupating (Shattuckand Bennett 200]). Nests are generally small,normally containing only a few hundred workersor less. Most species will disperse quickly whendisturbed (Shattuck 1999).


Cerapachys biroi Forel, 1907

IdentificationTL ca. 2.5 mm; eyeless; unicolorous reddish

brown.

BiologyIn colonies of C. biroi collected in Japan and

Taiwan, there are no queens or sterile caste (Ravaryand Jaisson 2004). Instead, unmated femalt:>individuals lay diploid eggs (thelytoky) (e.g. Ravaryand Jaisson 2004). Reproduction is linked to atemporal polyethism, in which older workers ceaseto lay as they become foragers, and a morphologicalpolyethism, illustrated by two morphological typesthat are differentiated by differences in taskallocation and ovary capacities (Ravary and Jaisson2004).

DistributionChristmas Island: The distribution of C. biroi on

Christmas Island remains obscure. It was reportedby Taylor (1990) without detailed locality data andnot collected during the recent surveys.

Worldwide: Cerapachys biroi is Widespread intropical Asia and has also been introduced toPolynesia and the West Indies (e.g. Ravary andJaisson 2004).

Cerapachys longitarsus (Mayr, 1879)

IdentificationTL ca. 2.0 mm; eyes well developed; distinctly

bicoloured, with darker head and posterior parts ofgaster (Figure 24).

BiologyIn general, species of Cerapachys nest directly in

the soil with single, small, simple entrance holes.

Figure 24 Worker of Cerapachys longitarslls.

Figure 25 Record of Cerapachys longitarslls onChristmas Island.

However, Cerapachys longitarsus commonly nestsin hollow twigs (Brown 1975) and this nestingbehaviour may have facilitated its dispersal.

DistributionChristmas Island: A single male was reported by

Taylor (1990) without locality data. During the IWS2005, two workers from a single waypoint in thesouthern part of the island were collected in clearedland (Figure 25).

Worldwide: Cerapachys longitarsus iswidespread in the Indo-Australasian region(Shattuck and Bennett 2001).

Subfamily Dolichoderinae Forel, 1878

Genus Ochetellus Shattuck, 1992

Ochetellus sp. (glabergroup)

Nominal speciesOchetellus glaber (Mayr, 1862) (Black House Ant)

IdentificationTL ca. 2 mm; petiolar node well developed and

very narrow in lateral view (Figures 18A, 26). Thetaxonomy of 0. glaber and allied species is notsolved and therefore this species must be regardedas representing a species group.

BiologyIn New Zealand, 0. glaber has been reported to

forage primarily arboreally (Manaki WhenuaLandcare Research 2006), although this appears tobe an exception to its generally epigaeic life style(A. Andersen personal communication).


1 mm Figure 28 Worker of Tapinoma meIanocephalum.

Figure 26 Worker of Ochetellus sp. (glaber group).

N

AFigure 27 Records of OcheteJIus sp. (glaber group) on

Christmas Island.

DistributionChristmas Island: Ochetellus sp. (g/aber group)

was only found around the main settlement areaand near the new Immigration Reception andProcessing Center (IRPC) in the northwestern partof the Island (Figure 27). This restricted distributionmay reflect a relatively recent introduction toChristmas Island.

Worldwide: The nominal species, 0. g/aber, ismost likely native to Australia, and has beenintroduced to the Pacific islands (including Hawaii)(Reimer 1994), North America (Smith 1979) andNew Zealand (Brown 1958).

Genus Tapinoma Forster, 1850

Tapinoma melanocephalum (Fabricius, 1793)(Ghost Ant)

IdentificationEasily recognised by its small size efL ca. 1.5 mm)

and peculiar colouration: head and trunk are deepdark brown (trunk sometimes lighter dorsally) withgaster and legs opaque or milky white (Figure 28).

BiologyThis species is an opportunistic nester utilising

almost any crack or crevice, such as tufts of deadbut temporarily moist grass, plant stems, andcavities beneath detritus in open, rapidly changinghabitats (Hblldobler and Wilson 1990). Tapinomame/anocepha/um is unlikely to have any significantecological impact (A. Andersen personalcommunication), but can be a general nuisance inurban areas (ISSG 2004). Its ecological impact inmore natural environments is unknown.

DistributionChristmas Island: Despite its small size and

somewhat cryptic colouration, T. me/anocepha/umwas recorded at nearly 30'Xl of the sites visitedduring the IWS 2005 (Figure 29). It was one of theearliest recorded species on Christmas Island (Table1). The Ghost Ant was collected in both disturbedareas, such as mine sites, and n,ore natural forestedenvironments.

Worldwide: Tapinoma me/anocephalum is atramp ant and is widely distributed in the tropicaland subtropical regions of the world. It is probablyof African or Oriental origin (Wheeler 1910).

:-...' ...... ~.~.. '.••.:.~~,;!.

.' •• "'~c.... ..••••..... ...:.

Figure 29 Records of TapinoIl1d melanocephalllIl1 onChristmas Island.

60

Tapinoma sp. (minutum group)

Nominal speciesTapinoma minutum Mayr, 1862 (Tiny Ghost Ant)

IdentificationEasily distinguished from T. melanocephalum by

the uniform yellowish-brown colour pattern.Shattuck (1999) lists the nominal and threesubspecies of T. minutum in Australia suggestingthat this species group requires taxonomic revision.There are several to many species of the Tapinomaminutum group in Australia (A. Andersen personalcommunication).

DistributionChristmas Island: This species was recorded at

only four sites during the IWS 2005 (Figure 30).These sites are widely distributed across the island,but three out of the four are very close to roads,suggesting that its dispersal on Christmas Islandmay be primarily through human means. However,this species is very inconspicuous and it is highlyprobable that it was overlooked at a large numberof sites.

Worldwide: The nominal species, T. minutum,was originally described from Sydney (New SouthWales) and must be considered an Australian native(Shattuck and Bennett 2001). Wilson and Taylor(1967) report this species from Queensland(Australia), Samoa, New Guinea, Solomon Islands,Fiji and Micronesia.

Figure 30 Records of Tapinoma sp. (minlltllm group)on Christmas Island.


1 mm

Figure 31 Worker of Technomyrmex vitiensis.

Genus Technomyrmex Mayr, 1872

Technomyrmex vitiensis Mann, 1921

IdentificationTL ca. 3 mm; its larger size and uniform dark

brown to black colouration distinguish this speciesfrom Tapinoma sp. (Figure 31).

Technomyrmex vitiensis is currently listed asjunior synonym of T. albipes (Wilson and Taylor1967); however a forthcoming revision of the genusTecl1l1omyrmex recognises it as a valid species (B.Bolton personal communication). Therefore, we listthe species here in its new unpublishedcombination. Previous records of T. albipes fromChristmas Island must be attributed to T. vitiensis(see Table 1).

BiologyOne of the characteristics of the species group to

which T. vitiensis belongs is the development ofworker-queen intercastes. These are worker-likeindividuals, which exhibit a series of increasinglygyne-like morphological developments, such as thepresence of ocelli, spermathecae and a graduallymore gyne-like mesosomal structure. Theseintercastes can undertake reproductive behaviour(Yamauchi et al. 1991).

..

Figure 32 Records of Technomyrmex vitiensis onChristmas Island.


DistributionChristmas Island: Although it is well dispersed

across the island, T. vitiellsis was recorded at lessthan 10'1;) of waypoints (Figure 32). During the IWS2005, it was collected primarily at the edge ofdisturbed habitats.

Worldwide: It is currentlv difficult to establish theworldwide distribution of T. viliensis due to theconfusion of this species with T. albipes. Ilowever,it appears to be a very successful tramp species andhas colonised many islands in the Pacific and IndianOceans (B. Bolton personal communication).

Subfamily Formicinae Latreille, 1809

Genus Anoplolepis Santschi, 1914

Anoplolepis gracilipes (Smith, 1857)(Yellow Crazy Ant, Long-Legged Ant) (not to beconfused with the Black Crazy Ant, Paratrechina

longicomis (see further below)).

IdentificationTL ca. 5 mm; unmistakable (Figure 33); long

slender gracile body with long legs, yellowbrownish colouration, gaster usually somewhatdarker than head and thorax; workersmonomorphic.

RemarksAnoplolepis gracilipes was probably introduced

onto Christmas Island some time between 1915 and1934 (Donisthorpe 1935; O'Dowd et al. 1999), but itsdistribution was unknown until populationsexploded in the early 1990s causing devastatingeffects on the Red Land Crab population. Since1996, efforts have been made to locate high-densitysites of the Yellow Crazy Ant for managementpurposes. This species is currently the focus of amulti-million dollar control program administeredby PANCl. Curiously, A. graciJjpes was notreported between 1935 and 1989, suggesting lownumbers on Christmas Island during this period.Note that most literature on A. gracilipes is underits junior synonym A. longipes.

Figure 33 Worker of Anoplolcpis gracilipcs.

61

Figure 34 Records of AIJoplolcpis gracilipes onChristmas Island.

DistributionChristmas Island: Although A. graciJjpes is

generally associated with human-modifiedenvironments in other parts of its introduced range,on Christmas Island it also thrives in (previously)undisturbed native forest habitats. It is widespreadand common on the island (Figure 34).

Worldwide: Anoplolepis gracilipes has beenintroduced widely across the globe (McGlynn1999). However, it remains poorly studied and evenits native range is not certain. It may haveoriginated from Africa or Asia (Holway et al. 2002;Wetterer 20(5). 'The center of diversity for thisgenus is Africa and A. gracilipes is the only speciesdistributed beyond that continent.

Genus Camponotus Mayr, 1861Species of Campollotus are polymorphic and can

show considerable size variation within singlespecies. Foraging tinIes vary, with some speciesforaging nocturnally or noctidiurnally (Shattuck1999). As it is difficult to obtain detailedinformation on the biology of most Camponotusspecies found on Christmas Island, it is possiblethat the distribution of these species isunderrepresented by the collection methodologyused in the IWS 2005. Camponotus species mayforage predominantly at night C. \'ariegatus inHawaii (Rei mer 1994)).

Camponotus sp. (reticulatus group)

Nominal speciesCal7lpOllotus retieulatus Roger, 1863

62

Figure 35 Worker of Camponotlls sp. (reticllJatllsgroup).

Figure 36 Records of Camponotlls sp. (reticllJatllsgroup) on Christmas Island.

IdentificationSmallest Camponotus on Christmas Island (TL ca.

3.5 mm) and easy to recognise; propodeum concavedorsally (Figures 16A, 35). Workers of this speciesare very similar to Camponotus mackayensis (seefor example McArthur and Shattuck 2001), howeversoldiers differ considerably (A. Andersen personalcommunication).

DistributionChristmas Island: Although well dispersed across

the island, this species is not common and wasfound at only 3% of waypoints (Figure 36).CamponotlIs sp. (reticulatlIs group) does not appearto show any particular preference for certainhabitats, but is not found in highly disturbed minesites.

Worldwide: Unknown.

Camponotus melichloros Kirby, 1888

IdentificationTL ca. 6-8 mm; easily confused with Camponotl1s


1 mm

Figure 37 Worker of CampOl1otlls melich/oros.

sp. (novaehollandiae group), but differs by the setaeon the antennal scape which are more erect than inCamponotlIs sp. (novaehollandiae group); C.melichloros is also somewhat smaller than C. sp.(novaehollandiae group) and with an overall lighterhead (but the latter two characters are not reliablein differentiating both species) (see Figure 37).

CamponotlIs melichloros was originallydescribed from Christmas Island. It is the onlyspecies of the C. maclIlatlIs group on ChristmasIsland. Minor workers of this group have widerheads at the front than at the back whereas the headof major workers is wider at the back than at thefront. Previous listings from Christmas Island forspecies of this group include C. chloroticlIS(Collingwood and Hedlund 1980) and C. maclIlahls(Abbot 2006). Collingwood and Hedlund (1980)discuss the identity of this species on ChristmasIsland: 'Camponorns chloroticlIS listed above maywell be the same as C. melichloros [...] but with ageneralised description that would equally fit bothC. chloroticlIS and the widespread C. variegatlIs.We list this widespread species of the maculatlIsgroup from Christmas Island as C. melichlorospending a revision of the maculatlIs group for theIndo-Australian region.

DistributionChristmas Island: Camponotus melichloros is one

Figure 38 I\ecords of CampOl1otlls melich/oros onChristmas Island.


of the most common ants of Christmas Island,having been found at 27'X, of sites surveyed (Figure38). It is distributed widely across the island, butappears to prefer forested sites to open disturbedhabitats such as minefields.

Worldwide: This species appears to be commonin the lndo-Australian region (Taylor 1990).

Camponotus sp. (novaehoJIandiae group)

Nominal speciesCamponotus novaehollandiae Mayr, 1870(Northern (Common) Sugar Ant)

IdentificationTL ca. 7-9 mm; easily confused with C.

melichloros, but differs by the orientation of thesetae on the scape, which are less erect than in C.melichloros, the relatively larger size (but sizesoverlap) and overall darker colour of the head (butcolour may overlap).

RemarksIn Australia, the nominal species of this group, C.

novaehoJlandiae, forages noctidiurnally, so itsdistribution may be underrepresented by themethodology used in the current study (Shattuckand Bennett 2001).

DistributionChristmas Island: This is the first record of a

Camponotus species of the novaehollandiae groupon Christmas Island. This species is relativelyuncommon, found at only eight waypoints. Itscurrent distribution appears to reflect a recentintroduction, being found exclusively in the NorthEast region of the island near the main port of entry,Flying Fish Cove (Figure 39).

N

AFigure 39 Records of Camponotlls sp. (novaehollandiae

grou p) Oil Christmas bland.

63

Worldwide: Members of this species group arealso known from throughout northern Australia(Shattuck and Bennett 20(1), and Papua NewGuinea (Edwards and Thornton 2001).

Genus Paratrechina Motschoulsky, 1863With the exception of P. rninutula (to species

group level) and P. longicornis, the identification ofworkers in the genus Paratrechina is notoriouslydifficult, in particular as the systematics andtaxonomy of this genus are not well resolved (B.Bolton personal communication). Speciesidentification must be treated cautiously and inparticular, those that key out to P. bourbonica mayrepresent a different species. A worldwide revisionof the genus that will consider material fromChristmas Island is in progress (}. LaPolla personalcommunication).

Paratrechina sp. (bourbonica group)

Nominal speciesParatrechina bourbonica (Fore\, 1886)

IdentificationTL ca. 2.5 mm. The more common Paratrechina

sp. (bourbonica group) (Figure 40) and fairly rareParatrechina sp. (vaga group) are very difficult todistinguish, in particular when only singleindividuals are available. Wilson and Taylor (1967)diagnosed P. bourbonica and P. vaga occurring onPacific Islands merely by size and, to some extentcolouration, but admitted that these characters mayoverlap. Newly eclosed Paratrechina sp.(bourbonica group) may be lighter in colourationand resemble Paratrechina sp. (vaga group). It issuggested, that for identification, whole nest seriesshould be considered. Reimer (unpublished) usedan additional character to differentiate both speciesin Hawaii, namely the presence (P. bourbonica) andabsence (P. vaga) of setae on the katepisternumwhich was used here to distinguish between thetwo species groups. On Christmas Island, it appearsthat there may be more than one species in whatkeys out to Paratrechina sp. (bourbonica group).

/'1 mm

Figure 40 'vVorker of l'aratrechina sp. (bollrbonicagroup).


Figure 41

N

ARecords of Paratrechina sp. (bourbonicagroup) on Christmas Island.

1 mm

Figure 42 Worker of Paratrechina longicomis.

IdentificationTL ca. 2.5 mm. Paratrechina longicomis is easily

distinguished from other Paratrechina species onChristmas Island by its extremely long antennalscapes (Figure 42) and legs.

Some specimens are unicolourous dark black,whilst other are lighter with a darker gaster.However, pending a revision of Paratrechina (J.LaPolla personal communication), we have notdifferentiated between these forms.

BiologyOn Hawaii, P. bOllrbonica has been found in

disturbed montane habitats such as roadsides orurban development sites, but never in undisturbedsites (Reimer 1994). On Samoa it favors moredisturbed habitats than either P. minlltula or P. vaga(Wilson and Taylor 1967). These habitat preferencescontrast strongly with this species' widespreaddistribution in natural forested areas on ChristmasIsland.

DistributionChristmas Island: Paratrechina sp. (bourbonica

group) is one of the most common and Widespreadspecies on Christmas Island (Figure 41), but it isgenerally not found in mine sites.

Worldwide: Probably originating from the Oldworld tropics (Asia) (Deyrup et al. 2000; Wilson andTaylor 1967), the nominal species, P. bourbonica,has been spread by commerce throughout theIndian and Pacific Oceans and the New Worldtropics (Trager 1984; Wilson and Taylor 1967).However, a proper assessment of P. bOllrbonica'sglobal spread may have to await taxonomic revisionof this species.

Paratrechina longicornis (Latreille, 1802)(Black Crazy Ant)

BiologyParatrechina longicomis is an extremely hardy

species that is highly adaptable and can live in bothvery dry and highly moist environments (ManakiWhenua Landcare Research 2006). Its ability toinvade different habitats, together with its capacityto displace other ants and possibly otherinvertebrates (ISSG 2004), makes this species aserious threat to Christmas Island's ecosystems. OnChristmas Island it currently appears to berestricted to disturbed areas, but has the potentialto spread into more natural environments.Unfortunately, this species has proven relativelydifficult to control because workers forage longdistances and their nests are difficult to locate (ISSG2004).

Figure 43 Records of Paratrechina longicornis onChristmas Island.


DistributionChristmas Island: On Christmas Island, l'.

/ongicomis is primarily associated with disturbedhabitats such as mine fields and near humansettlements and roads (Figure 43).

Worldwide: Paralrechina /ongicomis is either ofAsian or African origin (Smith 1965; Trager 19R4). Itis one of the most common tramp ants in the tropicsand subtropics, and has probably achieved one ofthe widest distributions of all the tramp ants(Manaki Whenua Landcare Research 2(06).

Paratrecltina sp. (minutula group)

Nominal speciesParatrechina minutu/a (Fore!, 19(1)

IdentificationSmallest of all Paratrechina species from

Christmas Island (n" ca. 1.0 1.2 mm); Wilson andTaylor (1967) considered Paratrechina minlltll/a asa species complex with 'the only character showingvariation of possible species significance [... 1 issize". However, differences in head width ofdifferent populations did not appear to warrantspecific separation. Andersen (2000a) reported theminutula group distributed throughout Australia,with about a dozen species occurring in themonsoonal region. Therefore, this species must beconsidered to represent a species complex pendingrevision of the group.

DistributionChristmas Island: Paratrechina sp. (minlltu/a

group) is one of the most common species onChristmas Island. It is widespread across the island,

" ('\ .•

N

A

65

but appears to show a preference for forestedhabitats on the plateau (Figure 44).

Worldwide: It is difficult to judge the worldwidedistribution of J'. minutu/a and allied species, as itrepresents a complex of species. Ilowever, thisgroup is most likely native to the Indo-Australianregion (Wi lson and fay lor 1967). The type localityof the nominal species is New South Wales, but itappears to occur throughout Australia.

Paratrecltina sp. (vaga group)

Nominal speciesParatrechina vaga (Forel, 19(1)

IdentificationDiffers from Paratrechina sp. (bourbonica group)

in size (TL ca. 1.6 - 2.0 mm) and colouration (seeabove). The coxae of legs 2 and 3 are of similarcolour as the trunk (brown), not distinctly lighter

in V vividu/a).

DistributionChristmas Island: Paratrechina sp. (vaga group) is

widely dispersed across the island, but was notcommonly found as part of the ant fauna during theIWS 2005 (Figure 45)

Worldwide: The nominal species, P. vaga, isreported to be native to New Guinea and theWestern Pacific (Manaki Whenua LandcareResearch 20(6). Species of this complex are reportedfrom tropical Australia (Andersen 2000a) andvarious Pacific Islands, including Hawaii (Wilsonand Taylor 1967). Also reported from Madagascarand Galapagos (Manaki Whenua Landcare I\esearch2(06).

N

,\Figure 44 Records of Paratrcchina sp. (minutula group)

on Christmas Island.Figure 45 Records of Paratrcchina sp. (vaga

Christmas Island.on

66

Figure 46 Records of Paratrechina vividula onChristmas Island.

Paratrechina vividula (Nylander, 1846)

IdentificationWorkers relatively small (TL ca. 1.5 mm), weakly

bicoloured with the head and gaster yellowishbrown to black and alitrunk, legs and antennaeyellow to dark reddish-brown. Paratrechinavividula differs from other Paratrechina ofChristmas Island, in particular the similar sizedParatrechina sp. (vaga group), by the lightcolouration of the coxae of legs 2 and 3.

DistributionChristmas Island: On Christmas Island this

species is primarily found on the plateau neardisturbed areas such as roads or mine fields (Figure46).

Worldwide: Native to North America this specieshas spread relatively widely outside its native range(Trager 1984).

Genus Plagiolepis Mayr, 1861Plagiolepis include small, inconspicuous ants that

nest in soil and under rocks or logs or in rottenwood on the ground. Two Plagiolepis species havebeen recorded from Christmas Island, P. al1uaudiand P. exigua (Collingwood and Hedlund 1980),but were not encountered during the recentsurveys. It is possible they were overlooked becauseof their inconspicuous nature and small size(Shattuck 1999) and their preference to nest in oraround human dwellings. PlagioJepis are similar ingeneral appearance to the dolichoderine Tapinoma,but have only 11 antennal segments instead of 12.Both Plagiolepis listed here are well-known trampspecies (Wilson and Taylor 1967).

v.w. Framenau, M.L. Thomas

Plagiolepis alluaudi Forel, 1894

IdentificationTL ca. 1.5 - 2.0 mm; differs from P. exigua by a

longer scape that exceeds the occipital corner by atleast the length of the first two funicular segmentscombined (by less than the length of the firstfurnicular segment in P. exigua)

DistributionChristmas Island: The presence of this species on

Christmas Island is based on an unpublished reportwithout precise locality data (Collingwood andHedlund 1980). Plagiolepis al1uaudi was not foundduring the recent surveys.

Worldwide: Plagiolepis al1uaudi is a pantropicaltramp species with an increasing range throughtransport by human commerce. It appears to benative to Africa (Wilson and Taylor 1967).

RemarksIn Hawaii it is commonly found in the dry, mesic,

and wet lowland communities (Reimer 1994).

Plagiolepis exigua Forel, 1894

IdentificationTL ca. 1.5 - 2.0; differs from P. al1uaudi by its

shorter scape (see above), sparser pilosity (presenceof setae) and shinier body surface (Wilson andTaylor 1967).

DistributionChristmas Island: Similar to P. al1uaudi, the

presence of P. exigua on Christmas Island is basedon the report by Collingwood and Hedlund (1980).It was not collected during recent surveys.

Worldwide: It is known from India, westernChina, Hong Kong, Madagascar and Ethiopia(Wilson and Taylor 1967). Early records fromHawaii are possibly erroneous (Wilson and Taylor1967).

Subfamily Leptanillinae Emery, 1910The subfamily Leptanillinae includes only seven

genera and is entirely absent from the New Worldand has not yet been discovered in the Malagasyregion (Bolton 1994). These ants are very rarelyencountered and little is known about their biology.

Genus Leptanilla Emery, 1870

Leptanilla sp_

IdentificationMinute ants (Taylor 1990), eyes absent (Brady and

Ward 2005); petiole and postpetiole present.


BiologyThe majority of species within Leplanilla are

described from either isolated males or workers(Brady and Ward 2005). Most males are caught intraps or by sweeping, suggesting that they leave thenest for mating (Masuko 1990). Leptanilla queenshave an unusual feeding behaviour in which theyimbibe hemolymph from a pair of specialised ductorgans on the larvae. I"arval hemolymph feeding bythis genus may be an adaptation to unstable foodconditions (Masuko 1990).

DistributionChristmas Island: A Leplanilla sp. was reported

by Taylor (1990) from a single male specimen. Nolocality data was given. Workers of this genus havenever been collected from Christmas Island. Wc didnot find any LeptaniIla sp. in the current survey;however this is not surprising given thesubterranean nature of this genus (Masuko 1990).

Worldwide: LeplaniJIa sp. are known fromworkers collected in North Africa, the IndoAustralian area and Japan (Taylor ]990).

Subfamily Myrmicinae Lepeletier, 1835

RemarksRepresentatives of the Myrmicinae are

distinguished from all other ants of Christmas Islandby the presence of two segments, a petiole and apostpetiole, connecting the trunk and the gaster. Theonly other subfamily with similar morphology onChristmas Island is the Leptanillinae, small crypticand blind ants that are known from Christmas Islandonly from a single male specimen of LeplaniIla(Taylor 1990). All other ant subfamilies with petioleand postpetiole (Aenictinae, Ecitoninae,Leptanilloidinae, Myrmeciinae, Pseudomyrmecinae)do not currently occur on Christmas Island.

Genus Cardiocondyla Emery, 1869Species of this genus are most easily recognised

by their dorsoventrally flattened, wide postpetiole.When viewed from above it is much wider thanlong and broader than the petiole. A recentrevisionary studv of CardiocondvJa allows accuratespecies identification for the representatives of thisgenus on Christmas Island (Seifert 2003).

The males of some CardiocondyJa species areunusual. In most ants, males are fully winged.However, in both CardiocondyJa species found onChristmas Island, males can be wingless (ergatoid)and worker-like (Seifert 2003).

Cardiocondyla kagutsuchi Terayama, 1999

IdentificationTt ca. 1.5 ~ ].8 mm; mesometanotal groove III

67

N

AFigure 47 Records of Cardiocondvla kaglltslIchi on

Christmas Island.

lateral view absent or only very shallow (Figure21 A). On Christmas Island, this species haspreviously been misidentified as C. nuda (TayIor1990; Table 1), which differs in the relative height ofpetiole and postpetiole (Seifert 2003). It is a sisterspecies of, and may be conspecific with, C.mauritanica Forel, 1890, a common cosmotropicaltramp species (Seifert 2003).

DistributionChristmas Island: CardiocondyJa kagutsuchi can

be found interspersed across the island but isprimarily restricted to disturbed habitats such asminefields and roads (Figure 47).

Worldwide: The range of C. kagutsuchi extendsover East India, Sri Lanka, Nepal, Bhutan, southernChina and South Korea, southern Japan, Guam,Singapore, Malaysia, Indonesia, the Philippines,Flawaii and Papua New Guinea (Seifert 20(3).

RemarksThe distribution of C. kagutsuchi on Christmas

Island agrees with the habitat preferences describedin the literature, i.e. 'in shallow soil in open,disturbed areas with bare or weaklv herbaceousground' (Seifert

CardiocondyJa wroughtonii (Forel, 1890)

DescriptionTL ca. 1.3 1.5 mn.; differs from C. kagutsuchi

the presence of a distinct mesometanotalgroove (Figure 2113) and the colour pattern (seekey above). The postpetiolar sternite has aprominent anterolateral corner that is absent inC. kaglltslIchi.

68

•

•

Figure 48 Records of Cardiocondyla wroughtonii onChristmas Island.

DistributionChristmas Island: Cardiocondyla wroughtonii is

widespread across the plateau of the island and alsofound on the northern terraces (Figure 48). Thisspecies appears to prefer more forested habitatsthan C. kagutsuchi on Christmas Island.

Worldwide: Cardiocondyla wroughtonii is apantropical tramp species. It was thought to haveoriginated in tropical Africa and to have extendedits range very widely in the tropics and subtropicsthrough human agency (Wilson and Taylor 1967),but more recent evidence suggest it to be native toAustralia (A. Andersen personal communication).

Genus Monomorium Mayr, 1855Five species of Monomorium have been

previously reported from Christmas Island; M.australicum (as M. talpa), M. destructor, M.f1oricola, M. latinode and M. pharaonis (Table 1).Only two of these, M. f1oricola and M. latinode, andtwo additional species (M. orientale and M. cf.subcoecum) were collected during the recentsurveys. The absence of M. destructor and M.australicum could be based on misidentification bypast researchers. Monomorium destructor is verysimilar to M. latinode, and M. australicum is almostcertainly the species that is here identified as M. cf.subcoecum (see Heterick 2001). However, we haveincluded M. destructor here, since it is a wellknown cosmopolitan tramp species. The absence ofM. pharaonis in recent surveys is not so easilyexplained. This species is a well-known tramp thatwas reported fairly early from Christmas Island(Donisthorpe 1935). Since there have been nosubsequent reports of this species on ChristmasIsland, it is likely that it either never occurred on


the island, has become locally extinct, or is onlypresent in and around houses (as in other parts ofits introduced range) and was therefore notcollected during the recent surveys. Accuratespecies identification of members of Monomoriumis possible by applying the keys of Bolton (1987)and Heterick (2001).

Monomorium destructor (Jerdon, 1851)(Singapore Ant)

IdentificationSize variable (TL ca. 1.8 - 3.5mm). This species

was not collected during the current survey. It ispossible that the two reported cases of M.destructor on Christmas Island (Collingwood andHedlund 1980; Donisthorpe 1935) weremisidentifications, since M. destructor is verysimilar to M. latinode in both size and coloration.Monomorium destructor is distinguished from M.latinode by the presence of 4 teeth on eachmandible (versus 5 in M. latinode), the distinctmetanotal groove (shallow and indistinct in M.latinode) and the narrower postpetiole (1.5 times aslong as broad in M. latinode) (Manaki WhenuaLandcare Research 2006). Monomorium destructoris also highly polymorphic, with minor workers 2mm or less in length (A. Andersen personalcommunication).

DistributionChristmas Island: Unknown, based on previous

reports without precise locality data (Table 1).Worldwide: Monomorium destructor is most

likely of Indian origin and has been introducedthroughout the tropical zone, and increasingly intotemperate regions (Bolton 1987).

RemarksMonomorium destructor has been considered a

pest species in Australia since the 1970s (Davis et al.1993). This species is known to cause significantcommercial damage. It can gnaw holes in fabric andrubber goods and is able to remove insulation frompower and phone lines and damage polyethylenecable (Bolton 1987). Several fires are attributed tothese ants (Davis and van Schagen 1993). There areeven reports of people being bitten or stung fiercelywhile in bed (Smith 1965).

Monomorium floricola (Jerdon, 1851)

IdentificationMonomorphic, TL ca. 1.4 mm; bicoloured with

light brown trunk, and much darker head andgaster. Its small size and striking coloration easilydistinguishes this ant from other ant species onChristmas Island.


•

.

N

A

69

N

/\Figure 49 Records of i\1onomoriuIJ1 fIoricola on

Christmas Island. Figure 51 Records of i\1onomoriuIJ1 Iatinode onChristmas Island.

DistributionChristmas Island: Despite this species being

reported on the island since 1935 (Table 1), itsdistribution is largely restricted to areas adjacent toroads (Figure 49). This pattern is consistent with itsdistribution in other parts of its introduced range,where colonies seem unable to penetrateundisturbed native forests (Wilson and Taylor1967). However, it should be noted that this speciesis primarily arboreal (Smith 1965; Wilson andTaylor 1967) and may have been overlooked atmany forested sites using the hand collectionmethod utilised in the IWS 2005.

Worldwide: Monomorium f1oricola is possiblynative to tropical Asia (Wilson and Taylor 1967),but is an extremely successful tramp species that iswidespread in tro~;ical and subtropical regions.

Monomorium latinode Mayr, 1872

IdentificationTL ca. 2.5 mm; postpetiolar node viewed from

above wider than petiole. This species is similar toM. destructor in size and coloration, but the 5-

Figure 50 \Norker of ;'vfonomorium Iatinode.

toothed mandibles and shallow mesometanotalgroove distinguish Iv1. latinode (Figure 50).

DistributionChristmas Island: The current distribution of this

species is restricted to the northeastern region ofthe island (Figure 51). This distribution appears toreflect a relatively recent introduction (Table 1).

Worldwide: Monomorium latinode is most likelynative to the Indian subcontinent (Bolton 1987),although Wilson and Taylor (1967) report its nativerange as 'Sri Lanka to Taiwan and south to Java andSumatra'. It is known from several countflesbordering the Indian Ocean (Bolton 1987). Itspresence in Borneo, 'ranzania and New Zealandindicates its potential as a tramp species.

Monomorium orientale Mayr, 1879

IdentificationVery small ant (Tt ca. 1.] nun); could be confused

with '/'lv1. cf. subcoecum, but Ihe latter has veryreduced eyes, whereas the eyes of i'v1. orientale arefully developed with more than 10 ommatidia.

DistributionChristmas Island: This is the first record of this

species on Christmas Island. It was only fl'portedfrom one waypoint in the northeastern corner ot till'island (Figure 52).

vVorldwide: A1onomorium orientale hasoriginally been described from India (McClynn1999). It has subsequently been reported tromAustralia (B. lieterick, personal communication)and New Zealand but the latter records may Iwerroneous Cunawardana

70

Figure 52 Records of Monomorillm oriental/:' onChristmas Island.

Monomorium pharaonis (Linnaeus, 1758)(Pharaoh Ant)

IdentificationSize variable (TL ca. 1.3 - 1.8 mm); antennae 12

segmented; head and trunk densely punctuated.

DistributionChristmas Island: This species was not collected

during the current survey. In fact,M. pharaonis hasnot been reported from Christmas Island sinceDonisthorpe (1935).

Worldwide: Monomorium pharaonis is native toWest Africa and has been introduced into Asia(including Japan, India and Saudi Arabia),Australia, North, Central and South America,Europe and some islands in the Indian Ocean(including Madagascar) and the Pacific Ocean(including New Zealand and some islands in theHawaiian and Galapagos archipelagoes) (ISSG 2004;McGlynn 1999).

RemarksMonomorium pharaonis frequently nests inside

human structures but rarely displaces native speciesoutside urban environments (Holway et al. 2002;McGlynn 1999). This species is a pest in manyregions of the world. Its presence in hospitals is ofparticular concern as it is a vector for thetransmission of certain human bacterial pathogens(lSSG 2004).

Monomorium cf. subcoecum Emery, 1894

IdentificationVery small (TL ca. 1.1 mm); as part of the

fossolatum-group it is apparently very similar to M.


Figure 53 Records of Monomorillm cf. sllbco/:'cllm onChristmas Island.

australicum (junior synonym M. talpa), which itwas most likely reported as previously fromChristmas Island. Workers of M. cf. subcoecum lackthe domed promesonotum and deeply impressedmetanotal groove found in M. australicum(Heterick 2001). Differs from M. orientale by itsreduced eyes.

DistributionChristmas Island: This cryptic species has only

been found in the traps of the BMP in thenortheastern parts of Christmas Island and in WhipCave (CS) (Figure 53).

Worldwide: This appears to be the same speciesas reported by Heterick (2001) from a seriescollected in Cannon Vale (Queensland).

Genus Pheidole Westwood, 1839Pheidole is one of the world's most diverse ant

genera with many hundreds of species, but thetaxonomy and systematics of this genus in Australiaremain rudimentary (Andersen 2000a). Workers ofPheidole are dimorphic (majors and minors) andmajor workers have very large heads. The genus iseasily identified by the raised pronotum andmesonotum that are much higher than thepropodeum (Figure 19B).

Only P. megacephala and one speciesbelonging to the P. variabilis group were foundduring the current survey. A further species, P.oceanica, has been previously recorded fromChristmas Island. Given the widespreaddistribution of P. variabilis group, it is possiblethat P. oceanica has been misidentified.However, this cannot be verified withoutrecourse to previously collected material.


Plteidole megacepltala (Fabricius, 1793)(Big lieaded Ant, Coastal Brown Ant)

IdentificationTL ca. 3.5 mm (majors), ca. 2.5 mm (minors);

differs from Pheidole sp. (variabjfis) group,amongst other characters, by the smooth and shinytop of the head and pronotum (punctured inPheidole sp. (variabilis group)). Pheidcl/emegacephala is also somewhat larger although sizesmay overlap.

DistributionChristmas Island: Pheidole megacephala is not

common on Christmas Island and appears to bedistributed close to disturbed areas. It isparticularly common around the main settlementarea and in forests adjacent to mine sites and roadsin the Southeast of the Island (Figure 54).

Worldwide: Evidence of the origin of P.megacephala derived from historical humanrecords is scarce (Wheeler 1922), but South Africahas generally been accepted as its native range(Haskins and Haskins 1965; Vanderwoude et al.2000; Wilson and Taylor 1967). This species hasbeen spread to almost all of the more humid partsof the tropics via commerce.

RemarksPheidole megacephala represents one of the most

threatening exotic ant species worldwide and islisted as one of the world's 100 worst invasivespecies (ISSG 2004). In its introduced range, the BigHeaded Ant is a serious threat to biodiversity(Haskins and Haskins 1965; Heterick 1997;Hoffmann et al. 1999; Lieberburg et al. 1975; Majer1985), a pest to agriculture (Bach 1991; Jahn andBeardsley 1994), and a domestic nuisance (Schagen

.... .....

..•.N

AFigure 54 r-(ecords of l'heido/e megacepha/a on

C'hristmas Island.

71

et al. 1994). Although its current distribution onChristmas Island is somewhat limited, this species'preference for shady, humid environments(Greenslade 1972; lIoffman et al. 1999; Majer 1994)suggests that it has the potential to spread acrosslarge portions of Christmas Island's rainforest.

Pheidole sp. (variabilis group)

Nominal speciesPheidole variabilis Mayr, 1876

IdentificationTL ca. 2.8 mm (majors), ca. 1.5 mm (minors);

differs from F'. megacephala by the punctuatedpronotum and top of head, and its smaller size.

DistributionChristmas Island: Pheidole sp. (variabilis group)

is widely distributed across the island, but thisspecies appears to be less common in mine sites(Figure 55).

Worldwide: Based on the collections of the ANIC,this species appears to be a common IndoAustralian representative of Pheidole (Taylor 1990).

RemarksThis species may be the same as the previously

reported P. oceanica (see Pheidole section).

•

N

AFigure 55 Records of Pheido/e sp. (variabi/is gwu p) on

Christmas Island.

Genus Pyramica Roger, 1862

Pyramica membranilera (Emery, 1869)

IdentificationTL ca. 2 mm; body colour yellowish-brown.

Except for a pair of erect scale-like hairs onposterior portion of the head, pilositv almostlacking in this species.

72

BiologyPvramica membranifera is found in the soil of

ratl;er open habitats and is predaceous on a widevariety of small, soft-bodied arthropods (Wilsonand Taylor 1967).

DistributionChristmas Island: The distribution of P.

membranifera on Christmas Island remains obscureas the only record was without precise locality data(Taylor 1990). This species was not recorded duringthe current surveys.

Worldwide: Pvramica membranifera is anaccomplished tra~1p species. It has been recordedwidely from tropical and warm temperate regionsof the world, including Fiji, eastern China, WestIndies and the southeastern US (Wilson and Taylor1967). Brown and Wilson (1959) suggested anAfrican origin, but this was questioned by Bolton(1983).

Genus Solenopsis Westwood, 1840The genus Solenopsis includes two of the most

notorious worldwide invasive species, S. geminata(Fabricius, 1804) (Tropical Fire Ant) and S. invietaBuren, 1972 (Red Imported Fire Ant). Only 5.geminata has been recorded on Christmas Island.However, all identifications of this species shouldbe carefully verified against the diagnosticcharacters of 5. invieta to allow an early detectionof this problematic invasive species. Major workersof both species differ by the vertex of the head infrontal view (geminata: strongly bi-convex, invieta:weakly biconvex), the length of the antennal scapein lateral view (geminata: short, not reaching top ofoccipital margin; invicta: longer, almost reachingthe occipital margin), and the absence (geminata)and possible presence (invieta) of a central clypealtooth.

Solenopsis geminata (Fabricius, 1804)(Tropical Fire Ant)

IdentificationTL ca. 3.0 - 3.5 mm (majors), 2.2 - 2.5 mm

(minors); currently unmistakable on ChristmasIsland: the only species of which the antennal clubconsists of only two segments.

DistributionChristmas Island: On Christmas Island, this

species shows a strong preference for opendisturbed habitats, primarily recorded from minefields and along roads (Figure 56).

Worldwide: 501enopsis geminata is native tosome tropical and temperate regions of the NewWorld (McGlynn 1999; Wilson and Taylor 1967).


Figure 56 Records of SoJenopsis geminata on ChristmasIsland.

Remarks501enopsis geminata is classified as a 'hot climate

specialist' (Anderson 2000b) and, as such, residesonly in hot arid regions. It is therefore unlikely tospread into Christmas Island's forested areas. Thereis evidence that 5. geminata reduces nativeinvertebrate fauna (McGlynn 1999), can have anegative effect on plant life because of itsassociation with honey-dew producing insects (Litand Caasi-Lit 2004), and is a threat to landvertebrates such as lizards and tortoises (Williamsand Whelan 1991). In urban areas it can causechewing damage to PVC coatings of electricalwiring (Prins 1985) and the sting can cause painfulpostules (Schmidt and Hoffmann 1999) with a lowrisk of anaphylactic shock (Collingwood et al. 1997;Hoffmann 1997).

Genus Strumigenys Smith, 1860Species of 5trumigenys are difficult to find other

than when encountered in leaf litter samples(Shattuck 1999). Species in this genus are mostlyspecialised hunters of Collembola and have long,linear mandibles with a few large teeth at the apex.When waiting for prey the mandibles are widelyopened and specialised trigger setae at the ant'smouthparts will initialise the long mandibles tosnap shut with explosive force when prey isencountered. The initial strike itself usually kills theprey, and stinging is not necessary (Deyrup andDeyrup 1999).

Strymigenys emmae (Emery, 1890)

IdentificationVery small (TL ca. 1.2-1.5 mm); differs from 5.


N

AFigure 57 Record of Strumigenys emmac on Christmas

Island.

godeHroyi by the smaller number of antennalsegments (4 instead of 6).

DistributionChristmas Island: This small cryptic species was

only collected in traps of the BMP in theNorthwestern part of the island (Figure 57).IIowever, due to its cryptic behaviour and smallsize it is likely that this species is more widespreadthan reported here.

Worldwide: Stnnnigenys emmae is a pantropicaltramp species known from tropical regionsthroughout the world (Bolton 1983). The geographicorigin of S. emmae is apparently Australia, whereseveral related species occur (Bolton 2(00).However, Africa has also been suggested as itsnative range (Deyrup and Deyrup 1999; Wilson andTaylor 1967)

Strumigenys godeffroyi Mayr, 1866

IdentificationTL ca. 1.2 1.5 mm; differs from S. emmae bv the

number of antennal segments (6 instead of 4)..

DistributionChristmas Island: Onlv one specimen was

collected during the IWS 2005 in the northeasternpart of the island (Figure 58). This species was alsofound in a previous survey lor 1990),suggesting that it is more common than implied bythe IWS 2005. .

Worldwide: Strvmigenys godctfroyi is believedto be native to tropical southeastern' Asia (Wilsonand Taylor 1967). It is widely distributed fromthe Pacific, East Indies, New Cuinea, SolomonIslands tropical mainland of Asia, the

73

N

AFigure 58 Record of Strumigenys godcflroyi on

Christmas Island.

Philippines, and northern Australia and acrossthe Indian Ocean as far as Madagascar (W.L.Brown personal communication in Wilson andTaylor 1967).

Genus Tetramorium Mayr, 1855Members of the genus Tetramorium are fairly

distinctive. The area of the clypeus immediatelybelow the antennal socket is raised into a sharpedged ridge that forms the lower section of the pitaround the base of the antennae (see Shattuck 1999,Figure 584). However, this character is difficult toidentify and therefore not used in this key. Thesurface of the body of the ants is generally deeplysculptured with pits. The front of the head displaysdistinct raised edges (carinae) (except in T. walslll)'Accurate species identification is possible whenapplying the keys of Bolton (1976, 1977).

With eight species present on Christmas Island,Tetramorium is the most speciose genus and onespecies, T. insolens, is particularly abundant.

Tetramorium bicarinatum (NyIander, 1846)

IdentificationTL ca. 2.3 mm. 'I'his species is very similar to T.

insolens, but is distinguished by the sharper frontalangle of the petiole in lateral view (see Figures 20Bvs. 20C), the shorter setae on the head and thedarker gaster (see Bolton 1977 for a detailedidentification table to distinguish both species).

DistributionChristlTlas Island: Tetramorillm bicarinatllm is

mainly found in disturbed habitats such as minesites and near roads (Figure 59).

N

A

74

Figure 59 Records of Tetramorium bicarinatum onChristmas Island.

Worldwide: Tetramorium bicarinatum has beenconsidered native to South-East Asia (Bolton 1977)and Africa (Ingram et a1. 2006), but has been widelydistributed to many parts of the tropics by humancommerce. This species dominates some habitats ofthe New World (Ingram et al. 2006).

Tetramorium insolens (Fr. Smith, 1861)

IdentificationTL ca. 2.3 mm. Very similar to T. bicarinatum, but

distinguished by the less sharp anterior angle of thepetiole in lateral view (Figure 20C vs. 20B), andgenerally lighter gaster and longer setae on the head(see Bolton 1977 for an identification table todistinguish both species).

Figure 60 Records of Tetramorium insoJens onChristmas Island.


DistributionChristmas Island: This species was one of the

most commonly collected ants during the recentsurveys, but appears to be absent from areas on thelower terraces (Figure 60). The widespreaddistribution of T. inso1ens on Christmas Island issomewhat surprising given that it was recorded forthe first time on the island in 1989 (Taylor 1990)(although it may have been confused with T.bicarinatum by Donisthorpe (1935)).

Worldwide: Widespread; Bolton (1977) reportedit from Sri Lanka, Flores, Sulawesi, the Philippines,Solomon Island, New Guinea, Pacific Islands, and ithas been introduced into hot houses in Europe.

Tetramorium lanuginosum Mayr, 1870

IdentificationTL 1.5 - 2.1 mm; within Tetramorium of

Christmas Island most similar to T. wa1shi due tothe presence of bifid or trifid setae, however differsin the darker colour and much less dense pilosity,in particular on the gaster.

DistributionChristmas Island: Widespread and common on

Christmas Island (Figure 61).Worldwide: Probably native to tropical Asia

(Wilson and Taylor 1967) and northern Australia(A. Andersen personal communication), and spreadby commerce to Africa and the Pacific coast ofMexico (Wilson and Taylor 1967).

Figure 61 Records of Tetramorium Januginosum onChristmas Island.

Tetramorium pacificum Mayr, 1870

IdentificationTL ca. 2.0 2.5 mm; easily distinguished from

other Tetramorium on Christmas Island by the


,.

N

A

••

..........

N

AFigure 62 Records of Tetramorium pacificum on

Christmas Island.

uniformly dark brown to blackish-brown colourationand the shape of the petiolar node (Figure 20A).

DistributionChristmas Island: Tetramorium pacificum

appears to be predominantly found on the plateaurainforest (Figure 62).

Worldwide: Tetramorium pacificum is probablynative to the Indo-Australian region, i.e. SoutheastAsia, most of Melanesia, including New Caledonia,Micronesia, Polynesia east to the Marquesas andNorth Queensland (Wilson and Taylor 1967). It isone of the most common ants of the Pacific regionand has probably been introduced to NorthAmerica (Creighton 1950), and some islands,including the Society Islands (Morrison 1996) andNiue (Collingwood 2001).

Figure 63 Records of TelTilmorium simiJlimum onChristmas Island.

1975; Bolton 1977, 1980). It has been spread bycommerce throughout the Americas and theCaribbean, Indian and Pacific Oceans (Bolton 1977,1979, Clark et al. 1982; Wetterer and Wetterer 2004;Wilson and Taylor 1967).

RemarksTetramorium similIimum occurs to about 1lOO m

altitude in dry and mesic habitats in Hawaii (Reimer1994). There, it is limited to disturbed habitats. Thespecies appears to be most active during the morningand evenings (Whitcomb et aI. 1982).

Tetramorium cf. simiIlimum

IdentificationSmall (TL 1.3 - 1.8 mm); see above to distinguish

this species from T. similIimum.

Tetramorium simillimum (Smith, 1851)

IdentificationSmall (TL 1.3 1.8 mm); the short, stout pilosity

on mesonoma easily distinguishes this and T. cf.simijlimum from the other species of Tetramoriumon Christmas Island. In contrast to T. cf.simiIIimum, this ant is uniformly yellow-brown(darker gaster in T. cf. simiIIimum) and the palpformula is 4,3 (2,2 in T·. cl'. simiIIimum).

DistributionChristn1as Island: Tetramorium simillimum is

well dispersed across the island (Figure 63), It is avery small species and may be more common thanindicated by the hand collections of the IWS 2005.

\Vorldwide: Tetramorium similIimum is apantropical tramp species originating from the oldworld tropics (Africa) (Bolton and Collingwood

Figure 64

•

Records of Tetranwrium cf. simiIJimum onChristmas Island.

76

DistributionChristmas Island: This species was found at only

four sites distributed from the northwest to thesoutheast of Christmas Island (Figure 64).

Worldwide: Worldwide distribution unclear(under revision by B. Bolton).

Tetramorium smithi Mayr, 1871

IdentificationTetramorium smithi is the only Tetramorium on

Christmas Island with ll-segmented antennae (allother are 12-segmented).

DistributionChristmas Island: Tetramorium smithi was

encountered at only a few sites during the IWS 2005that are all clustered in the north-east corner of theisland (Figure 65). This distribution potentiallyreflects a recent introduction. All of these sites areadjacent to disturbed habitats such as roads or minesites.

Worldwide: Tetramorium smithi is an IndoMalayan species, reported from Sri Lanka, India,Myanmar, Thailand, Vietnam, Malaya, Borneo andSulawesi (Bolton 1977).

Figure 65 Records of Tetramorium smithi on ChristmasIsland.

Tetramorium walshi Forel, 1890

IdentificationTL ca. 1.5 mm; the very dense pilosity of bifid and

trifid setae distinguishes this species from all otherTetramorium on Christmas Island.

DistributionChristmas Island: Tetramorium walshi was

encountered at only five sites during the IWS 2005,


Figure 66 Records of Tetramorium walshi on ChristmasIsland.

all of which are near roads or at mine sites (Figure66).

Worldwide: Known from India and Thailand(Bolton 1976).

Subfamily Ponerinae Lepeletier, 1835

Genus Anochetus Mayr, 1861

Anochetus sp. (graeffei group)

Nominal speciesAnochetus graeffei Mayr, 1870

IdentificationTL ca. 3.0 mm; distinct shape of head and

mandibles that insert medially on head (Figure 6B);Odontomachus simjJJimum (Figure 6A) has asimilar head and mandible shape, but is nearlythree time as large. The taxonomy of Anochetus sp.(graeffei group) is not resolved and this speciesmust therefore be regarded as representing aspecies group. Brown (1978; p. 587) provided adetailed discussion on A. graeffei systematics: 'Thebounds of graeffei variation, and whether or not thespecies divides into sibling species, are ripe subjectsfor future gamma-taxonomic studies. These studiesare certainly warranted, considering theoutstanding success the species has had as a colonistthrough the Indo-Australian area'.

DistributionChristmas Island: Anochetus sp. (graeffei group)

was found all over the island but only at a limitednumber of sites (Figure 67). However, these arecryptic ants that hunt for prey in the leaf litter andcan be hard to detect unless litter is sifted.


•

•

..

•N

AN

AFigure 67 Records of Anochetus sp. (graeffei grou p) on

Christmas Island.

Worldwide: The nominal species, A. graeHei, isreported to range from Southeast Asia toQueensland (Australia), and eastward intoMicronesia and the Cook Islands (Wilson andTaylor 1967). It is continuously distributedthroughout Melanesia, including New Caledonia.Taxonomic problems, however, make aninterpretation of the distribution of species in thisgroup difficult.

Genus Hypoponera Santschi, 1938

Hypoponera confinis (Roger, 1860)

IdentificationTL ca. 2.2 mm; differs from H. punctatissima in

the relatively longer antennal scapes, and from H.opaciceps by its shiny pronotum and the petiolarnode that narrows dorsaIly (Figure 68).

DistributionChristmas Island: Hypoponera con fin is has been

found over nearly the whole island albeit at only afew sites (Figure 69).

1 mm

Figure 68 Worker of Hvpoponera conf1nis.

Figure 69 Records of Hypoponera confinis onChristmas Island.

Worldwide: Hypoponera confinis is a Widespreadspecies that is probably native throughout India,Ceylon, Indo-China, Indonesia and Melanesia, atleast as far east as New Guinea (Wilson and Taylor1967). Christmas Island may therefore constitutepart of its native range.

Hypoponera opaciceps (Mayr, 1887)

IdentificationDiffers from H. COnflI11 5, the most common

Hypoponera on Christmas Island, by a rectangularshape of the petiolar node in lateral view(narrowing dorsally in H. collfinis), and from H.punctatissima by the longer scape.

DistributionChristmas Island: On Christmas Island, this

species was only reported once withou t preciselocality data (Taylor 1990). It was not found duringany of the recent surveys.

Worldwide: Hypoponera opaciceps is consideredof Brazilian origin and in the New World it reachesmore or less continuouslv from the southern UnitedStates as far south as Montevideo in Uruguay(Wilson and Taylor 1967). It appears to have beenintroduced into the Old World more or lessirregularly by human commerce and was reportedin a number of Polynesian localities, but also thePhilippines and New Caledonia (Wilson and Taylor1967).

Hypoponera punctatissima (Roger, 1859)

IdentificationDiffers from the other two members of


Figure 70 Records of Hypoponera punctatissima onChristmas Island.

Hypoponera on Christmas Island by the shorterantennal scape.

DistributionChristmas Island: One worker was collected by

pitfall trap during the recent cave survey fromDaniel Roux Cave Upper (Cl-56) (Figure 70). Priorto this, a single specimen of H. punctatissima hasbeen reported from Christmas Island withoutprecise locality data (Taylor 1990).

Worldwide: Hypoponera punctatissima isprobably of African origin and has been carriedextensively by man to the warmer parts of the globe(Wilson and Taylor 1967).

RemarksMales of this species are peculiar in that they have

highly worker-like ergatoids, and normal wingedmales have not been found (Wilson and Taylor1967). This behavioural adaptation may havecontributed to this species' success at establishmentwhen introduced into new areas (Taylor 1967).

Genus Leptogenys Roger, 1861

Leptogenys falcigera Roger, 1861

IdentificationTL ca. 6.0 mm; the shape of the mandibles (Figure

11A) unmistakably identify this species onChristmas Island. Species identification is based onthe record of Taylor (1990).

DistributionChristmas Island: Leptogenys falcigera was only

found near the main settlement FIying Fish Cove inthe northeastern part of the island and in the far

Figure 71 Records of Leptogenys falcigera onChristmas Island.

south (Figure 71). It appears to prefer disturbedhabitats.

Worldwide: Leptogenys falcigera is probably ofAfrican origin (Wilson and Taylor 1967).

Leptogenys harmsi Donisthorpe, 1935

IdentificationTL ca 5.5 mm; L. harmsi forms part of the

conigera-group of Leptogenys (Andersen 2000a);the petiole of this species has a distinct shape, withits rear face distinctly higher than the frontal face(Figures 12B vs. 12A, 72). We attributed L. peuquetias reported by Collingwood and Hedlund (1980) tothis species, as it also forms part of the conigeragroup. Pending further revisionary work, we mustalso consider the earlier report of the similar L.diminuta (Smith, 1857) as misidentification of thecommon L. harmsi, as we can assume thatDonisthorpe (1935) was aware of the earlieridentification of this species as L. diminuta by Kirby(1888, 1900) (see Table 1).

DistributionChristmas Island: Leptogenys harmsi is

predominantly found on the eastern parts of the

Figure 72 Worker of Leptogenys harmsi.


•.N

A

••••'.....•

•

..-,.,..~....

Figure 73 Records of Leptogenys harmsi on ChristmasIsland.

island and is common near disturbed areas androads (Figure 73).

Worldwide: Originally described from ChristmasIsland. Based on the ANIC collection it iswidespread in the Indonesian area and possibly ajunior synonym (Taylor 1990).

Genus Odontomachus Latreille, 1804

Odontomachus simillimus F. Smith, 1858

IdentificationSimilar head and mandibles as Anochetlls sp.

(graeffei group), but much larger (Tt ca. 8.0 mm)and with a petiolar node that ends in a dorsal thorn(Figure 74).

DistributionChristmas Island: Odontomachlls simiIJimlls was

recorded from Christmas Island as early as 1915(Table 1). This is a large and conspicuous speciesthat is easily collected. It is widespread andcommon on the island (Figure 75), but generallyabsent in mine sites.

Figure 74 Worker of Odontomachlls simillimlls.

Figure 75 Records of Odontomaclws simillimlls onChristmas Island.

Worldwide: Odontomachlls simiJIimlls rangescontinuously from Ceylon to Micronesia andinner Polynesia. Within this range it is one of thedominant ants, maintaining dense populations ina wide variety of habitats (WiIson and Taylor1967).

RemarksThere is no doubt that the early records of 0.

haematodes from Christmas Island representmisidentified 0. simil/imlls (see Table 1). Thesimilarity of these species is indicated by thedescription of a new subspecies of 0. haematodesfrom Christmas Island, O. haematodes var.breviceps, which was subsequently synonymisedwith 0. simiIJimlls (Table 1).

Genus Pachycondyla Smith, 1858

Subgenus Brachyponera Emery, 1900

Pachycondyla (Brachyponera) christmasi(Donisthorpe, 1935)

IdentificationTt ca. 3.0 mm; two spines on the tibia of the third

leg, well-developed eyes (Figure 76) (in contrast toFachycondyla (Trachymesopus) darwinii; Figure78) and no teeth on the inner margin of the claws ofthe third leg (in contrast to Leptogenys).

DistributionChristmas Island: Fachycondvla (Brachvponera)

christmasi is Widespread on the plateau with theexclusion of mine sites. It is less common on theterraces of Christmas Island (Figure 77).

Worldwide: Appears to be a common species inthe Indo-Australian region based on collections ofthe ANIC (Iaylor 1990).

80

Figure 76 Worker of Pachycondyla (Brachyponera)christmasi.

Figure 77 Records of PachycondyJa (Brachyponera)christmasi on Christmas Island.

RemarksPachycondyla (Brachyponera) christmasi was

originally described from Christmas Island, but itappears to be widespread in the Indonesian areabased on the ANIC ant collection; a senior synonymmay exist (Taylor 1990). Collingwood and Hedlund(1980) suggested it to be a junior synonym ofPachycondyla solitaria. We could not confirm thissynonymy, as we did not have access to material ofP. solitaria. Hence, we list this abundant speciesfrom Christmas Island as P. (B.) christmasi pendinga revision of the genus.

Subgenus Trachymesopus Emery, 1911

Pachycondyla (Trachymesopus) darwinii (Forel,1893)

IdentificationTL ca. 2.0 mm; the presence of two spines on the

third tibia (one pectinate spine in the similarHypoponera) in combination with the very smalleyes (Figure 78) identifies this species within the


Figure 78 Worker of Pachycondyla (Trachymesopus)darwinii.

Ponerinae of Christmas Island. The identification ofthis species remains tentative since the workersreported here are unusually larger than queens incollections (A. Andersen personal communication).

DistributionChristmas Island: This species was reported by

Taylor (1990) based on a single queen withoutdetailed locality data. The only recent record isfrom 19th Hole Cave collected during a cave surveyin April 2004 (WAM, registration no. BES13582)(Figure 79).

Worldwide: This species is widespread in theIndo-Australian region (Taylor 1990).

RemarksThe record of two workers of this species from

caves on Christmas Island suggests troglobiticbehaviour. This may also explain why this speciesis mainly known from females collected at lights(A. Andersen personal communication).

Figure 79 Records of PachycondyJa (Trachymesopus)darwinii on Christmas Island.


8~o~~-A\

..

.. f...•• /· ?~~~ 1mm.

~ftFigure 80 Worker of Platythyrea sp. (paraIIda group).

Genus Platythyrea Roger, 1863

Platythyrea sp. (parallela group)

Nominal speciesPlatythyrea parallela (Smith, 1859)

IdentificationTl ca. 2.5 - 3.0 mm; uniformly brown; the long,

almost cylindrical shape of the petiole identifies thisspecies in comparison to all other Ponerinae fromChristmas Island (Figure 80). The taxonomy of thespecies in this group is not resolved and therefore itis listed here as a species group (A. Andersenpersonal communication).

DistributionChristmas Island: Although workers of

Platythyrea sp. (parallela group) are conspicuous,some species of this group are known to foragearboreally (A. Andersen personal communication),rendering them potentially difficult to collect byhand. As such, the current distribution ofPlatythyrea sp. (parallela group) as illustrated in

. ..

N

/\

81

Figure 81 may not fully represent the distributionof this species across Ihe island.

Worldwide: The nominal species, P/atythyreaparallela, is considered native to Australia (Shattuckand Bennett 2001). It is also found from tropicalAsia to Samoa (Wilson and Taylor 19(7) and Fiji(Ward and Wetterer 2006).

Genus Ponera latreilIe, 1804

Ponera swezeyi (Wheeler, 1933)

IdentificationThe smallest ponerine ant on Christmas Island

(TL. ca. 1.7 mm, I1W 0.30 0.32 mm); the presenceof a translucent spot on the underside of the petiole(fenestra) undoubtedly identifies this species.Accurate species identification is possible with akey in a detailed revision of Ponera (Taylor 1967).

DistributionChristmas Island: This species was collected at

only four sites; two waypoints in the IWS 2005, atGrants Well Cave (CS) and at the BMP survey site(Figure 82)

Worldwide: This species was thought to beendemic to Hawaii until it was discovered onSamoa (Wilson and Taylor 1967). The native rangeof P. swezevi is thought to be South-East Asia(Taylor 1990).

RemarksThis species' predilection to soil nesting rather

than rotting logs (as is usual in Ponera) may haveincreased the likelihood of its dispersal by man(Wilson and Taylor 19(7).

•,

N

/\Figure 81 I\ecords of Platvthvrea sp. (parallela group)

on Christmas Island.Figure 82 Record S 01 Ponera

Island.011 Christmas

82

ACKNOWLEDGEMENTS

We are grateful to the following individuals forexpert advice on ant identification, ecology anddistribution for the indicated genera: AlanAndersen (CSIRO Darwin; variable species), ArchieMacarthur (South Australian Museum, Adelaide;Camponotus), Barry Bolton (Isle of Wight;Tetramorium and Technomyrmex), Brian Heterick(Curtin University of Technology, Perth;Monomorium) and John LaPolla (SmithsonianInstitute, Washington; Paratrechina). DennisO'Dowd (Monash University, Melbourne) providedinformation on recent collections of A.zwaJuwenburgi. We thank Alan Anderson, BrianHeterick and Jonathan Mayer for helpful commentson earlier versions of this manuscript. LaurenBarrow (PANCI) provided helpful feedback on theuse of this key.

Any new key to ants, in particular on subfamilyand generic level, will unavoidably containelements of previously published keys. Of greathelp to establish useful diagnostic characters at thesubfamily and generic level were Shattuck (1999),Wilson and Taylor (1967), Bolton (1999), Andersen(2000a), Reimer (unpublished) and Ward (2005).

Special thanks to the following PANCI Staff whospent many hours trampling through the forest tocollect ants during the IWS 2005: Haddis Alpisal,Nicolas Chapellon, Claire Davies, Gary Foo, DavidJames, John Jaycock, Mick Jeffreys, Ruth Man, ImranPereira and Kent Retallick. Bill Humphreys (WesternAustralian Museum) and Tim Moulds (SouthAustralian Museum) made their ant collections fromChristmas Island available for study.

This work was funded by Parks Australia North,Christmas Island. VWF received funding throughthe Australian Biological Resources Study (ABRS)for a revision of the orb-weaving spiders(Araneidae) of Australia while this paper waswritten up.

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Malll/script received 25 October 2007; accepted 11 March2008.

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