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Pupal Dimensions as Predictors of Adult Size in Fitness Studiesof Aedes aegypti (Diptera Culicidae)Author(s) C J M KoenraadtSource Journal of Medical Entomology 45(2)331-336 2008Published By Entomological Society of AmericaDOI httpdxdoiorg1016030022-2585(2008)45[331PDAPOA]20CO2URL httpwwwbiooneorgdoifull1016030022-258528200829455B3313APDAPOA5D20CO3B2

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SHORT COMMUNICATIONS

Pupal Dimensions as Predictors of Adult Size in Fitness Studies ofAedes aegypti (Diptera Culicidae)

CJM KOENRAADT1

Department of Entomology Cornell University 3131 Comstock Hall Ithaca NY 14853

J Med Entomol 45(2) 331ETH336 (2008)

ABSTRACT Adult body size is a central life history character in mosquito THORNtness studies I evaluatedthe predictive values of pupal cephalothorax length cephalothorax width and wet weight for adultsize (wing length) of male and female Aedes aegypti (L) (Diptera Culicidae) Cephalothorax lengthwas the most consistent and accurate predictor of adult size Width of the cephalothorax and wetweight were more variable and they signiTHORNcantly decreased shortly before adult emergence I proposethat cephalothorax length could be used as a proxy for adult size to test how physical and biologicalfactors such as resource-limited environments and competition affect mosquito THORNtness with theadvantage that the specimen does not need to be killed

KEY WORDS Aedes aegypti THORNtness cephalothorax length cephalothorax width wet weight

Measuring THORNtness traits of mosquito populations isimportant to understand their role in disease trans-mission Such studies address the effects of competi-tion density dependence local adaptation (eg in thecase of introduced species) and blood-feeding be-havior on factors such as population growth (Livdahland Sugihara 1984) and vector competence (Paulsonand Hawley 1991 Scott et al 1997) With the designof mosquito strains refractory to various vector-bornepathogens and the advancement of molecular tools forthe improvement of sterile insect technique (SIT)programs there has been a renewed interest in theconcept of mosquito THORNtness (Charlwood 2003 Scott etal 2006) It is likely that a large variety of geneticallymodiTHORNed mosquito strains will be developed for vec-tors such as Aedes aegypti (L) and Anopheles gambiaess Giles (Diptera Culicidae) Strains will be made upof different antipathogen effector genes markergenes and drive mechanisms (James 2005) Thesecandidate strains require simple and rapid evaluationsof their THORNtness Ideally those that are potentially suc-cessful for disease control are moved forward fromtests in the laboratory to evaluations under semiTHORNeldand THORNeld conditions as rapidly as possible but lessonsfrom genetic control trials in the past have shown thatscrutiny at all of these steps is required (Lounibos2003 Reisen 2003)

Because THORNtness is a dynamic and complex conceptit is important to pin down the major determinants ofTHORNtness to prioritize research efforts There are twostages in the life of a mosquito where direct compe-tition will occur and where relative THORNtness will deter-mine the outcome of this competition the mating

arena and the larval habitat Earlier research hasshown that adult body size is a central life historycharacter underlying mosquito THORNtness Body size is adirect result of density and nutritional conditions inthe larval habitat (Hawley 1985 Lyimo et al 1992Lounibos et al 1993) In adult females body size islinked with fecundity survival bloodmeal size andblood-feeding success and feeding frequency (Stein-wascher 1982 Haramis 1983 Nasci 1986 1987 Packerand Corbet 1989 Briegel 1990 Lyimo and Takken1993 Renshaw et al 1994 Blackmore and Lord 2000)but also susceptibility to pathogen infection (Taka-hashi 1976 Baqar et al 1980 Grimstad and Haramis1984 Paulson and Hawley 1991) Male size affectssurvival (Reisen et al 1984) and sperm capacity (Pon-lawat and Harrington 2007)

An important question for mosquito THORNtness studiesis how aquatic resource-limited environments in theTHORNeld affect the outcome of competition in terms ofsurvival developmental rate and body size The latterthree components determine the per capita growthrate of populations (Livdahl and Sugihara 1984Livdahl 1984) Traditionally adult body size is measuredas wing length or dry weight and both are highlycorrelated (Nasci 1990 Siegel et al 1992) From alogistical standpoint transferring pupae to emergencecontainers and either drying and weighing emergedfemales or mounting wings can be time-consumingFurthermore this method requires destruction of thespecimen Pupal size could be used for a variety ofapplications where advanced knowledge of adult bodysize is required I therefore examined the accuracy ofpupal dimensions as predictors of adult size Pupalcephalothorax length cephalothorax width and wet1 Corresponding author e-mail cjk48cornelledu

0022-2585080331ETH0336$04000 2008 Entomological Society of America

mass were investigated as predictors of adult size inAeaegypti

Materials and Methods

Mosquitoes Ae aegypti pupae and adults were sec-ond generation offspring of a strain established withTHORNeld-collected pupae from Tapachula Mexico (14 54N 92 15 W) The strain was maintained in an envi-ronmental chamber set at 27C 80 RH and a pho-toperiod of 1212 (LD) h Within 4 h of hatching THORNrstinstars were reared at the following fooddensity com-binations to obtain different-sized pupae and adults1) four larvae per 5 ml 17 mg of food per larva 2)four larvae per 5 ml 085 mg of food per larva and(3) one larva per 5 ml 23 mg of food per larva Foodconsisted of a 11 mixture of BrewerOtildes yeast and lact-albuminMeasurements After chilling individual pupae for

25 min at 20C cephalothorax width was measuredas the widest part of the cephalothorax when viewedfrom its dorsal side (Fig 1A) Pupae remained uprightby holding them in the smallest drop of water possible(just before the pupa tipped to its lateral side) Thedistance generally overlaid the pupal halter sheathsand metanotal plate (Knight 1971) After moving thepupa to its lateral side cephalothorax length was mea-sured as the distance between the anterior point of themedian keel and the ventral tip of the pupal wingsheath (Knight 1971) (Fig 1B) Pupae were thenblotted dry and weighed to the nearest 01 mg on anelectronic balance (AB204-SFACT Mettler ToledoColumbus OH) Pupae were reared to adults in plastictubes (12 by 100 cm) containing 2ETH3 ml of tap waterAdults were killed and one wing was removed andmounted on a slide Then the wing length was mea-sured to the nearest 01 mm from the axial incision tothe wing tip excluding the fringe scales Pupae werealways measured when they were 24 h old Mea-

surements were obtained for 54 males and 43 femalesCephalothorax length width and pupal wet weightwere regressed against adult size and predictive val-ues were evaluated by their coefTHORNcients of determi-nation (R2 values) Differences between males andfemales in slope and intercept of regression equationswere evaluated with StudentOtildes t-tests (SPSS 140 SPSSInc Chicago IL)

To conTHORNrm whether pupal dimensions are constantthrough the pupal stage 26 female pupae and 20 malepupae were randomly selected and measured 2 h ofpupation 22ETH26 h after pupation and 44ETH48 h afterpupation At 27C the average time spent in the pupalstage is 48 h (Christophers 1960) Therefore the THORNnalmeasurements were done shortly before emergenceof the adult Only adults that emerged successfullyafter obtaining the three measurements were includedin the analysis Proportional changes in pupal dimen-sions after 22ETH26 and 44ETH48 h were calculated com-pared with their dimensions at the THORNrst measurement(2 h)

Finally repeatability was calculated by measuringand remeasuring 25 male and 25 female pupae within1 h (Lessels and Boag 1987) Remeasurements weremade with no knowledge of previous measurementvalues

Results

Cephalothorax length was the best predictor ofadult wing length for both males and females (iehighest R2 values Fig 2) R2 values of the three pre-dictors were always higher for females than for malesSlope and intercept of the cephalothorax length re-gression line were not statistically different betweenmales and females A signiTHORNcant difference in slopebetween males and females was found for cephalo-thorax width (t 2509P 0014) and in intercept forpupal wet weight (t 2905 P 0005) These results

Fig 1 Male Ae aegypti pupa (A) Dorsal view arrow indicates cephalothorax width (B) Lateral view arrow indicatescephalothorax length

332 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

y = 1110x + 0014R2 = 0904

y = 0974x + 0119R2 = 0656

14

16

18

20

22

24

26

28

30

14 16 18 20 22 24 26Cephalothorax length (mm)

Females

Males

y = 1942x + 0119R2 = 0882

y = 1419x + 0490R2 = 0554

14

16

18

20

22

24

26

28

30

08 09 10 11 12 13 14Cephalothorax width (mm)

Females

Males

Adu

lt w

ing

leng

th (m

m)

b

y = 0296x + 1560R2 = 0842

y = 0351x + 1280R2 = 0552

14

16

18

20

22

24

26

28

30

08 12 16 20 24 28 32 36 40

Pupal wet weight (mg)

Females

Males

c

a

Fig 2 Relationships between (a) pupalcephalothorax length (millimeters) and adultwing length (millimeters) (b) pupal cepha-lothorax width (millimeters) and adult winglength (millimeters) and (c) pupal wetweight (milligrams) and adult wing lengthRegression equations for males and femalesand their corresponding R2 values are indi-cated in the THORNgures

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 333

indicate that regression lines of males and femaleswere similar for cephalothorax length but not forcephalothorax width and pupal wet weight

Within 1 d after pupation no signiTHORNcant changesin cephalothorax length width or pupal wet weightwere detected (Fig 3) However shortly beforeemergence of the pupa both cephalothorax width andwet weight signiTHORNcantly decreased for both males andfemales (95 conTHORNdence intervals do not include ldquo0rdquo)whereas cephalothorax length remained the sameRelative weight loss of males was higher than of fe-males but not signiTHORNcantly so (t 1898 P 0065)

Repeatabilityvaluesofcephalothorax lengthwidthand pupal wet weight were 0815 0772 and 0735 formales and 0914 0859 and 0933 for females respec-tively These results indicate that measurements wereless consistent for males than for females for all three

predictors Although pupal wet weight had the highestrepeatability for females it was the lowest of the threefor males For males and females taken togethercephalothorax length measurements were most con-sistent (ie high repeatability values)

Discussion

I conclude that cephalothorax length provides thebest estimator of adult wing length This parameterhad the best model THORNt was highly repeatable and didnot change through the pupal stage I expected thismorphometric measurement to correlate the best be-cause it overlaps the pupal wing sheath Cephalotho-rax width and wet weight were more variable lessrepeatable and even signiTHORNcantly decreased shortlybefore emergence particularly the weight of the pupa

Female Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

Male Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

a

b

Fig 3 Proportional changes in cephalothorax length cephalothorax width and wet weight for (a) 20 male and (b) 26female Ae aegypti pupae relative to sizeweight within 2 h of pupation P 005

334 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

The change in shape and loss of weight may be relatedto preparations for emergence in which the imago willpush its way out probably spending much energy andlosing weight as a result Several pupae were ready toemerge at the third time measurement (44ETH48 h)because air had entered the cavity between thepharate imago and the pupal skin (Christophers 1960)

Steinwascher (1982) reported signiTHORNcant correla-tions between pupal and adult mass of Ae aegypti andalso found these relations to be stronger for femalesthan for males (r 098 for females and r 057 formales) In our study Pearson correlation coefTHORNcientswould be 092 and 074 for the correlation betweenpupal weight and adult wing length of females andmales respectively and 095 and 081 for the correla-tion between cephalothorax length and adult winglength of females and males respectively Thus theobservation that for a given pupal size male size ismore variable than female size in both our study andthat of Steinwascher (1982) suggests that this may bean inherent characteristic of male biology Final winglength has been demonstrated to depend on temper-ature shortly after emergence (van den Heuvel 1963)but conditions for our experiments were equal for allemerging adults

For Ae albopictus females strong correlations be-tween female pupal wet weight and adult wing length(R2 089) were found (Blackmore and Lord 2000)comparable with our cephalothorax length versusadult size relationship (R2 090) Armbruster andHutchinson (2002) concluded that pupal mass couldbe used reliably to predict fecundity of Ae albopictusand Ae geniculatus Our study indicates pupal mass isless desirable for predicting adult size because of itsmore variable nature A statistical analysis of severalpublished studies on the relationship between adultwing length and body weight concluded that mea-surement error is more likely with body weight (Siegelet al 1992) In addition wing length is a THORNxed char-acter whereas weight of adults may be confounded byfactors such as feeding history and gravid status (vanden Heuvel 1963 Siegel et al 1992) Because of thesedrawbacks adult dry weight was not considered incurrent study

Future studies that evaluate mosquito THORNtness (egcomparisons of transgenic and wild-type strains)could screen initially for effects by measuring pupalcephalothorax length If no differences are found it isless likely that physiological THORNtness effects in the adultstage are detected because adults of similar size areunlikely to differ in fecundity survival and blood-feeding frequency If differences in pupal size arefound this could initiate further studies into howthese differences affect THORNtness in later life Such ex-periments could be continued with the same individ-uals because samples do not need to be destroyedwhen measuring cephalothorax length I stress thatassessment of size differences are only part of theequation Additional studies should investigate behav-ioral THORNtness differences between strains (mating hostseeking and oviposition) because they could differeven if body sizes are equal

Acknowledgments

I thank Kaitlyn Van Arsdell for technical help during therearing and measurement procedures Laura Harrington isacknowledged for support and advice during the study Thiswork was funded in part by a grant to the Regents of theUniversity of California from the Foundation for the NationalInstitutes of Health through the Grand Challenges in GlobalHealth initiative and Hatch Project NYC-139432

References Cited

Armbruster P andRAHutchinson 2002 Pupal mass andwing length as indicators of fecundity in Aedes albopictusand Aedes geniculatus (Diptera Culicidae) J Med En-tomol 39 699ETH704

Baqar S C G Hayes and T Ahmed 1980 The effect oflarval rearing conditions and adult age on the suscepti-bility of Culex tritaeniorhynchus to infection with WestNile Virus Mosq News 40 165ETH171

Blackmore M S and C C Lord 2000 The relationshipbetween size and fecundity in Aedes albopictus J VectorEcol 25 212ETH217

Briegel H 1990 Metabolic relationship between femalebody size reserves and fecundity of Aedes aegypti J In-sect Physiol 36 165ETH172

Charlwood J D 2003 May the force be with you measur-ing mosquito THORNtness in the THORNeld pp 243 InW Takken andT W Scott [eds] Ecological aspects for application ofgenetically modiTHORNed mosquitoes Kluwer Academic Pub-lishers Dordrecht The Netherlands

Christophers S K 1960 Aedes aegypti (L)ETHthe yellow fe-ver mosquito Cambridge University Press LondonUnited Kingdom

Grimstad P R and L D Haramis 1984 Aedes triseriatus(Diptera Culicidae) and La Crosse virus III Enhancedoral transmission by nutrition deprived mosquitoesJ Med Entomol 21 249ETH256

Haramis L D 1983 Increased adult size correlated withparity in Aedes triseriatus Mosq News 43 77ETH79

Hawley W A 1985 The effect of larval density on adultlongevity of a mosquito Aedes sierrensis epidemiologicalconsequences J Anim Ecol 54 955ETH964

James A A 2005 Gene drive systems in mosquitoes rulesof the road Trends Parasitol 21 64ETH67

Knight K L 1971 A mosquito taxonomic glossary VII Thepupa Mosq Syst Newsl 3 42ETH65

Lessels C M and P T Boag 1987 Unrepeatable repeat-abilities a common mistake Auk 104 116ETH121

Livdahl T P 1984 InterspeciTHORNc interactions and the r-KcontinuumETHlaboratory comparisons of geographic strainsof Aedes triseriatus Oikos 42 193ETH202

Livdahl T P and G Sugihara 1984 Non-linear interac-tions of populations and the importance of estimatingper-capita rates of change J Anim Ecol 53 573ETH580

Lounibos L P 2003 Genetic control trials and the ecologyofAedes aegypti at the Kenya coast pp 243 InW Takkenand T W Scott [eds] Ecological aspects for applicationof genetically modiTHORNed mosquitoes Kluwer AcademicPublishers Dordrecht The Netherlands

Lounibos L P N Nishimura and R L Escher 1993 Fit-ness of a treehole mosquitoETHinszliguences of food type andpredation Oikos 66 114ETH118

Lyimo E O and W Takken 1993 Effects of adult bodysize on fecundity and the pregravid rate of Anophelesgambiae females in Tanzania Med Vet Entomol 7 328ETH332

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 335

Lyimo E O W Takken and J C Koella 1992 Effect ofrearing temperature and larval density on larval survivalage at pupation and adult size of Anopheles gambiaeEntomol Exp Appl 63 265ETH271

Nasci R S 1986 The size of emerging and host-seekingAedes aegypti and the relation of size to blood-feedingsuccess in the THORNeld J Am Mosq Control Assoc 2 61ETH62

Nasci R S 1987 Adult body size and parity in THORNeld popu-lations of the mosquitoes Anopheles crucians Aedes tae-niorhynchus and Aedes sollicitans J Am Mosq ControlAssoc 3 636ETH637

Nasci R S 1990 Relationship of wing length to adult dry-weight in several mosquito species (Diptera Culicidae)J Med Entomol 27 716ETH719

Packer M J and P S Corbet 1989 Size variation andreproductive success of female Aedes punctor (DipteraCulicidae) Ecol Entomol 14 297ETH309

Paulson S L and W A Hawley 1991 Effect of body sizeon the vector competence of THORNeld and laboratory popu-lations of Aedes triseriatus for La Crosse Virus J AmMosq Control Assoc 7 170ETH175

Ponlawat A andLCHarrington 2007 Age and body sizeinszliguence male sperm capacity of the dengue vectorAedesaegypti (Diptera Culicidae) J Med Entomol 44 422ETH426

Reisen W K 2003 Lessons from the past an overview ofstudies by the University of Maryland and the Universityof California Berkeley pp 243 InW Takken and T WScott [eds] Ecological aspects for application of genet-ically modiTHORNed mosquitoes Kluwer Academic PublishersDordrecht The Netherlands

Reisen W K M M Milby and M E Bock 1984 Theeffects of immature stress on selected events in the lifehistory of Culex tarsalis Mosq News 44 385ETH395

Renshaw M M W Service and M H Birley 1994 Sizevariation and reproductive success in the mosquitoAedescantans Med Vet Entomol 8179ETH186

Scott TW A Naksathit J F Day P Kittayapong and J DEdman 1997 A THORNtness advantage for Aedes aegypti andthe viruses it transmits when females feed only on humanblood Am J Trop Med Hyg 57 235ETH239

Scott TW J LRasgonWCBlack IV andFGould 2006Fitness studies developing a consensus methodology pp210 In BGJ Knols and C Louis [eds] Bridging labo-ratory and THORNeld research for genetic control of diseasevectors Kluwer Academic Publishers Dordrecht TheNetherlands

Siegel J P R J Novak R L Lampman and B A Steinly1992 Statistical appraisal of the weight-wing length re-lationship of mosquitoes J Med Entomol 29 711ETH714

Steinwascher K 1982 Relationship between pupal massand adult survivorship and fecundity for Aedes aegyptiEnviron Entomol 11150ETH153

TakahashiM 1976 The effects of environmental and phys-iological conditions ofCulex tritaeniorhynchus on patternof transmission of Japanese encephalitis virus J MedEntomol 13 275ETH284

van den Heuvel M J 1963 The effect of rearing temper-ature on the wing length thorax length leg length andovariole number of the adult mosquito Aedes aegypti(L) Trans R Entomol Soc Lond 115 197ETH216

Received 25 September 2007 accepted 7 December 2007

336 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

mass were investigated as predictors of adult size inAeaegypti

Materials and Methods

Mosquitoes Ae aegypti pupae and adults were sec-ond generation offspring of a strain established withTHORNeld-collected pupae from Tapachula Mexico (14 54N 92 15 W) The strain was maintained in an envi-ronmental chamber set at 27C 80 RH and a pho-toperiod of 1212 (LD) h Within 4 h of hatching THORNrstinstars were reared at the following fooddensity com-binations to obtain different-sized pupae and adults1) four larvae per 5 ml 17 mg of food per larva 2)four larvae per 5 ml 085 mg of food per larva and(3) one larva per 5 ml 23 mg of food per larva Foodconsisted of a 11 mixture of BrewerOtildes yeast and lact-albuminMeasurements After chilling individual pupae for

25 min at 20C cephalothorax width was measuredas the widest part of the cephalothorax when viewedfrom its dorsal side (Fig 1A) Pupae remained uprightby holding them in the smallest drop of water possible(just before the pupa tipped to its lateral side) Thedistance generally overlaid the pupal halter sheathsand metanotal plate (Knight 1971) After moving thepupa to its lateral side cephalothorax length was mea-sured as the distance between the anterior point of themedian keel and the ventral tip of the pupal wingsheath (Knight 1971) (Fig 1B) Pupae were thenblotted dry and weighed to the nearest 01 mg on anelectronic balance (AB204-SFACT Mettler ToledoColumbus OH) Pupae were reared to adults in plastictubes (12 by 100 cm) containing 2ETH3 ml of tap waterAdults were killed and one wing was removed andmounted on a slide Then the wing length was mea-sured to the nearest 01 mm from the axial incision tothe wing tip excluding the fringe scales Pupae werealways measured when they were 24 h old Mea-

surements were obtained for 54 males and 43 femalesCephalothorax length width and pupal wet weightwere regressed against adult size and predictive val-ues were evaluated by their coefTHORNcients of determi-nation (R2 values) Differences between males andfemales in slope and intercept of regression equationswere evaluated with StudentOtildes t-tests (SPSS 140 SPSSInc Chicago IL)

To conTHORNrm whether pupal dimensions are constantthrough the pupal stage 26 female pupae and 20 malepupae were randomly selected and measured 2 h ofpupation 22ETH26 h after pupation and 44ETH48 h afterpupation At 27C the average time spent in the pupalstage is 48 h (Christophers 1960) Therefore the THORNnalmeasurements were done shortly before emergenceof the adult Only adults that emerged successfullyafter obtaining the three measurements were includedin the analysis Proportional changes in pupal dimen-sions after 22ETH26 and 44ETH48 h were calculated com-pared with their dimensions at the THORNrst measurement(2 h)

Finally repeatability was calculated by measuringand remeasuring 25 male and 25 female pupae within1 h (Lessels and Boag 1987) Remeasurements weremade with no knowledge of previous measurementvalues

Results

Cephalothorax length was the best predictor ofadult wing length for both males and females (iehighest R2 values Fig 2) R2 values of the three pre-dictors were always higher for females than for malesSlope and intercept of the cephalothorax length re-gression line were not statistically different betweenmales and females A signiTHORNcant difference in slopebetween males and females was found for cephalo-thorax width (t 2509P 0014) and in intercept forpupal wet weight (t 2905 P 0005) These results

Fig 1 Male Ae aegypti pupa (A) Dorsal view arrow indicates cephalothorax width (B) Lateral view arrow indicatescephalothorax length

332 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

y = 1110x + 0014R2 = 0904

y = 0974x + 0119R2 = 0656

14

16

18

20

22

24

26

28

30

14 16 18 20 22 24 26Cephalothorax length (mm)

Females

Males

y = 1942x + 0119R2 = 0882

y = 1419x + 0490R2 = 0554

14

16

18

20

22

24

26

28

30

08 09 10 11 12 13 14Cephalothorax width (mm)

Females

Males

Adu

lt w

ing

leng

th (m

m)

b

y = 0296x + 1560R2 = 0842

y = 0351x + 1280R2 = 0552

14

16

18

20

22

24

26

28

30

08 12 16 20 24 28 32 36 40

Pupal wet weight (mg)

Females

Males

c

a

Fig 2 Relationships between (a) pupalcephalothorax length (millimeters) and adultwing length (millimeters) (b) pupal cepha-lothorax width (millimeters) and adult winglength (millimeters) and (c) pupal wetweight (milligrams) and adult wing lengthRegression equations for males and femalesand their corresponding R2 values are indi-cated in the THORNgures

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 333

indicate that regression lines of males and femaleswere similar for cephalothorax length but not forcephalothorax width and pupal wet weight

Within 1 d after pupation no signiTHORNcant changesin cephalothorax length width or pupal wet weightwere detected (Fig 3) However shortly beforeemergence of the pupa both cephalothorax width andwet weight signiTHORNcantly decreased for both males andfemales (95 conTHORNdence intervals do not include ldquo0rdquo)whereas cephalothorax length remained the sameRelative weight loss of males was higher than of fe-males but not signiTHORNcantly so (t 1898 P 0065)

Repeatabilityvaluesofcephalothorax lengthwidthand pupal wet weight were 0815 0772 and 0735 formales and 0914 0859 and 0933 for females respec-tively These results indicate that measurements wereless consistent for males than for females for all three

predictors Although pupal wet weight had the highestrepeatability for females it was the lowest of the threefor males For males and females taken togethercephalothorax length measurements were most con-sistent (ie high repeatability values)

Discussion

I conclude that cephalothorax length provides thebest estimator of adult wing length This parameterhad the best model THORNt was highly repeatable and didnot change through the pupal stage I expected thismorphometric measurement to correlate the best be-cause it overlaps the pupal wing sheath Cephalotho-rax width and wet weight were more variable lessrepeatable and even signiTHORNcantly decreased shortlybefore emergence particularly the weight of the pupa

Female Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

Male Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

a

b

Fig 3 Proportional changes in cephalothorax length cephalothorax width and wet weight for (a) 20 male and (b) 26female Ae aegypti pupae relative to sizeweight within 2 h of pupation P 005

334 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

The change in shape and loss of weight may be relatedto preparations for emergence in which the imago willpush its way out probably spending much energy andlosing weight as a result Several pupae were ready toemerge at the third time measurement (44ETH48 h)because air had entered the cavity between thepharate imago and the pupal skin (Christophers 1960)

Steinwascher (1982) reported signiTHORNcant correla-tions between pupal and adult mass of Ae aegypti andalso found these relations to be stronger for femalesthan for males (r 098 for females and r 057 formales) In our study Pearson correlation coefTHORNcientswould be 092 and 074 for the correlation betweenpupal weight and adult wing length of females andmales respectively and 095 and 081 for the correla-tion between cephalothorax length and adult winglength of females and males respectively Thus theobservation that for a given pupal size male size ismore variable than female size in both our study andthat of Steinwascher (1982) suggests that this may bean inherent characteristic of male biology Final winglength has been demonstrated to depend on temper-ature shortly after emergence (van den Heuvel 1963)but conditions for our experiments were equal for allemerging adults

For Ae albopictus females strong correlations be-tween female pupal wet weight and adult wing length(R2 089) were found (Blackmore and Lord 2000)comparable with our cephalothorax length versusadult size relationship (R2 090) Armbruster andHutchinson (2002) concluded that pupal mass couldbe used reliably to predict fecundity of Ae albopictusand Ae geniculatus Our study indicates pupal mass isless desirable for predicting adult size because of itsmore variable nature A statistical analysis of severalpublished studies on the relationship between adultwing length and body weight concluded that mea-surement error is more likely with body weight (Siegelet al 1992) In addition wing length is a THORNxed char-acter whereas weight of adults may be confounded byfactors such as feeding history and gravid status (vanden Heuvel 1963 Siegel et al 1992) Because of thesedrawbacks adult dry weight was not considered incurrent study

Future studies that evaluate mosquito THORNtness (egcomparisons of transgenic and wild-type strains)could screen initially for effects by measuring pupalcephalothorax length If no differences are found it isless likely that physiological THORNtness effects in the adultstage are detected because adults of similar size areunlikely to differ in fecundity survival and blood-feeding frequency If differences in pupal size arefound this could initiate further studies into howthese differences affect THORNtness in later life Such ex-periments could be continued with the same individ-uals because samples do not need to be destroyedwhen measuring cephalothorax length I stress thatassessment of size differences are only part of theequation Additional studies should investigate behav-ioral THORNtness differences between strains (mating hostseeking and oviposition) because they could differeven if body sizes are equal

Acknowledgments

I thank Kaitlyn Van Arsdell for technical help during therearing and measurement procedures Laura Harrington isacknowledged for support and advice during the study Thiswork was funded in part by a grant to the Regents of theUniversity of California from the Foundation for the NationalInstitutes of Health through the Grand Challenges in GlobalHealth initiative and Hatch Project NYC-139432

References Cited

Armbruster P andRAHutchinson 2002 Pupal mass andwing length as indicators of fecundity in Aedes albopictusand Aedes geniculatus (Diptera Culicidae) J Med En-tomol 39 699ETH704

Baqar S C G Hayes and T Ahmed 1980 The effect oflarval rearing conditions and adult age on the suscepti-bility of Culex tritaeniorhynchus to infection with WestNile Virus Mosq News 40 165ETH171

Blackmore M S and C C Lord 2000 The relationshipbetween size and fecundity in Aedes albopictus J VectorEcol 25 212ETH217

Briegel H 1990 Metabolic relationship between femalebody size reserves and fecundity of Aedes aegypti J In-sect Physiol 36 165ETH172

Charlwood J D 2003 May the force be with you measur-ing mosquito THORNtness in the THORNeld pp 243 InW Takken andT W Scott [eds] Ecological aspects for application ofgenetically modiTHORNed mosquitoes Kluwer Academic Pub-lishers Dordrecht The Netherlands

Christophers S K 1960 Aedes aegypti (L)ETHthe yellow fe-ver mosquito Cambridge University Press LondonUnited Kingdom

Grimstad P R and L D Haramis 1984 Aedes triseriatus(Diptera Culicidae) and La Crosse virus III Enhancedoral transmission by nutrition deprived mosquitoesJ Med Entomol 21 249ETH256

Haramis L D 1983 Increased adult size correlated withparity in Aedes triseriatus Mosq News 43 77ETH79

Hawley W A 1985 The effect of larval density on adultlongevity of a mosquito Aedes sierrensis epidemiologicalconsequences J Anim Ecol 54 955ETH964

James A A 2005 Gene drive systems in mosquitoes rulesof the road Trends Parasitol 21 64ETH67

Knight K L 1971 A mosquito taxonomic glossary VII Thepupa Mosq Syst Newsl 3 42ETH65

Lessels C M and P T Boag 1987 Unrepeatable repeat-abilities a common mistake Auk 104 116ETH121

Livdahl T P 1984 InterspeciTHORNc interactions and the r-KcontinuumETHlaboratory comparisons of geographic strainsof Aedes triseriatus Oikos 42 193ETH202

Livdahl T P and G Sugihara 1984 Non-linear interac-tions of populations and the importance of estimatingper-capita rates of change J Anim Ecol 53 573ETH580

Lounibos L P 2003 Genetic control trials and the ecologyofAedes aegypti at the Kenya coast pp 243 InW Takkenand T W Scott [eds] Ecological aspects for applicationof genetically modiTHORNed mosquitoes Kluwer AcademicPublishers Dordrecht The Netherlands

Lounibos L P N Nishimura and R L Escher 1993 Fit-ness of a treehole mosquitoETHinszliguences of food type andpredation Oikos 66 114ETH118

Lyimo E O and W Takken 1993 Effects of adult bodysize on fecundity and the pregravid rate of Anophelesgambiae females in Tanzania Med Vet Entomol 7 328ETH332

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 335

Lyimo E O W Takken and J C Koella 1992 Effect ofrearing temperature and larval density on larval survivalage at pupation and adult size of Anopheles gambiaeEntomol Exp Appl 63 265ETH271

Nasci R S 1986 The size of emerging and host-seekingAedes aegypti and the relation of size to blood-feedingsuccess in the THORNeld J Am Mosq Control Assoc 2 61ETH62

Nasci R S 1987 Adult body size and parity in THORNeld popu-lations of the mosquitoes Anopheles crucians Aedes tae-niorhynchus and Aedes sollicitans J Am Mosq ControlAssoc 3 636ETH637

Nasci R S 1990 Relationship of wing length to adult dry-weight in several mosquito species (Diptera Culicidae)J Med Entomol 27 716ETH719

Packer M J and P S Corbet 1989 Size variation andreproductive success of female Aedes punctor (DipteraCulicidae) Ecol Entomol 14 297ETH309

Paulson S L and W A Hawley 1991 Effect of body sizeon the vector competence of THORNeld and laboratory popu-lations of Aedes triseriatus for La Crosse Virus J AmMosq Control Assoc 7 170ETH175

Ponlawat A andLCHarrington 2007 Age and body sizeinszliguence male sperm capacity of the dengue vectorAedesaegypti (Diptera Culicidae) J Med Entomol 44 422ETH426

Reisen W K 2003 Lessons from the past an overview ofstudies by the University of Maryland and the Universityof California Berkeley pp 243 InW Takken and T WScott [eds] Ecological aspects for application of genet-ically modiTHORNed mosquitoes Kluwer Academic PublishersDordrecht The Netherlands

Reisen W K M M Milby and M E Bock 1984 Theeffects of immature stress on selected events in the lifehistory of Culex tarsalis Mosq News 44 385ETH395

Renshaw M M W Service and M H Birley 1994 Sizevariation and reproductive success in the mosquitoAedescantans Med Vet Entomol 8179ETH186

Scott TW A Naksathit J F Day P Kittayapong and J DEdman 1997 A THORNtness advantage for Aedes aegypti andthe viruses it transmits when females feed only on humanblood Am J Trop Med Hyg 57 235ETH239

Scott TW J LRasgonWCBlack IV andFGould 2006Fitness studies developing a consensus methodology pp210 In BGJ Knols and C Louis [eds] Bridging labo-ratory and THORNeld research for genetic control of diseasevectors Kluwer Academic Publishers Dordrecht TheNetherlands

Siegel J P R J Novak R L Lampman and B A Steinly1992 Statistical appraisal of the weight-wing length re-lationship of mosquitoes J Med Entomol 29 711ETH714

Steinwascher K 1982 Relationship between pupal massand adult survivorship and fecundity for Aedes aegyptiEnviron Entomol 11150ETH153

TakahashiM 1976 The effects of environmental and phys-iological conditions ofCulex tritaeniorhynchus on patternof transmission of Japanese encephalitis virus J MedEntomol 13 275ETH284

van den Heuvel M J 1963 The effect of rearing temper-ature on the wing length thorax length leg length andovariole number of the adult mosquito Aedes aegypti(L) Trans R Entomol Soc Lond 115 197ETH216

Received 25 September 2007 accepted 7 December 2007

336 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

y = 1110x + 0014R2 = 0904

y = 0974x + 0119R2 = 0656

14

16

18

20

22

24

26

28

30

14 16 18 20 22 24 26Cephalothorax length (mm)

Females

Males

y = 1942x + 0119R2 = 0882

y = 1419x + 0490R2 = 0554

14

16

18

20

22

24

26

28

30

08 09 10 11 12 13 14Cephalothorax width (mm)

Females

Males

Adu

lt w

ing

leng

th (m

m)

b

y = 0296x + 1560R2 = 0842

y = 0351x + 1280R2 = 0552

14

16

18

20

22

24

26

28

30

08 12 16 20 24 28 32 36 40

Pupal wet weight (mg)

Females

Males

c

a

Fig 2 Relationships between (a) pupalcephalothorax length (millimeters) and adultwing length (millimeters) (b) pupal cepha-lothorax width (millimeters) and adult winglength (millimeters) and (c) pupal wetweight (milligrams) and adult wing lengthRegression equations for males and femalesand their corresponding R2 values are indi-cated in the THORNgures

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 333

indicate that regression lines of males and femaleswere similar for cephalothorax length but not forcephalothorax width and pupal wet weight

Within 1 d after pupation no signiTHORNcant changesin cephalothorax length width or pupal wet weightwere detected (Fig 3) However shortly beforeemergence of the pupa both cephalothorax width andwet weight signiTHORNcantly decreased for both males andfemales (95 conTHORNdence intervals do not include ldquo0rdquo)whereas cephalothorax length remained the sameRelative weight loss of males was higher than of fe-males but not signiTHORNcantly so (t 1898 P 0065)

Repeatabilityvaluesofcephalothorax lengthwidthand pupal wet weight were 0815 0772 and 0735 formales and 0914 0859 and 0933 for females respec-tively These results indicate that measurements wereless consistent for males than for females for all three

predictors Although pupal wet weight had the highestrepeatability for females it was the lowest of the threefor males For males and females taken togethercephalothorax length measurements were most con-sistent (ie high repeatability values)

Discussion

I conclude that cephalothorax length provides thebest estimator of adult wing length This parameterhad the best model THORNt was highly repeatable and didnot change through the pupal stage I expected thismorphometric measurement to correlate the best be-cause it overlaps the pupal wing sheath Cephalotho-rax width and wet weight were more variable lessrepeatable and even signiTHORNcantly decreased shortlybefore emergence particularly the weight of the pupa

Female Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

Male Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

a

b

Fig 3 Proportional changes in cephalothorax length cephalothorax width and wet weight for (a) 20 male and (b) 26female Ae aegypti pupae relative to sizeweight within 2 h of pupation P 005

334 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

The change in shape and loss of weight may be relatedto preparations for emergence in which the imago willpush its way out probably spending much energy andlosing weight as a result Several pupae were ready toemerge at the third time measurement (44ETH48 h)because air had entered the cavity between thepharate imago and the pupal skin (Christophers 1960)

Steinwascher (1982) reported signiTHORNcant correla-tions between pupal and adult mass of Ae aegypti andalso found these relations to be stronger for femalesthan for males (r 098 for females and r 057 formales) In our study Pearson correlation coefTHORNcientswould be 092 and 074 for the correlation betweenpupal weight and adult wing length of females andmales respectively and 095 and 081 for the correla-tion between cephalothorax length and adult winglength of females and males respectively Thus theobservation that for a given pupal size male size ismore variable than female size in both our study andthat of Steinwascher (1982) suggests that this may bean inherent characteristic of male biology Final winglength has been demonstrated to depend on temper-ature shortly after emergence (van den Heuvel 1963)but conditions for our experiments were equal for allemerging adults

For Ae albopictus females strong correlations be-tween female pupal wet weight and adult wing length(R2 089) were found (Blackmore and Lord 2000)comparable with our cephalothorax length versusadult size relationship (R2 090) Armbruster andHutchinson (2002) concluded that pupal mass couldbe used reliably to predict fecundity of Ae albopictusand Ae geniculatus Our study indicates pupal mass isless desirable for predicting adult size because of itsmore variable nature A statistical analysis of severalpublished studies on the relationship between adultwing length and body weight concluded that mea-surement error is more likely with body weight (Siegelet al 1992) In addition wing length is a THORNxed char-acter whereas weight of adults may be confounded byfactors such as feeding history and gravid status (vanden Heuvel 1963 Siegel et al 1992) Because of thesedrawbacks adult dry weight was not considered incurrent study

Future studies that evaluate mosquito THORNtness (egcomparisons of transgenic and wild-type strains)could screen initially for effects by measuring pupalcephalothorax length If no differences are found it isless likely that physiological THORNtness effects in the adultstage are detected because adults of similar size areunlikely to differ in fecundity survival and blood-feeding frequency If differences in pupal size arefound this could initiate further studies into howthese differences affect THORNtness in later life Such ex-periments could be continued with the same individ-uals because samples do not need to be destroyedwhen measuring cephalothorax length I stress thatassessment of size differences are only part of theequation Additional studies should investigate behav-ioral THORNtness differences between strains (mating hostseeking and oviposition) because they could differeven if body sizes are equal

Acknowledgments

I thank Kaitlyn Van Arsdell for technical help during therearing and measurement procedures Laura Harrington isacknowledged for support and advice during the study Thiswork was funded in part by a grant to the Regents of theUniversity of California from the Foundation for the NationalInstitutes of Health through the Grand Challenges in GlobalHealth initiative and Hatch Project NYC-139432

References Cited

Armbruster P andRAHutchinson 2002 Pupal mass andwing length as indicators of fecundity in Aedes albopictusand Aedes geniculatus (Diptera Culicidae) J Med En-tomol 39 699ETH704

Baqar S C G Hayes and T Ahmed 1980 The effect oflarval rearing conditions and adult age on the suscepti-bility of Culex tritaeniorhynchus to infection with WestNile Virus Mosq News 40 165ETH171

Blackmore M S and C C Lord 2000 The relationshipbetween size and fecundity in Aedes albopictus J VectorEcol 25 212ETH217

Briegel H 1990 Metabolic relationship between femalebody size reserves and fecundity of Aedes aegypti J In-sect Physiol 36 165ETH172

Charlwood J D 2003 May the force be with you measur-ing mosquito THORNtness in the THORNeld pp 243 InW Takken andT W Scott [eds] Ecological aspects for application ofgenetically modiTHORNed mosquitoes Kluwer Academic Pub-lishers Dordrecht The Netherlands

Christophers S K 1960 Aedes aegypti (L)ETHthe yellow fe-ver mosquito Cambridge University Press LondonUnited Kingdom

Grimstad P R and L D Haramis 1984 Aedes triseriatus(Diptera Culicidae) and La Crosse virus III Enhancedoral transmission by nutrition deprived mosquitoesJ Med Entomol 21 249ETH256

Haramis L D 1983 Increased adult size correlated withparity in Aedes triseriatus Mosq News 43 77ETH79

Hawley W A 1985 The effect of larval density on adultlongevity of a mosquito Aedes sierrensis epidemiologicalconsequences J Anim Ecol 54 955ETH964

James A A 2005 Gene drive systems in mosquitoes rulesof the road Trends Parasitol 21 64ETH67

Knight K L 1971 A mosquito taxonomic glossary VII Thepupa Mosq Syst Newsl 3 42ETH65

Lessels C M and P T Boag 1987 Unrepeatable repeat-abilities a common mistake Auk 104 116ETH121

Livdahl T P 1984 InterspeciTHORNc interactions and the r-KcontinuumETHlaboratory comparisons of geographic strainsof Aedes triseriatus Oikos 42 193ETH202

Livdahl T P and G Sugihara 1984 Non-linear interac-tions of populations and the importance of estimatingper-capita rates of change J Anim Ecol 53 573ETH580

Lounibos L P 2003 Genetic control trials and the ecologyofAedes aegypti at the Kenya coast pp 243 InW Takkenand T W Scott [eds] Ecological aspects for applicationof genetically modiTHORNed mosquitoes Kluwer AcademicPublishers Dordrecht The Netherlands

Lounibos L P N Nishimura and R L Escher 1993 Fit-ness of a treehole mosquitoETHinszliguences of food type andpredation Oikos 66 114ETH118

Lyimo E O and W Takken 1993 Effects of adult bodysize on fecundity and the pregravid rate of Anophelesgambiae females in Tanzania Med Vet Entomol 7 328ETH332

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 335

Lyimo E O W Takken and J C Koella 1992 Effect ofrearing temperature and larval density on larval survivalage at pupation and adult size of Anopheles gambiaeEntomol Exp Appl 63 265ETH271

Nasci R S 1986 The size of emerging and host-seekingAedes aegypti and the relation of size to blood-feedingsuccess in the THORNeld J Am Mosq Control Assoc 2 61ETH62

Nasci R S 1987 Adult body size and parity in THORNeld popu-lations of the mosquitoes Anopheles crucians Aedes tae-niorhynchus and Aedes sollicitans J Am Mosq ControlAssoc 3 636ETH637

Nasci R S 1990 Relationship of wing length to adult dry-weight in several mosquito species (Diptera Culicidae)J Med Entomol 27 716ETH719

Packer M J and P S Corbet 1989 Size variation andreproductive success of female Aedes punctor (DipteraCulicidae) Ecol Entomol 14 297ETH309

Paulson S L and W A Hawley 1991 Effect of body sizeon the vector competence of THORNeld and laboratory popu-lations of Aedes triseriatus for La Crosse Virus J AmMosq Control Assoc 7 170ETH175

Ponlawat A andLCHarrington 2007 Age and body sizeinszliguence male sperm capacity of the dengue vectorAedesaegypti (Diptera Culicidae) J Med Entomol 44 422ETH426

Reisen W K 2003 Lessons from the past an overview ofstudies by the University of Maryland and the Universityof California Berkeley pp 243 InW Takken and T WScott [eds] Ecological aspects for application of genet-ically modiTHORNed mosquitoes Kluwer Academic PublishersDordrecht The Netherlands

Reisen W K M M Milby and M E Bock 1984 Theeffects of immature stress on selected events in the lifehistory of Culex tarsalis Mosq News 44 385ETH395

Renshaw M M W Service and M H Birley 1994 Sizevariation and reproductive success in the mosquitoAedescantans Med Vet Entomol 8179ETH186

Scott TW A Naksathit J F Day P Kittayapong and J DEdman 1997 A THORNtness advantage for Aedes aegypti andthe viruses it transmits when females feed only on humanblood Am J Trop Med Hyg 57 235ETH239

Scott TW J LRasgonWCBlack IV andFGould 2006Fitness studies developing a consensus methodology pp210 In BGJ Knols and C Louis [eds] Bridging labo-ratory and THORNeld research for genetic control of diseasevectors Kluwer Academic Publishers Dordrecht TheNetherlands

Siegel J P R J Novak R L Lampman and B A Steinly1992 Statistical appraisal of the weight-wing length re-lationship of mosquitoes J Med Entomol 29 711ETH714

Steinwascher K 1982 Relationship between pupal massand adult survivorship and fecundity for Aedes aegyptiEnviron Entomol 11150ETH153

TakahashiM 1976 The effects of environmental and phys-iological conditions ofCulex tritaeniorhynchus on patternof transmission of Japanese encephalitis virus J MedEntomol 13 275ETH284

van den Heuvel M J 1963 The effect of rearing temper-ature on the wing length thorax length leg length andovariole number of the adult mosquito Aedes aegypti(L) Trans R Entomol Soc Lond 115 197ETH216

Received 25 September 2007 accepted 7 December 2007

336 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

indicate that regression lines of males and femaleswere similar for cephalothorax length but not forcephalothorax width and pupal wet weight

Within 1 d after pupation no signiTHORNcant changesin cephalothorax length width or pupal wet weightwere detected (Fig 3) However shortly beforeemergence of the pupa both cephalothorax width andwet weight signiTHORNcantly decreased for both males andfemales (95 conTHORNdence intervals do not include ldquo0rdquo)whereas cephalothorax length remained the sameRelative weight loss of males was higher than of fe-males but not signiTHORNcantly so (t 1898 P 0065)

Repeatabilityvaluesofcephalothorax lengthwidthand pupal wet weight were 0815 0772 and 0735 formales and 0914 0859 and 0933 for females respec-tively These results indicate that measurements wereless consistent for males than for females for all three

predictors Although pupal wet weight had the highestrepeatability for females it was the lowest of the threefor males For males and females taken togethercephalothorax length measurements were most con-sistent (ie high repeatability values)

Discussion

I conclude that cephalothorax length provides thebest estimator of adult wing length This parameterhad the best model THORNt was highly repeatable and didnot change through the pupal stage I expected thismorphometric measurement to correlate the best be-cause it overlaps the pupal wing sheath Cephalotho-rax width and wet weight were more variable lessrepeatable and even signiTHORNcantly decreased shortlybefore emergence particularly the weight of the pupa

Female Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

Male Ae aegypti pupae

-010

-008

-006

-004

-002

000

002

004

006

008

010

srh 84-44srh 62-22Time post pupation

Prop

ortio

nal c

hang

e

Cephalothorax length Cephalothorax width

Wet weight

a

b

Fig 3 Proportional changes in cephalothorax length cephalothorax width and wet weight for (a) 20 male and (b) 26female Ae aegypti pupae relative to sizeweight within 2 h of pupation P 005

334 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

The change in shape and loss of weight may be relatedto preparations for emergence in which the imago willpush its way out probably spending much energy andlosing weight as a result Several pupae were ready toemerge at the third time measurement (44ETH48 h)because air had entered the cavity between thepharate imago and the pupal skin (Christophers 1960)

Steinwascher (1982) reported signiTHORNcant correla-tions between pupal and adult mass of Ae aegypti andalso found these relations to be stronger for femalesthan for males (r 098 for females and r 057 formales) In our study Pearson correlation coefTHORNcientswould be 092 and 074 for the correlation betweenpupal weight and adult wing length of females andmales respectively and 095 and 081 for the correla-tion between cephalothorax length and adult winglength of females and males respectively Thus theobservation that for a given pupal size male size ismore variable than female size in both our study andthat of Steinwascher (1982) suggests that this may bean inherent characteristic of male biology Final winglength has been demonstrated to depend on temper-ature shortly after emergence (van den Heuvel 1963)but conditions for our experiments were equal for allemerging adults

For Ae albopictus females strong correlations be-tween female pupal wet weight and adult wing length(R2 089) were found (Blackmore and Lord 2000)comparable with our cephalothorax length versusadult size relationship (R2 090) Armbruster andHutchinson (2002) concluded that pupal mass couldbe used reliably to predict fecundity of Ae albopictusand Ae geniculatus Our study indicates pupal mass isless desirable for predicting adult size because of itsmore variable nature A statistical analysis of severalpublished studies on the relationship between adultwing length and body weight concluded that mea-surement error is more likely with body weight (Siegelet al 1992) In addition wing length is a THORNxed char-acter whereas weight of adults may be confounded byfactors such as feeding history and gravid status (vanden Heuvel 1963 Siegel et al 1992) Because of thesedrawbacks adult dry weight was not considered incurrent study

Future studies that evaluate mosquito THORNtness (egcomparisons of transgenic and wild-type strains)could screen initially for effects by measuring pupalcephalothorax length If no differences are found it isless likely that physiological THORNtness effects in the adultstage are detected because adults of similar size areunlikely to differ in fecundity survival and blood-feeding frequency If differences in pupal size arefound this could initiate further studies into howthese differences affect THORNtness in later life Such ex-periments could be continued with the same individ-uals because samples do not need to be destroyedwhen measuring cephalothorax length I stress thatassessment of size differences are only part of theequation Additional studies should investigate behav-ioral THORNtness differences between strains (mating hostseeking and oviposition) because they could differeven if body sizes are equal

Acknowledgments

I thank Kaitlyn Van Arsdell for technical help during therearing and measurement procedures Laura Harrington isacknowledged for support and advice during the study Thiswork was funded in part by a grant to the Regents of theUniversity of California from the Foundation for the NationalInstitutes of Health through the Grand Challenges in GlobalHealth initiative and Hatch Project NYC-139432

References Cited

Armbruster P andRAHutchinson 2002 Pupal mass andwing length as indicators of fecundity in Aedes albopictusand Aedes geniculatus (Diptera Culicidae) J Med En-tomol 39 699ETH704

Baqar S C G Hayes and T Ahmed 1980 The effect oflarval rearing conditions and adult age on the suscepti-bility of Culex tritaeniorhynchus to infection with WestNile Virus Mosq News 40 165ETH171

Blackmore M S and C C Lord 2000 The relationshipbetween size and fecundity in Aedes albopictus J VectorEcol 25 212ETH217

Briegel H 1990 Metabolic relationship between femalebody size reserves and fecundity of Aedes aegypti J In-sect Physiol 36 165ETH172

Charlwood J D 2003 May the force be with you measur-ing mosquito THORNtness in the THORNeld pp 243 InW Takken andT W Scott [eds] Ecological aspects for application ofgenetically modiTHORNed mosquitoes Kluwer Academic Pub-lishers Dordrecht The Netherlands

Christophers S K 1960 Aedes aegypti (L)ETHthe yellow fe-ver mosquito Cambridge University Press LondonUnited Kingdom

Grimstad P R and L D Haramis 1984 Aedes triseriatus(Diptera Culicidae) and La Crosse virus III Enhancedoral transmission by nutrition deprived mosquitoesJ Med Entomol 21 249ETH256

Haramis L D 1983 Increased adult size correlated withparity in Aedes triseriatus Mosq News 43 77ETH79

Hawley W A 1985 The effect of larval density on adultlongevity of a mosquito Aedes sierrensis epidemiologicalconsequences J Anim Ecol 54 955ETH964

James A A 2005 Gene drive systems in mosquitoes rulesof the road Trends Parasitol 21 64ETH67

Knight K L 1971 A mosquito taxonomic glossary VII Thepupa Mosq Syst Newsl 3 42ETH65

Lessels C M and P T Boag 1987 Unrepeatable repeat-abilities a common mistake Auk 104 116ETH121

Livdahl T P 1984 InterspeciTHORNc interactions and the r-KcontinuumETHlaboratory comparisons of geographic strainsof Aedes triseriatus Oikos 42 193ETH202

Livdahl T P and G Sugihara 1984 Non-linear interac-tions of populations and the importance of estimatingper-capita rates of change J Anim Ecol 53 573ETH580

Lounibos L P 2003 Genetic control trials and the ecologyofAedes aegypti at the Kenya coast pp 243 InW Takkenand T W Scott [eds] Ecological aspects for applicationof genetically modiTHORNed mosquitoes Kluwer AcademicPublishers Dordrecht The Netherlands

Lounibos L P N Nishimura and R L Escher 1993 Fit-ness of a treehole mosquitoETHinszliguences of food type andpredation Oikos 66 114ETH118

Lyimo E O and W Takken 1993 Effects of adult bodysize on fecundity and the pregravid rate of Anophelesgambiae females in Tanzania Med Vet Entomol 7 328ETH332

March 2008 KOENRAADT PREDICTING ADULT SIZE OF Ae aegypti 335

Lyimo E O W Takken and J C Koella 1992 Effect ofrearing temperature and larval density on larval survivalage at pupation and adult size of Anopheles gambiaeEntomol Exp Appl 63 265ETH271

Nasci R S 1986 The size of emerging and host-seekingAedes aegypti and the relation of size to blood-feedingsuccess in the THORNeld J Am Mosq Control Assoc 2 61ETH62

Nasci R S 1987 Adult body size and parity in THORNeld popu-lations of the mosquitoes Anopheles crucians Aedes tae-niorhynchus and Aedes sollicitans J Am Mosq ControlAssoc 3 636ETH637

Nasci R S 1990 Relationship of wing length to adult dry-weight in several mosquito species (Diptera Culicidae)J Med Entomol 27 716ETH719

Packer M J and P S Corbet 1989 Size variation andreproductive success of female Aedes punctor (DipteraCulicidae) Ecol Entomol 14 297ETH309

Paulson S L and W A Hawley 1991 Effect of body sizeon the vector competence of THORNeld and laboratory popu-lations of Aedes triseriatus for La Crosse Virus J AmMosq Control Assoc 7 170ETH175

Ponlawat A andLCHarrington 2007 Age and body sizeinszliguence male sperm capacity of the dengue vectorAedesaegypti (Diptera Culicidae) J Med Entomol 44 422ETH426

Reisen W K 2003 Lessons from the past an overview ofstudies by the University of Maryland and the Universityof California Berkeley pp 243 InW Takken and T WScott [eds] Ecological aspects for application of genet-ically modiTHORNed mosquitoes Kluwer Academic PublishersDordrecht The Netherlands

Reisen W K M M Milby and M E Bock 1984 Theeffects of immature stress on selected events in the lifehistory of Culex tarsalis Mosq News 44 385ETH395

Renshaw M M W Service and M H Birley 1994 Sizevariation and reproductive success in the mosquitoAedescantans Med Vet Entomol 8179ETH186

Scott TW A Naksathit J F Day P Kittayapong and J DEdman 1997 A THORNtness advantage for Aedes aegypti andthe viruses it transmits when females feed only on humanblood Am J Trop Med Hyg 57 235ETH239

Scott TW J LRasgonWCBlack IV andFGould 2006Fitness studies developing a consensus methodology pp210 In BGJ Knols and C Louis [eds] Bridging labo-ratory and THORNeld research for genetic control of diseasevectors Kluwer Academic Publishers Dordrecht TheNetherlands

Siegel J P R J Novak R L Lampman and B A Steinly1992 Statistical appraisal of the weight-wing length re-lationship of mosquitoes J Med Entomol 29 711ETH714

Steinwascher K 1982 Relationship between pupal massand adult survivorship and fecundity for Aedes aegyptiEnviron Entomol 11150ETH153

TakahashiM 1976 The effects of environmental and phys-iological conditions ofCulex tritaeniorhynchus on patternof transmission of Japanese encephalitis virus J MedEntomol 13 275ETH284

van den Heuvel M J 1963 The effect of rearing temper-ature on the wing length thorax length leg length andovariole number of the adult mosquito Aedes aegypti(L) Trans R Entomol Soc Lond 115 197ETH216

Received 25 September 2007 accepted 7 December 2007

336 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

The change in shape and loss of weight may be relatedto preparations for emergence in which the imago willpush its way out probably spending much energy andlosing weight as a result Several pupae were ready toemerge at the third time measurement (44ETH48 h)because air had entered the cavity between thepharate imago and the pupal skin (Christophers 1960)

Steinwascher (1982) reported signiTHORNcant correla-tions between pupal and adult mass of Ae aegypti andalso found these relations to be stronger for femalesthan for males (r 098 for females and r 057 formales) In our study Pearson correlation coefTHORNcientswould be 092 and 074 for the correlation betweenpupal weight and adult wing length of females andmales respectively and 095 and 081 for the correla-tion between cephalothorax length and adult winglength of females and males respectively Thus theobservation that for a given pupal size male size ismore variable than female size in both our study andthat of Steinwascher (1982) suggests that this may bean inherent characteristic of male biology Final winglength has been demonstrated to depend on temper-ature shortly after emergence (van den Heuvel 1963)but conditions for our experiments were equal for allemerging adults

For Ae albopictus females strong correlations be-tween female pupal wet weight and adult wing length(R2 089) were found (Blackmore and Lord 2000)comparable with our cephalothorax length versusadult size relationship (R2 090) Armbruster andHutchinson (2002) concluded that pupal mass couldbe used reliably to predict fecundity of Ae albopictusand Ae geniculatus Our study indicates pupal mass isless desirable for predicting adult size because of itsmore variable nature A statistical analysis of severalpublished studies on the relationship between adultwing length and body weight concluded that mea-surement error is more likely with body weight (Siegelet al 1992) In addition wing length is a THORNxed char-acter whereas weight of adults may be confounded byfactors such as feeding history and gravid status (vanden Heuvel 1963 Siegel et al 1992) Because of thesedrawbacks adult dry weight was not considered incurrent study

Future studies that evaluate mosquito THORNtness (egcomparisons of transgenic and wild-type strains)could screen initially for effects by measuring pupalcephalothorax length If no differences are found it isless likely that physiological THORNtness effects in the adultstage are detected because adults of similar size areunlikely to differ in fecundity survival and blood-feeding frequency If differences in pupal size arefound this could initiate further studies into howthese differences affect THORNtness in later life Such ex-periments could be continued with the same individ-uals because samples do not need to be destroyedwhen measuring cephalothorax length I stress thatassessment of size differences are only part of theequation Additional studies should investigate behav-ioral THORNtness differences between strains (mating hostseeking and oviposition) because they could differeven if body sizes are equal

Acknowledgments

I thank Kaitlyn Van Arsdell for technical help during therearing and measurement procedures Laura Harrington isacknowledged for support and advice during the study Thiswork was funded in part by a grant to the Regents of theUniversity of California from the Foundation for the NationalInstitutes of Health through the Grand Challenges in GlobalHealth initiative and Hatch Project NYC-139432

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Nasci R S 1987 Adult body size and parity in THORNeld popu-lations of the mosquitoes Anopheles crucians Aedes tae-niorhynchus and Aedes sollicitans J Am Mosq ControlAssoc 3 636ETH637

Nasci R S 1990 Relationship of wing length to adult dry-weight in several mosquito species (Diptera Culicidae)J Med Entomol 27 716ETH719

Packer M J and P S Corbet 1989 Size variation andreproductive success of female Aedes punctor (DipteraCulicidae) Ecol Entomol 14 297ETH309

Paulson S L and W A Hawley 1991 Effect of body sizeon the vector competence of THORNeld and laboratory popu-lations of Aedes triseriatus for La Crosse Virus J AmMosq Control Assoc 7 170ETH175

Ponlawat A andLCHarrington 2007 Age and body sizeinszliguence male sperm capacity of the dengue vectorAedesaegypti (Diptera Culicidae) J Med Entomol 44 422ETH426

Reisen W K 2003 Lessons from the past an overview ofstudies by the University of Maryland and the Universityof California Berkeley pp 243 InW Takken and T WScott [eds] Ecological aspects for application of genet-ically modiTHORNed mosquitoes Kluwer Academic PublishersDordrecht The Netherlands

Reisen W K M M Milby and M E Bock 1984 Theeffects of immature stress on selected events in the lifehistory of Culex tarsalis Mosq News 44 385ETH395

Renshaw M M W Service and M H Birley 1994 Sizevariation and reproductive success in the mosquitoAedescantans Med Vet Entomol 8179ETH186

Scott TW A Naksathit J F Day P Kittayapong and J DEdman 1997 A THORNtness advantage for Aedes aegypti andthe viruses it transmits when females feed only on humanblood Am J Trop Med Hyg 57 235ETH239

Scott TW J LRasgonWCBlack IV andFGould 2006Fitness studies developing a consensus methodology pp210 In BGJ Knols and C Louis [eds] Bridging labo-ratory and THORNeld research for genetic control of diseasevectors Kluwer Academic Publishers Dordrecht TheNetherlands

Siegel J P R J Novak R L Lampman and B A Steinly1992 Statistical appraisal of the weight-wing length re-lationship of mosquitoes J Med Entomol 29 711ETH714

Steinwascher K 1982 Relationship between pupal massand adult survivorship and fecundity for Aedes aegyptiEnviron Entomol 11150ETH153

TakahashiM 1976 The effects of environmental and phys-iological conditions ofCulex tritaeniorhynchus on patternof transmission of Japanese encephalitis virus J MedEntomol 13 275ETH284

van den Heuvel M J 1963 The effect of rearing temper-ature on the wing length thorax length leg length andovariole number of the adult mosquito Aedes aegypti(L) Trans R Entomol Soc Lond 115 197ETH216

Received 25 September 2007 accepted 7 December 2007

336 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2

Lyimo E O W Takken and J C Koella 1992 Effect ofrearing temperature and larval density on larval survivalage at pupation and adult size of Anopheles gambiaeEntomol Exp Appl 63 265ETH271

Nasci R S 1986 The size of emerging and host-seekingAedes aegypti and the relation of size to blood-feedingsuccess in the THORNeld J Am Mosq Control Assoc 2 61ETH62

Nasci R S 1987 Adult body size and parity in THORNeld popu-lations of the mosquitoes Anopheles crucians Aedes tae-niorhynchus and Aedes sollicitans J Am Mosq ControlAssoc 3 636ETH637

Nasci R S 1990 Relationship of wing length to adult dry-weight in several mosquito species (Diptera Culicidae)J Med Entomol 27 716ETH719

Packer M J and P S Corbet 1989 Size variation andreproductive success of female Aedes punctor (DipteraCulicidae) Ecol Entomol 14 297ETH309

Paulson S L and W A Hawley 1991 Effect of body sizeon the vector competence of THORNeld and laboratory popu-lations of Aedes triseriatus for La Crosse Virus J AmMosq Control Assoc 7 170ETH175

Ponlawat A andLCHarrington 2007 Age and body sizeinszliguence male sperm capacity of the dengue vectorAedesaegypti (Diptera Culicidae) J Med Entomol 44 422ETH426

Reisen W K 2003 Lessons from the past an overview ofstudies by the University of Maryland and the Universityof California Berkeley pp 243 InW Takken and T WScott [eds] Ecological aspects for application of genet-ically modiTHORNed mosquitoes Kluwer Academic PublishersDordrecht The Netherlands

Reisen W K M M Milby and M E Bock 1984 Theeffects of immature stress on selected events in the lifehistory of Culex tarsalis Mosq News 44 385ETH395

Renshaw M M W Service and M H Birley 1994 Sizevariation and reproductive success in the mosquitoAedescantans Med Vet Entomol 8179ETH186

Scott TW A Naksathit J F Day P Kittayapong and J DEdman 1997 A THORNtness advantage for Aedes aegypti andthe viruses it transmits when females feed only on humanblood Am J Trop Med Hyg 57 235ETH239

Scott TW J LRasgonWCBlack IV andFGould 2006Fitness studies developing a consensus methodology pp210 In BGJ Knols and C Louis [eds] Bridging labo-ratory and THORNeld research for genetic control of diseasevectors Kluwer Academic Publishers Dordrecht TheNetherlands

Siegel J P R J Novak R L Lampman and B A Steinly1992 Statistical appraisal of the weight-wing length re-lationship of mosquitoes J Med Entomol 29 711ETH714

Steinwascher K 1982 Relationship between pupal massand adult survivorship and fecundity for Aedes aegyptiEnviron Entomol 11150ETH153

TakahashiM 1976 The effects of environmental and phys-iological conditions ofCulex tritaeniorhynchus on patternof transmission of Japanese encephalitis virus J MedEntomol 13 275ETH284

van den Heuvel M J 1963 The effect of rearing temper-ature on the wing length thorax length leg length andovariole number of the adult mosquito Aedes aegypti(L) Trans R Entomol Soc Lond 115 197ETH216

Received 25 September 2007 accepted 7 December 2007

336 JOURNAL OF MEDICAL ENTOMOLOGY Vol 45 no 2