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ECOLOGY, DISTRIBUTION AND BEHAVIOUR
OF ROVE BEETLE, Paederus fuscipes CURTIS
(COLEOPTERA: STAPHYLINIDAE) IN
RELATION TO HUMAN SETTINGS
MARYAM BINTI SUFIAN
UNIVERSITI SAINS MALAYSIA
2018
ECOLOGY, DISTRIBUTION AND BEHAVIOUR
OF ROVE BEETLE, Paederus fuscipes CURTIS
(COLEOPTERA: STAPHYLINIDAE) IN
RELATION TO HUMAN SETTINGS
by
MARYAM BINTI SUFIAN
Thesis submitted in fulfillment of the requirement
for the degree of
Doctor of Philosophy
January 2018
ii
ACKNOWLEDGEMENT
Bismillah-ir-rahmaan-ir-raheem
Alhamdulillah, all praises to Allah for the strengths and His blessing in
completing this thesis successfully. Special appreciation goes to my dearest
supervisor, Associate Professor Dr. Wan Fatma Zuharah for her valuable guidance,
advice and constant supervision as well as for providing necessary information
regarding the thesis from the beginning until the final stage of my PhD. study.
Without her support and counsel, I doubt that my thesis writing would go on
smoothly. Not forgotten, my appreciation to my two co-supervisors, Associate
Professor Dr. Nik Fadzly and Professor Amirul Al-Ashraf Abdullah. It was a great
privilege and honour to work and study under their guidance.
I would also like to thank the staff of Biological School for their precious
time, patience and energy in helping my study, and sincere thanks to all my friends
Sheyli, Ahbirami, Sumayyah, Rohaiyu, Yusoff, Andy, Shehnaz, Syafiqah, Khidhir,
Atiqah, and Hanis. Thank you for the friendship and memories.
I would like to express my gratitude towards my amazing family, especially
to my beloved parents, papa and mama, for their encouragement, support, love,
sacrifice and who always pray for me to do well in my study.
Finally, to my husband, Fahad, thanks for your love, understanding and for
being there for me always. To my younger sisters and brother, I am very lucky to
have you all always by my side when I am down and I never felt left out in any
situation. Not forgotten my late grandmother, Tok Ambra Charles. You’ll be in my
heart. Always.
iii
TABLE OF CONTENTS
ACKNOWLEDGEMENT ii
TABLE OF CONTENTS iii
LIST OF TABLE viii
LIST OF FIGURES ix
LIST OF PLATES xii
ABSTRAK xiv
ABSTRACT xvi
CHAPTER ONE: INTRODUCTION 1
CHAPTER TWO: LITERATURE REVIEW
2.1 Diversity of Paederus 5
2.2 General description of Paederus fuscipes Curtis 6
2.2.1 Scientific classification 6
2.2.2 Morphology 6
2.2.3 Life cycle 10
2.3 Food and predatory behaviour 13
2.3.1 Functional response of prey-predator relationship 14
2.4 Rice field crop and association with Paederus 14
2.5 Rice pests as food source for Paederus 19
2.5.1 Green leafhopper (Nephotettix virescens Distant) 19
2.5.2 Brown planthopper (Nilaparvata lugens Stål) 21
2.5.3 Zigzag leafhopper (Recilia dorsalis Motschulsky) 22
2.6 Behaviour 23
iv
2.7 Insect vision 23
2.8 Flight activity based on abiotic factors 25
2.9 Importance of Paederus 27
2.9.1 Agriculture 27
2.9.2 Medical impact on human 28
CHAPTER THREE: GENERAL METHODOLOGY
3.1 Sampling site 33
3.2 Sampling methods 34
3.3 Maintenance method of P. fuscipes 36
CHAPTER FOUR: SCAVENGER OR PREDATOR: A STUDY ON
MULTIFARIOUS ROLE OF ROVE BEETLE, Paederus fuscipes
CURTIS (COLEOPTERA: STAPHYLINIDAE) FEEDING
BEHAVIOURS
4.1 Introduction 38
4.2 Materials and Methods 40
4.2.1 Collection site of P. fuscipes and prey species 40
4.2.2 Sampling methods 41
4.2.3 Maintenance method of P. fuscipes 42
4.2.4 Experimental designs 42
4.2.4(a) Functional response study 42
4.2.4(b) Preference of prey 44
4.2.4(c) Predator’s behaviour 47
4.3 Results 50
4.3.1 Functional response study 50
4.3.2 Preference of prey 53
v
4.3.3 Predator’s behavior 57
4.3.3(a) Searching frequency behaviour of P. fuscipes on its
prey
57
4.3.3(b) Capturing behaviour of P. fuscipes on its prey 58
4.3.3(c) Feeding behaviour of P. fuscipes on its prey 59
4.4 Discussion 61
CHAPTER FIVE: SEASONAL ABUNDANCE AND FLIGHT
ACTIVITY OF A RICE PEST PREDATOR, Paederus fuscipes
CURTIS (COLEOPTERA: STAPHYLINIDAE)
5.1 Introduction 66
5.2 Materials and Methods 68
5.2.1 Study site 68
5.2.2 Experimental design 68
5.2.3 Rice field phenology 68
5.2.4 Meteorological data 69
5.2.5 Statistical analysis 69
5.3 Results 71
5.3.1 Effects of rice cultivation phases and environmental
variables on insects’ abundance
71
5.3.2 Effects of rice cultivation phases and light trap distance on
insects' distribution
73
5.3.3 Influence of the environmental variables on insects' dispersal
time
75
5.4 Discussion 78
vi
CHAPTER SIX: DISPERSAL PATTERN OF THE ROVE BEETLE,
Paederus fuscipes CURTIS IN AN ENDEMIC SUBURBAN AREA OF
PENANG
6.1 Introduction 82
6.2 Materials and Methods 84
6.2.1 Study site 84
6.2.2 Experimental design 86
6.2.2(a) Effects of the light illuminance 86
6.2.2(b) Effects of the height of building floor level 88
6.2.3 Statistical analysis 89
6.3 Results 90
6.3.1 Effects of different light illuminances and height of building
floor level and association with rice cultivation phase
90
6.3.2 Effects of light illuminance and rice cultivation phases 90
6.3.3 Effects of different height of each floor level and rice
cultivation phases
92
6.3.4 Effects of light illuminance at a three storey apartment 97
6.4 Discussion 101
CHAPTER SEVEN: PHOTOTACTIC RESPONSE AND COLOUR
PREFERENCES OF THE Paederus fuscipes CURTIS
(COLEOPTERA: STAPHYLINIDAE)
7.1 Introduction 108
7.2 Materials and Methods 109
7.2.1 Collection of P. fuscipes in the rice field 109
7.2.2 Maintenance method of P. fuscipes 109
7.2.3 Y-maze design 109
7.2.4 Paederus fuscipes attraction to different type of light sources 110
vii
7.2.5 Paederus fuscipes attraction to different coloured LED bulbs 112
7.2.6 Spectrographic Analysis 113
7.2.7 Statistical Analysis 113
7.3 Results 115
7.3.1 Paederus fuscipes attraction to light and no light (dark)
conditions
115
7.3.2 Paederus fuscipes attraction to fluorescent, LED, and
incandescent light sources
116
7.3.3 Paederus fuscipes attraction to white, blue, green and red LED
light sources
118
7.3.4 Light colour wavelength 121
7.4 Discussion 123
SUMMARY AND CONCLUSION 151
REFERENCES 158
APPENDICES
LIST OF PRESENTATIONS
LIST OF PUBLICATIONS
viii
LIST OF TABLES
Page
Table 4.1 The average maximum number of alive and dead prey
consumed per day by P. fuscipes predator. Data were
presented in mean ± SE
(n = 10).
52
Table 5.1 Total captures of P. fuscipes, dispersal time, and its associated
environmental variables according to rice cycles.
76
Table 6.1 Effects of light illumination at the ground/land floor level and
rice cultivation phase on the dispersion of P. fuscipes beetles
using two-way ANOVA.
91
Table 6.2 Effects of three different light illumination at the ground/land
floor level and four rice stages on the mean number of collected
P. fuscipes beetle
92
Table 6.3 Effects of height of each floor level and rice cultivation phase
differences on the dispersion of P. fuscipes beetles during the
main rice season using two-way ANOVA.
95
Table 6.4 Effects of different height of each floor level and four rice
stages on the mean number of collected P. fuscipes beetle
during the main rice season.
95
Table 6.5 Effects of height of each floor levels and rice cultivation phase
differences on the dispersion of P. fuscipes beetles during the
off rice season using two-way ANOVA.
96
Table 6.6 Effects of different height of each floor levels and four rice
stages on the mean number of collected P. fuscipes beetle
during the off rice season.
96
Table 6.7 Effects of light illumination at different height of each floor
levels of a three storey high-rise apartment building on the
dispersion of P. fuscipes beetles using two-way ANOVA.
100
Table 7.1 Paederus fuscipes preferences toward three different types of
light sources (fluorescent, cool white LED, and incandescent) in
binomial test experiment 1; a light and no light (dark) choice
condition. Significant values are in bold.
116
Table 7.2 Paederus fuscipes preferences toward three different types of
light sources (fluorescent, cool white LED, and incandescent) in
binomial test experiment 2; a light and light choice tests.
Significant value is in bold.
117
Table 7.3 Paederus fuscipes preferences toward four different LED light
colours (blue, green, white, and red) in binomial test experiment
3. Significant values are in bold.
120
ix
LIST OF FIGURES
Page
Figure 2.1 Electromagnetic spectrum of the visible light.
25
Figure 3.1 A schematic diagram of the experimental design (plan view).
A: housing areas; B and C: rice fields; 30 m, 55 m, 80 m and
105 m are the UV light traps that were placed biweekly for
attracting beetles.
36
Figure 4.1 The sampling site which is situated at Jalan Sejahtera Indah
(in red pin), Telok Air Tawar, mainland Penang, Malaysia.
40
Figure 4.2 The diagram above show the design of functional response
experiments.
43
Figure 4.3 The diagram above show the design of food preferences
experiment.
46
Figure 4.4 The diagram above shows the design of predator behavior
experiment.
49
Figure 4.5 Paederus fuscipes displayed the Type II (convex) functional
response model against alive and dead R. dorsalis species.
Data were plotted by means of 95% confidence intervals.
51
Figure 4.6 Paederus fuscipes displayed the Type II (convex) functional
response model against alive and dead Ni. lugens prey
species. Data were plotted by means of 95% confidence
intervals.
51
Figure 4.7 Paederus fuscipes displayed the Type II (convex) functional
response model against alive and dead N. virescens prey
species. Data were plotted by means of 95% confidence
intervals.
52
Figure 4.8 The preference of P. fuscipes on two combinations of prey
between (a) R. dorsalis and (b) N. virescens presented alive
and dead indicated by Manly’s alpha (α) (mean). Values
above α = 0.67 (defined by the broken horizontal line)
indicate preference.
54
Figure 4.9 The preference of P. fuscipes on two combinations of prey
between (a) Ni. lugens and (b) N. virescens presented alive
and dead indicated by Manly’s alpha (α) (mean). Values
above α = 0.67 (defined by the broken horizontal line)
indicate preference.
55
x
Figure 4.10 The preference of P. fuscipes on two combinations of prey
between (a) R.dorsalis and (b) Ni. lugens presented alive and
dead indicated by Manly’s alpha (α) (mean). Values above α
= 0.67 (defined by the broken horizontal line) indicate
preference.
56
Figure 4.11 Paederus fuscipes searching frequency behaviour on three
types of prey species (N. virescens, Ni. lugens and R.
dorsalis) presented in two conditions (alive and dead). Data
were given in mean ± SE.
58
Figure 4.12 Paederus fuscipes attempts to approach the selected prey
species (N. virescens, Ni. lugens and R. dorsalis) in two
conditions (alive and dead). Data were given in mean ± SE.
59
Figure 4.13 Paederus fuscipes predation behavior based on three types of
prey species (a) N. virescens, (b) Ni. lugens, and (c) R.
dorsalis. Prey was offered in alive and dead conditions in
relation to time (min) spent on feeding.
60
Figure 5.1 Mean number (±SE) of P. fuscipes captured biweekly for a
year period during the main rice season (October 2013 -
March 2014) and off rice season (March 2014 – October
2014) of the rice cultivation phases versus average
environmental variables.
72
Figure 5.2 Mean number (± SE) of P. fuscipes collected in relation to (a)
main rice season and (b) off rice season of the rice cultivation
phases and light trap distance. The lowercase letter refers to
the comparison between four rice cultivation phases on the
abundance of P. fuscipes, whereas the uppercase letter refers
to the comparison between light trap distances using two-way
ANOVA. Bars with the same letters are not significantly
different (Tukey’s HSD; P > 0.05).
74
Figure 5.3 Mean numbers of P. fuscipes collected in relation to (a) main
rice season and (b) off rice season of the rice cultivation
phases and dispersal time. The lowercase letter refers to the
comparison between four rice stages on the abundance of P.
fuscipes, whereas the uppercase letter refers to the
comparison between dispersal time of P. fuscipes beetle using
two-way ANOVA. Bars with the same letters are not
significantly different (Tukey’s HSD; P > 0.05).
77
Figure 6.1 Red colour box indicated the housing premises (A:
Apartment, H1: House 1, H2: House 2, H3: House 3), while
the colour green box indicated the rice field which is the
experimental site in Jalan Sejahtera, Telok Air Tawar,
Butterworth.
85
xi
Figure 6.2 Attraction of P. fuscipes beetles towards different height of
each floor levels of a three storey apartment during (a) the
main season and (b) the off season of the rice cultivation
phases. Data were given in mean ± SE (n = 12). Scale bars
with the same letters showed no significant differences
(Tukey’s HSD; P > 0.05).
93
Figure 6.3 Attraction of P. fuscipes beetles towards two different light
illuminances at different height of each floor levels of an
apartment building during (a) the main season, and (b) the off
season. The lowercase letter refers to the comparison between
heights of each floor levels, whereas the uppercase letter
refers to the comparison between two light illuminances on
the dispersion of P. fuscipes. Scale bars with the same letters
are not significantly different (Tukey’s HSD; P > 0.05).
99
Figure 7.1 The response rates of P. fuscipes to two different light
conditions in the light and dark choice test among fluorescent,
LED, and incandescent light sources using binomial test
design. Scale bars with the same letters showed no significant
difference (P > 0.05).
115
Figure 7.2 The response rates of P. fuscipes towards two choices of light
source between fluorescent vs incandescent, LED vs
incandescent, and fluorescent vs LED lights using binomial
test design. Scale bars with the same letters showed no
significant difference (P > 0.05).
117
Figure 7.3 The cumulative mean response rates of P. fuscipes towards
three types of light sources among fluorescent, LED, and
incandescent light sources using one-way ANOVA. Scale
bars with the same letters showed no significant difference
(Tukey’s HSD; P > 0.05).
118
Figure 7.4 The response rates of P. fuscipes to four types of LED
coloured light sources using one-way ANOVA. Scale bars
with the same letters showed no significant difference
(Tukey’s HSD; P > 0.05).
120
Figure 7.5 Light wavelength of fluorescent, LED and incandescent light
bulbs.
122
Figure 7.6 Light colour wavelength of LED white, blue, green, and red. 122
xii
LIST OF PLATES
Page
Plate 2.1 Adult of P. fuscipes. 8
Plate 2.2 The sixth sternite on the abdomen of the adult male P.
fuscipes.
9
Plate 2.3 The sixth sternite on the abdomen of the adult female P.
fuscipes.
9
Plate 2.4 Immature stages of the P. fuscipes consisted of the egg stage,
first and second larval instars and the pupal stage.
12
Plate 2.5 Components of a mature rice plant are illustrated above. A
matured rice plant consists of the stem, leaves and flower
panicles.
17
Plate 2.6 Developmental stages of rice plants. 17
Plate 2.7 Green leafhopper (Nephotettix virescens Distant). 20
Plate 2.8 Brown planthopper (Nilaparvata lugens Stål). 22
Plate 2.9 Zigzag leafhopper (Recilia dorsalis Motschulsky). 22
Plate 2.10 Paederus dermatitis occurs in the affected area of the (a) neck,
(b) leg, and (c) face. A newly infected skin will turn red and
inflammation of the skin takes place.
31
Plate 2.11 Paederus dermatitis occurs in the affected area of the (a) neck,
(b) leg, and (c) face. Exfoliation occurs where the skin’s
surface turns darker and has a scale-like appearance after a
couple of days.
32
Plate 3.1 Experimental site in the rice field areas near human residential
premises.
33
Plate 3.2 A close up of an ultraviolet (UV) suction blacklight trap
placed in the rice field.
35
Plate 3.3 Maintenance method of P. fuscipes beetles. 37
Plate 4.1 Collection of rice pests using the conventional light trap
method.
41
xiii
Plate 6.1 Three storey apartment situated 164 m away from the edge of
rice fields.
85
Plate 6.2 Landed housing areas situated 32 m away from the edge of
rice fields.
86
Plate 6.3 Sticky traps were fixed near the (a) no light source (0 lux), (b)
low light source (82 lux), and (c) bright light source (1206
lux).
87
Plate 6.4 The digital lux meter device that was used to measure the light
illuminace.
87
Plate 7.1 The Y-maze diagram of 5 cm in width, 5 cm in height, 20 cm
arm length in size, with an angle of 60° apart between both
arms and base of 25 cm in length.
110
Plate 7.2 The different types of light sources (a) fluorescent, (b) LED,
and (c) incandescent used in the Y-maze experimental design.
111
Plate 7.3 The different coloured LED lights (a) blue, (b) green, (c)
white, and (d) red used in the Y-maze experimental design
113
xiv
EKOLOGI, TABURAN DAN TINGKAH LAKU KUMBANG LEPUH,
Paederus fuscipes CURTIS (COLEOPTERA: STAPHYLINIDAE)
BERKAITAN DENGAN KEDIAMAN MANUSIA
ABSTRAK
Paederus fuscipes Curtis telah mendapat perhatian yang luar biasa sejak
kebelakangan ini kerana ia menyebabkan luka kulit yang teruk pada manusia di
negara-negara tropika. Kajian ini memberi tumpuan kepada aspek biologi dan
tingkah laku, interaksi dengan premis kediaman manusia dan pemencilan bakteria
yang berkaitan dengan P. fuscipes. Dalam kajian interaksi pemangsa-mangsa, P.
fuscipes menunjukkan tindak balas fungsi Jenis II untuk semua spesis mangsa. Pada
kepadatan mangsa yang tinggi mereka lebih banyak cenderung pada Recilia dorsalis
Motschulsky. Antara spesies mangsa, R. dorsalis dan Nilaparvata lugens Stål
biasanya disukai oleh P. fuscipes berbanding Nephotettix virescens Distant kerana
ciri-ciri badannya yang kecil dan lembut. Ini menunjukkan bahawa P. fuscipes adalah
pemangsa yang cekap terhadap mangsa yang lebih kecil, dan amat berguna dalam
mengawal perosak serangga semasa peringkat awal semaian padi. Walaupun
bermanfaat dalam agro-ekosistem, P. fuscipes semakin terkenal sebagai perosak
bandar di kawasan penduduk manusia. Kajian ini menunjukkan populasi P. fuscipes
meningkat pada bulan-bulan yang lebih panas dan lembap terutamanya semasa luar
musim padi. Ini secara tidak sengaja menyebabkan jumlah infestasi yang paling
besar dalam premis kediaman manusia, terutamanya semasa peringkat penuaian padi.
Aktiviti penerbangan P. fuscipes memuncak dari 2045 h, dengan suhu ambang antara
25-27 °C, dan kelembapan relatif 84-94% RH. Kebanyakan aktiviti penerbangan
berlaku pada malam tanpa angin, tetapi P. fuscipes mampu terbang di keadaan yang
xv
sedikit berangin. Kajian semasa menunjukkan bahawa pencahayaan terang yang
dihasilkan dari premis perumahan merupakan faktor tarikan kepada penyebaran P.
fuscipes. Selain itu, penduduk yang tinggal di tingkat atas pangsapuri bertingkat
tinggi amat terdedah kepada serangan kumbang terutamanya semasa peringkat
penanaman dan penuaian padi. Warna hijau dan biru yang dipancarkan oleh lampu
buatan manusia didapati sangat menarik kepada kumbang P. fuscipes. Oleh itu, di
hipotesiskan bahawa tarikan P. fuscipes terhadap lampu putih daripada premis
kediaman manusia di sebabkan oleh warna hijau dan biru tersebut. Oleh itu, sumber
cahaya yang mengeluarkan warna kuning atau merah gelombang cahaya disarankan
untuk pencahayaan untuk mengelakkan serangan P. fuscipes dalam tetapan manusia.
xvi
ECOLOGY, DISTRIBUTION AND BEHAVIOUR OF ROVE BEETLE,
Paederus fuscipes CURTIS (COLEOPTERA: STAPHYLINIDAE) IN
RELATION TO HUMAN SETTINGS
ABSTRACT
Paederus fuscipes Curtis has garnered tremendous interest in recent years
because it causes nasty skin lesion in humans in tropical countries. This study
focuses on the biological and behavioural aspects, the interactions with human
residential premises and the isolation of bacteria associated with P. fuscipes. In the
study of predator-prey interaction, P. fuscipes showed a Type II functional response
for all prey species. At the high prey density they consumed predominantly more on
Recilia dorsalis Motschulsky. Among the prey species, R. dorsalis and Nilaparvata
lugens Stål were commonly preferred by P. fuscipes as compared to Nephotettix
virescens Distant due to their small and soft body characteristics. This revealed that
P. fuscipes is an efficient predator of smaller prey, and is particularly useful in
regulating insect pest during rice nursery stage. Even though being beneficial in the
agro-ecosystem, P. fuscipes is gaining notoriety as urban pests in human-populated
areas. The present study showed that P. fuscipes population increased in the warmer
and humid months especially during the off rice season. This inadvertently caused
greatest number of beetle infestation in human residential premises, especially during
rice harvesting stage. Paederus fuscipes flight activity peaked from 2045 h onwards,
with threshold temperatures between 25–27°C, and relative humidity of 84–94% RH.
Most flight activity occurred under windless nights, however P. fuscipes is able to fly
under slightly windy conditions. The current study showed that bright illuminance
produced from housing premises served as attractant factor of P. fuscipes dispersion.
xvii
Besides, residents that live at the upper floor levels of high-rise apartment are more
prone for beetle infestation especially during rice growing and harvesting stage.
Green and blue hues emitted by artificial light were found particularly attractive to P.
fuscipes beetles. Hence, it is hypothesized that P. fuscipes attraction towards white
lightings produced from human settings is due to the green and blue hues.
Consequently, warm light sources that emits yellow or red light wavelengths is
recommended for lighting to avoid P. fuscipes infestations in human settings.
1
CHAPTER ONE
GENERAL INTRODUCTION
Rove beetles from the family Staphylinidae are the second largest family of
beetles after the Ichneumonidae (Hymenoptera), with an estimated 55,440 described
species (Grebennikov and Newton 2009). In general, these beetles are identified by
their slender elongated form and short elytra, making considerable portion of the
abdomen visible (Lott and Anderson 2011). Within these rove beetle members, only
the Paederus genus that could trigger the bullous contact dermatitis described as
erythematous lesions due to the vesicating fluid, paederin in their body that causes
burns on human skin whenever they are crushed (You et al. 2003). Paederin is a
vesicant toxic amide produced by the endosymbiont bacteria (Pseudomonas spp.)
which are largely found in the hemolymph of the adult female beetles (Kellner 2002,
Piel 2002). Hence, Paederus are world-wisely recognized as the agent of human
dermatitis as this beetle has remarkably caused serious health threat to the public
health (Nasir et al. 2015).
Outbreak cases were reported throughout the continents of the world within
tropical and subtropical regions of Asia including Indonesia (Vorderman 1901),
Japan (Armstrong and Winfield 1968, Armstrong and Winfield 1969), China (Sheng
and Sheng 1995, Wang et al. 2004, Huang et al. 2009), Egypt (Morsy et al. 1996,
Assaf et al. 2010, Awad et al. 2013), Iran (Zargari et al. 2003, Nikbakhtzadeh and
Tirgari 2008), Iraq (Al-Dhalimi 2008), India (Gnanaraj et al. 2007, Malvankar et al.
2011), Sri Lanka (Kamaladasa et al. 1997, Senanayake et al. 2011), Pakistan
(Dursteler and Nyquist 2004), Korea (Kim et al. 1989, Kim et al. 1995, You et al.
2003, Kim et al. 2007), Africa such as in Nigeria (George and Hart 1990, Okiwelu et
2
al. 1996), Sudan (Iserson and Walton 2012), Sierra Leone (Qadir et al. 2006),
Tanzania (Fox 1993, Poole 1998), Republic of the Congo (Vasudevan and Joshi
2010), Americas such as in the Amazon river (Mammino 2011), Venezuela (Kerdal
Vegas and Goihman Yahr 1966, Rivas et al. 2001, Cressey et al. 2013), Brazil (Lima
et al. 2015), Arizona (Claborn et al. 1999), Peru (Alva-Da´valos et al. 2002), Europe
such as in Italy (Gelmetti and Grimalt 1993, Veraldi et al. 2013), Turkey (Sendur et
al. 1999, Uslular et al. 2002), Bosnia (Croft et al. 1996) and Australia (Todd et al.
1996, Banney et al. 2000, Peters and Davies 2012) except for Antarctica as no
Paederus species was discovered in this extremely cold weather condition (Frank
and Kanamitsu 1987).
Dermatitis plague in Malaysia was first noted during the year 1919 (Raju
2002). Ever since, Paederus fuscipes Curtis beetle is increasingly common in
Malaysia and infestation in human settings has gained public attention within the
country such as in Penang (Ahmad et al. 2010, Bong et al. 2013), Kelantan (Mokhtar
et al. 1993), Terengganu (Rahmah and Norjaiza 2008) and Selangor (Heo et al.
2013). Paederus fuscipes is a notorious predator of various insect pest species in the
rice ecosystem in addition to their medical important function (Frank and Kanamitsu
1987). When it is seen epidemically, one of the factors that might influence P.
fuscipes infestation in human settings is their role as bio-control agents in the rice
fields (Manley 1977). The increasing Paederus population in the rice field
inadvertently caused the increment of paederus dermatitis reported cases especially
for those living nearby the rice field areas (Gnanaraj et al. 2007). Furthermore, rice
cultivation phases are known in resulting beetle invasion to human residential
premises. According to Bong et al. (2013a), massive dispersal of Paederus beetle
was due to human activities during the harvesting stage. Although human disruption
3
was known to trigger beetle invasion into human settings, environmental factors
might also play a role on their peak dispersal time. Neoh and Lee (2009) also stated
that under ideal climatic condition, the onset dispersal flights of most insects are
stimulated. Moreover, as these beetles are nocturnal by nature, the movement of P.
fuscipes out of the rice field into human settings is due to their attraction towards
artificial light sources from the residential premises (Lima et al. 2015). Although
certain types of light sources are known to attract most adults of P. fuscipes from
their breeding grounds into human residential premises, the spectral sensitivity and
colour preferences of this beetle is yet to be known. Interestingly, Paederus
infestation is not only limited to land houses, but as well as in high-rise apartment
buildings. Studies have shown that numerous dermatitis cases were also observed in
residents living in high-rise apartments (Raju 2002, Huang et al. 2009).
It is crucial to determine the attracting factors for P. fuscipes dispersal and to
understand the dispersal pattern of these beetles flying towards human residential
areas. Therefore, this study was proposed because less research has been done on this
species to understand their dispersal pattern and behaviour, which consequently leads
them to dispersed to human settings instead of being in their normal habitats such as
in the rice field. This research is important because P. fuscipes beetle is a significant
insect species worldwide (Frank and Kanamitsu 1987, Bong et al. 2015). The study
of P. fuscipes interactions among organisms and their environment will give us a
better understanding of factors that trigger Paederus beetle invasion to human
settings. By doing further research that includes behaviour and biology features of
this beetle, a successful control on P. fuscipes population movement could be
conducted. Therefore, preventive measures against Paederus infestation can be taken
to curb paederus dermatitis outbreak cases in the future.
4
In this study, a thorough understanding of the P. fuscipes biological aspects,
behaviour, their interactions with the rice ecosystem and bacterial community
associated with the rove beetles were evaluated. As such, this dissertation
encompasses four specific objectives and the overall goals of this dissertation were
1) To determine the feeding behaviours of P. fuscipes on three types of prey
species under various experimental trials.
2) To examine P. fuscipes abundance, distribution, and dispersal time using
UV light traps with regard to the cultivation phases of the rice cycle and
environmental parameters.
3) To evaluate the underlying factors for P. fuscipes attraction towards
human settings based on the influence of light illuminations and height of
each floor level of residential buildings.
4) To investigate the spectral wavelength properties (blue to infrared
spectra) that is most sensitive for P. fuscipes vision.
Towards the end of the study, it is hypothesized that P. fuscipes will show
significant preferences towards different prey species and density of prey. Besides,
rice cultivation phases and environmental parameters might have significant
influence on the abundance, distribution and dispersal time of P. fuscipes towards
human settings. In addition, light illuminations and height of each floor level of
residential buildings will affect P. fuscipes dispersal flight pattern towards human
settings. It is also postulated that spectral wavelength properties and intensity of light
emitted by artificial light sources trigger P. fuscipes flight behaviour.
5
CHAPTER TWO
LITERATURE REVIEW
2.1 Diversity of Paederus
According to Grebennikov and Newton (2009), more than 50, 000 staphylinid
beetles are distributed globally. Among them, with at least 650 described species of
small ‘rove beetles’ of the genus Paederus is found (Willers 2003).
Throughout the tropical as well as the temperate regions, northern and
southern of the equator, the genus Paederus are found dispersed almost everywhere
(Frank 1988). However, according to Frank and Kanamitsu (1987) there is no species
of Paederus found in Antarctica. Capinera (2008) stated that all genera of the
subtribe Paederina, which consisting of Paederus, Paederidus, and Megalopaederus
can cause paederus dermatitis which is also known as dermatitis linearis. Different
species of rove beetles are known to cause paederus dermatitis in several parts of the
world. Paederus brasilensis Erichson, also called ‘El podo’,
and Venezuelan species, Paederus columbinus Laporte (Singh and Ali 2007) were
reported to cause dermatitis in South America. Nairobi fly or Kenya fly such
as Paederus eximius Reiche and Paederus sabaeus Erichson are two common beetle
species which are the causal organism for keratoconjuctivitis in East Africa
(Williams 1993). However, Mbonile (2011) stated that the conjunctivitis caused by
Paederus beetles is rare throughout the world.
In contrast with other Paederus spp., the major paederus dermatitis agent in
Malaysia is the rove beetle Paederus fuscipes. It is distributed to all parts of the
country in marshes and rice fields (Manley 1977).
6
Wetland or moist environmental conditions such marshes, riverine and crop
fields are habitats that are well adapted by the Paederus spp. Manley (1977) stated
that among the species living under moist conditions, some have adapted their life
cycles according to seasonal variations. There is only single annual breeding season
in the temperate-zone species. Conversely, in the tropics the breeding season of the
Paederus is closely associated with the amount of rainfall that normally provides the
ideal condition for this beetle to thrive (Ghoneim 2013).
2.2 General description of Paederus fuscipes Curtis
2.2.1 Scientific classification
The species Paederus fuscipes is from a genus of small beetles known as
Paederus of the family Staphylinidae in the order Coleoptera. This coleopteran
beetle comes under the class Insecta of the Arthropoda phylum of the kingdom
Animalia. The rove beetle is also commonly known as the 'Beetle Tomcat' as P.
fuscipes has a similar shape that looks like an American fighter aircraft, called
TOMCAT. In Malaysia, it is locally known as ‘semut semai’, ‘semut kayap’ or
‘charlie’ (Raju 2002).
2.2.2 Morphology
Similar to other beetles in the order Coleoptera, rove beetles have hardened
forewings that cover the flight wings. Among the species of the rove beetles, there
are considerable variations amongst them. Size range is from 1 to 35 mm with the
most is in the 2–8 mm ranges. Besides, they normally have an elongated body form
with some being ovoid in shape. Being made up of a slender body form with short
elytra which are wider than their pronotum and by having sclerotized abdominal
segment is the main characteristic of a Paederus beetle. The elytron is barely longer
7
than the combined width of its elytra with a substantial portion of their abdomen is
exposed.
Paederus beetles have black, blue and red body markings and sometimes
even whole body is black in colour. Compared with other rove beetles, the P.
fuscipes species have brighter colour with blue or green metallic coloured elytra and
many consisted with black and striking orange or red colouration on the abdomen.
By having these aposematic colours on their body showed a warning sign to repel
possible predators (Mullen et al. 2009).
Generally, an adult P. fuscipes is approximately 1 mm in width and 7-8 mm
in length, which consists of the head, thorax, elytra and the abdomen (Plate 2.1). The
abdominal segments I to IV are usually bright orange or red in colour, whereas the
abdominal segments V and VI is black in colour. Their appendages are of
bicolourous colour with partly orange and black. For instance, their 11 segmented
flilliform antennae are mostly black while the first four basal segments are orange in
colour. The fore legs, middle legs and hind legs are mostly orange but darkening can
be seen around the femur which is more obvious on the basal part of the femur
particularly on the hind legs.
8
Plate 2.1 Adult of P. fuscipes.
The sternum is the ventral portion of an arthropod thorax or abdomen and is
further divided into subunits called sternites (Lawrence and Slipinski 2013). Sternites
of the arthropod are modified on the terminal abdominal segments (6th segment) so
as to form part of the functional genitalia that are normally reduced in size and
development. Adult male and female of a P. fuscipes beetle is differentiated by
identifying on the sixth sternite of the ventral posterior part of the abdomen. For
example, there is a narrow median excision or a small grove on the sixth abdominal
sternite of the male adult (Plate 2.2). However, on the female adult, the surface of the
sixth abdominal sternite is smooth without the grove (Plate 2.3).
9
Plate 2.2 The sixth sternite on the abdomen of the adult male P. fuscipes.
Plate 2.3 The sixth sternite on the abdomen of the adult female P. fuscipes.
10
2.2.3 Life cycle
According to Manley (1977), P. fuscipes undergoes a complete
metamorphosis (holometabolous) life cycle in approximately two to three weeks
which includes the egg, larva (two instars), pupa and adult stages. As reported by
Bong et al. (2012), about four to six days for the eggs to hatch and before reaching
adulthood, they undergo three immature stages which are the 1st larva instar, L1
(three to five days development time), 2nd larva instar, L2 (five to seven days
development time) and pupa (three to four days development time). The egg is about
0.5-1.0 mm in diameter, spherical in shape and yellowish white or creamy in colour.
Once the egg hatches, the L1 larva measuring 2.0 mm is whitish in colour and
translucent. After few hours, the L1 stage becomes slightly darker in colour. The L2
larva is campodeiform in shape and about 5.0-6.0 mm in length. At this stage, the
larva has well developed legs, a head and have distinguishable thorax and usually
with ten abdominal segments. Normally both L1 and L2 stages have darkened heads,
chewing mouthparts with noticeable spiracles along the sides of its body. The pupal
stage is about 4 mm in length bare, off-white to yellowish-tan in colour at maturity
(Plate 2.4). The pupa is generally immobile.
Although each stage of the development time between every individual
varies. The incubation period of most eggs increased with decreasing temperatures
(Frank and Kanamitsu 1987). In contrast, the development time and adult longevity
are shortened in hotter temperature with an increased in reproductive rate (Bong et
al. 2012). Furthermore, the adult has a longer life span of up two to three months in
cool areas.
11
Nasir and Akram (2012) reported that P. fuscipes females preferred damp
porous soils rich in decaying organic matter to lay their eggs compared with dry
sandy and clay soils as their eggs need moist condition to live.
According to Bong et al. (2013b), larvae were highly susceptible to dry
condition due to the high cuticular permeability (CP) and high percentage total body
content (%TBC). In contrast, the pupa and adult stage of the P. fuscipes beetles have
lower CP that enables them to tolerate in xeric environment (Danks 2000, Hull-
Sanders et al. 2003). As a result, they can only inhabit hygric areas as this trait curbs
divergence of P. fuscipes into different ecological zone as their larvae are too fragile
and need humid environment to survive (Ghoneim 2013). Thus, in the rice field, P.
fuscipes larvae are normally found on tillers of the rice plants, in soil cracks and
crevices as this area is moist and cool which are appropriate for the larvae
development.
12
i) Egg stage ii) First larval instar
iii) Second larval instar iv) Pupa
Plate 2.4 Immature stages of the P. fuscipes consisted of the egg stage, first and
second larval instars and the pupal stage.
13
2.3 Food and predatory behaviour
Paederus is a predator in nature (Triplehorn and Johnson 2005). Many rove
beetle species are predators of other living creatures and invertebrates, also feeds on
animals matter and decaying vegetables. On the whole, their food intake includes just
about anything apart from the living tissues of the higher plants. Paederus fuscipes is
a polyphagous predator during the adults and larval stages (Frank and Kanamitsu
1987, Manley 1977).
In general, staphylinid beetles are saprophagous feeders (or scavengers).
However, other subfamilies such as Steninae, Paederinae including Staphylininae
had evolved from saprophagy to carnivorous feeding behaviour, making most of the
Staphylinidae, tens of thousand species facultative predators (Frank and Thomas
2002).
Depending on its hunger conditions, both the adult and larva of the P.
fuscipes show some searching behaviour before confronting its prey (Manley 1977).
If the hunger motivation is high, once the prey is offered, P. fuscipes will directly
attack its prey. Both predatory adults and larvae capture their prey using their
mandibles as well as their mouthparts. For instance, like most staphylinid beetles,
during attacking, P. fuscipes will seize its prey by abruptly moving its mandibles in a
stabbing motion then grabbing them by its mouthparts and hold it with the first and
second pairs of legs before start feeding (Aloszynski and Olszanowski 2013).
Based on a study by Manley (1977), P. fuscipes is an aggressive predator on
the green leafhoppers, particularly on the nymphal stage in the rice fields of West
Malaysia. However, its diet also includes other insects like the planthoppers, leaf
rollers, thrips and many other soft body pests in the rice fields (Nasir et al. 2012,
Padmavathi et al. 2008).
14
2.3.1 Functional response of prey-predator relationship
Jeschke et al. (2002) stated that functional response is one of the key
characteristics of a predator-prey system. It requires the estimation of two basic
principles; the process of searching (searching rate or attack coefficient) of a
predator, and the time taken to fight, subdue, and consume a prey (also known as the
handling time) (Holling 1959). According to Murdoch and Oaten (1975), the
functional response helps to determine the efficacy of a predator in regulating its
prey populations using predator-prey interaction model. Predator-prey interaction
model is the relationship between the availability of prey number and the number of
prey killed by a predator (Holling 1959).
Holling (1959) classified the functional response of predators into three main
categories; Type I is a linear response with zero intercept where rate of prey capture
is proportional to prey density which levels off to a plateau when it reaches the
maximum attack rate (i.e. filter feeders), Type II functional response is a negatively
accelerated response where the rate of prey capture increases with the prey density at
a decreasing rate towards a maximum value (i.e. commonly shown by predators
dealing with a single prey species). Conversely, Type III is a sigmoidal (S-shaped)
response where the rate of prey capture at first increases with prey density at a
positively accelerated rate, but finally approached a negatively accelerated from at
high prey densities under the influence of handling time or satiation (i.e. shown by
predators that learns while foraging or prey that has refuge in the predation arena).
2.4 Rice field crop and association with Paederus
An annual grass in the family Gramineae, known as rice is categorized to the
genus Oryza that consist of twenty-two wild rice species distributed throughout the
15
tropical, sub-tropical, and temperate regions, but only two of the rice species are
cultivated: Oryza sativa (Asian rice) and Oryza glaberrima (African rice) (Seck et al.
2012). The seeds of monocot plants Oryza sativa or Oryza glaberrima are the staple
food for more than half or as much as 60% of the human population (Zeigler and
Barclay 2008), and is the main food crop in warm and humid environment such as in
the tropical region of Asia including Africa (Seck et al. 2012). In Peninsular
Malaysia, the largest granary with 98 860 ha is at Muda in Kedah while the smallest
granary area with only 1300 ha is at Seberang Perai in Penang (Karim et al. 2004).
In mainland Penang, rice is mostly cultivated in two seasons per year. The
main season which is normally from September to February and the off season which
is from March to September (Bong et al. 2013a). Depends on the variability and the
environmental condition, a rice plant normally takes three to six months to reach
maturity. In a tropical environment, a 120 days rice type takes about 60, 30, 30 days
for the vegetative, reproductive and the ripening stages respectively (Vergara 1991).
To ensure successful production of rice crop, the rice cultivation system in
mainland Penang practices four main cultivation activities consisting of ploughing,
seeding, growing, and harvesting stage. In general, the rice growth consists of three
stages, namely the (1) vegetative phase which is from germination to tillering during
the early vegetative phase, and tillering to panicle initiation during the late vegetative
phase, (2) reproductive phase which is from panicle initiation to flowering, and
finally the (3) flowering phase which is from flowering to maturing (Vergara 1991;
Rasit et al. 2016). Plate 2.5 shows the component of a mature rice plant.
Improper management of rice cultivation leads to pest infestation. Over 100
insect species are rice pests with about 20 species have major significance that can
16
cause economic damage such as the stem borers, gall midge and vectors like
leafhoppers and planthoppers which cause direct damage and transmit various
diseases to rice plant (Pathak and Khan 1994). Certain pest species may infest the
entire parts of the rice crop throughout the growing stages of rice and some can even
transmit plant viral diseases in addition to direct damages. Rice crop consists of ten
phases during its growing stage: (l) seeds germination to emergence, (2) young
seedling, (3) tillering, (4) stem elongation, (5) panicle initiation, (6) panicle
development, (7) flowering, (8) milk grain, (9) dough grain, and (l0) mature grain
stage (Salmah et al. 1998). Plate 2.6 shows the development stages of the rice plant.
During these growth stages, stem borers are generally known to infest from
the seeding stage to maturity stage of the rice plants. Stem borers from Pyralidae,
Noctuidae and Diopsidae families are considered the most serious pests of rice
worldwide (Pathak and Khan 1994). Besides, rice thrips, black bugs, rice hispa and
mealybugs are other insect pests that attack throughout the early and late vegetative
phase of the rice crop (Behera et al. 2013).
17
Plate 2.5 Components of a mature rice plant are illustrated above. A matured rice
plant consists of the stem, leaves and flower panicles.
Plate 2.6 Developmental stages of rice plants.
Stage 1: (60 Days) Stage 2: (30 Days) Stage 3: (30 Days)
Vegetation Reproduction Flowering/Maturation
18
The leafhoppers and planthoppers are significant rice pests during the
reproductive phase of the rice crop, instigating noncontagious disease known as
‘hopperburn’ and eventually caused significant yield losses (Backus et al. 2005).
These pests such as green leafhoppers, brown planthoppers and zigzag leafhoppers
are to blame for transmitting the virus of mycoplasma-like organism that causes
severe diseases (Mathur and Chaturvedi 1980).
Ripening or flowering phase of the rice growing stage is mainly divided up
into milky, dough, yellow-ripe and maturity stages (Rasit et al. 2016). During this
stage, rice pests such as both nymphs and adults of pentatomid or stink bugs feed on
the developing grains of rice specifically during the milk and dough stage that caused
partly or completely unfilled grains (Pathak and Khan 1994).
Rice pest infestation eventually attracts predatory insect into rice field areas
due to available food source. Staphylinid beetles particularly P. fuscipes is significant
in controlling insect pests of rice crop in the tropics (Ghoneim 2013). They usually
migrate to the young rice plants shortly after rice seeding and remain among the rice
crop throughout the developmental stages of the rice plants (Manley 1977). Paederus
fuscipes species is well distributed in Malaysia, and is a predator of most crop pests
in the rice field (Frank and Kanamitsu 1987). However, Bong et al. (2013a) stated
that P. fuscipes infestation at residential premises, mostly occurred once their habitat
is severely disturbed and destroyed when field was being ploughed and during
harvesting when rice stalks were cut and straws were burnt.
19
2.5 Rice pests as food source for Paederus
An ideal host for many insect species is the rice plant as every bit of the
plant’s part such as the stem, leaves even the roots are susceptible to the rice pests in
between the seeding stage until the harvesting stage of the rice grains (Ane and
Hussain 2016). They include the stem, leaf and grain suckers along with root feeders.
Several species of insect pests that attack the rice crop during the reproduction stage
are of the Cicadellidae and Delphacidae families such as the green leafhoppers,
zigzag leafhoppers and the brown planthoppers which are also major pest species in
the Malaysian rice ecosystem (Rashid et al. 1998). These insect pests are responsible
for the huge economic losses to rice yields among major rice producing countries
throughout the world (Ane and Hussain 2016). All of these pest species are the food
source for P. fuscipes (Manley 1977, Meng et al. 2016).
2.5.1 Green leafhopper (Nephotettix virescens Distant)
Among the Cicadellidae family, one of the important rice field pests is the
leafhopper. These minute insects consist of various species which feed on rice plant
by sucking the plant sap as well as from other grasses, shrubs or tress as they are
plant feeders. Some leafhopper species are vectors of plant viruses and phytoplasmas
(Stiller 2009).
One of the most important leafhopper damaging rice crops in the rice field of
South and Southeast Asia is the green leafhopper, N. virescens (Plate 2.7). According
to Hibino et al. (1979), N. virescens is the vector for rice tungro disease caused by
rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV).
Nephotettix virescens is infected by the virus on feeding from a susceptible rice plant
for at least 30 minutes (Rivera and Ou 1965), and the viruses are spread instantly
20
after acquisition to other rice crops during a short feeding period (Azzam and
Chancellor 2002).
Plate 2.7 Green leafhopper, Nephotettix virescens Distant.
Other names given to tungro including ‘penyakit merah’ in Malaysia, leaf
yellowing in India, and yellow-orange leaf virus in Thailand (Ou and Rivera 1969,
Ling 1972). Nephotettix virescens is predominantly found in low altitude rice fields.
Conducive weather such as high temperature, low rainfall, and abundant sunshine
has shown an increase of the Nephotettix spp. The population of N. virescens is
mainly numerous during the tillering and panicle initiation stages of the reproduction
phase of the rice crop (Pathak and Khan 1994). Moreover, seedling and reproduction
stages are susceptible as well. They migrate to the field soon after seedlings have
emerged.
Generally, the adults N. virescens leafhoppers are pale green in colour with
black markings on their head and wings. Furthermore, they also have two black
spots at the centre of their fore wings. Male adults are about 4.3-4.5 mm, whereas the
females are about 5.5 mm in length. They are active during daytime as well as night
time. Both the nymphs and adults of N. virescens feed by sucking the sap from the
leaves and stems with their sucking mouth parts which cause the leaves to become
1mm
21
yellowish in colour which then turn to brown and finally dry up (Singh and Singh
2014).
2.5.2 Brown planthopper (Nilaparvata lugens Stål)
Planthoppers from the Delphacidae family is an essential rice pest in
numerous Asian countries (Kiritani 1979). Planthoppers for instance the brown
planthopper, Ni. lugens is considered as a minor pest previously. However, its
population had increased tremendously to the level of a key pest, threatening the rice
production in several tropical countries mainly in South, Southeast and East Asia
(Dyck and Thomas 1979). Unlike N. virescens, Ni. lugens is an epidemic type of pest
(Kiritani 1979). It population may intensified in numbers until the whole rice crop is
completely shattered, causing severe yield losses (Dyck and Thomas 1979).
Brown planthoppers are brownish, small in size 3.5-4.5 mm and is a sucking
insect pest (Plate 2.8). Physically, adults show density-dependent wing dimorphism
with macropterous and brachypterous forms (Hasegawa 1955). The brown
planthoppers attack all plant growth stages immediately after germination until the
reproductive stage of the rice crop. According to Sogawa (1980) they are known as a
typical vascular feeder as they mainly feed on the phloem sap of the rice plant.
Brown planthoppers cause economic damage to rice crop by direct feeding (Sogawa
and Cheng 1979) where both nymphs and the adults insert their sucking mouthparts
into the plant tissues to excrete plant sap from the phloem cells which consequently
results in ‘hopper burn’ that can cause 100% crop loss (Bae and Pathak 1970).
‘Hopper burn’ happens when heavy infestations of brown planthoppers create brown
patches of dried plants. As a vector, Ni. lugens transmits two types of viruses, the
rice ragged stunt virus (Ling et al. 1978) and the rice grassy stunt virus to the rice
crops (Rivera et al. 1966).
22
Plate 2.8 Brown planthopper, Nilaparvata lugens Stål.
2.5.3 Zigzag leafhopper (Recilia dorsalis Motschulsky)
Another important rice pest from the Cicadellidae family is the zigzag
leafhopper of the R. dorsalis (Plate 2.9). Zigzag leafhopper is white with dark brown
markings (Singh and Singh 2014), and adult measures about 3.2-3.4 mm in males
and 3.8 mm in females. It is given the name zigzag due to the light brown ‘W’
shaped bands which gave a zigzag pattern on the forewings of the adults (Barrion
and Litsinger 1994). According to Pathak (1969), in South and Southeast Asia such
as Malaysia, Bangladesh, Pakistan, Japan including Taiwan, the occurrence of zigzag
leafhopper is considered common.
Plate 2.9 Zigzag leafhopper, Recilia dorsalis Motschulsky.
1mm
1mm
23
Due to its low population, it is not so much known for the damage in sucking
the leaf sap and leaf sheath of the rice plant. However, in a large population, zig-zag
leafhoppers are important as vectors of rice dwarf, tungro and yellow-orange leaf
viruses (Mathur and Chaturvedi 1980).
2.6 Behaviour
Paederus adults are active during the day, like most of the staphylinid adults,
beetles actively searching for food sources in the rice field (Manley 1977). However,
at night, artificial light sources are known to trigger Paederus dispersal flights
(Davidson et al. 2009). Inadvertently, light sources brought beetle into contact with
human beings, especially to people standing directly underneath or next to the
artificial light sources outdoor (Ghoneim 2013).
2.7 Insect vision
Insect visual systems are remarkably sophisticated and are of extraordinary
speed in processing retinal images in spite of their small eyes, tiny brain size and
comparatively few neurons (Egelhaaf and Kern 2002). The adult stage have
compound eyes which enable them to identify and respond to conspecifics,
differentiate and evade predators, locate food sources in addition to capture prey, and
depend on visual landmarks along with celestial cues for orientation and navigation
(Srinivasan 1999, Warrant and Dacke 2011), besides having the capacity to
distinguished colours.
Insects are sensitive to broad spectrum of lights ranging from the UV to red
light among the visible spectrum (Menzel et al. 1986, Peitsch et al. 1992) (Figure
2.1). However, to the eyes of most invertebrates, the UV sensitive species are
24
typically sensitive to the wavelengths of 300–700 nm (Briscoe and Chittka 2001), as
compared to human visual spectrum, which is only within the range of 400–700 nm
(Tovee 1995). Henceforth, insects are able to detect ultraviolet (UV), and other
spectrum colours using their photoreceptor cells (Osorio and Vorobyev 2005).
However, these cells within their eyes contain different rhodopsins or visual
pigments that react differently towards light of specific wavelengths (Poiani et al.
2015). Hence, the photoreceptor spectral range varies between insect species;
dichromacy in Blattoptera, trichromacy in Diptera, Hymenoptera, Hemiptera and
Orthoptera to tetrachromacy in Lepidoptera and Odonata (Menzel and Backhaus
1991, Koshitaka et al. 2008).
Colour sensitivity in the UV spectrum plays an important role for both
winged invertebrates and terrestrial insects (Honkavaara et al. 2002, Osorio and
Vorobyev 2005), in their daily behavioural activity such as in intraspecific
communication, foraging, and for circadian rhythms (Tovee 1995). This adaptive
behaviour is crucial for insect to stay alive.
Previous studies have shown that insects are especially responsive to the
shorter wavelength and higher frequency of the visible spectrum, particularly the UV
light region. Barghini and Souza de Medeiros (2012) stated that UV radiation is used
by night flying insects such as Paederus beetle for navigation. Hence, black light was
found to be particularly attractive to most Paederus individuals (Lima et al. 2015),
due to the emission of ultraviolet rays that is visible to most insects.
According to Menzel and Blakers (1976) insects normally have spectral
sensitivity peaking in the UV, blue, and green regions of the light spectrum. A study
conducted by Weiss et al. (1941) showed that approximately 60% of experimented
beetles reacted positively towards the shorter wavelength from the 365 to 528 nm
