Pheromone-Based Arrestment Behaviour of Three Species of Thysanura (Lepismatidae)
PHEROMONE-BASED ARRESTMENT BEHAVIOUR OF THREE SPECIES OF THYSANURA (LEPISMATIDAE)
by
Nathan Woodbury BSc, Simon Fraser University 2000
THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF PEST MANAGEMENT
In the Department of Biological Sciences
© Nathan Woodbury 2008
SIMON FRASER UNIVERSITY
Spring 2008
All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. APPROVAL
Name: Nathan Woodbury Degree: Master of Pest Management Title of Thesis: Pheromone-Based Arrestment Behaviour of Three Species of Thysanura (Lepismatidae) Examining Committee: Chair: Dr. J. Reynolds, Professor, S.F.U.
Dr. G. Gries, Professor, Senior Supervisor Department of Biological Sciences, S.F.U.
Dr. C. Lowenberger, Associate Professor Department of Biological Sciences, S.F.U.
Dr. G. Judd, Research Scientist, Entomologist Pacific Agri-food Research Center, Summerland, B.C.
Date Approved: APRIL 07 7000
11 SIMON FRASER UNIVERSITY LIBRARY
Declaration of Partial Copyright Licence
The author, whose copyright is declared on the title page of this work, has granted to Simon Fraser University the right to lend this thesis, project or extended essay to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users.
The author has further granted permission to Simon Fraser University to keep or make a digital copy for use in its circulating collection (currently available to the public at the "Institutional Repository" link of the SFU Library website
The author has further agreed that permission for multiple copying of this work for scholarly purposes may be granted by either the author or the Dean of Graduate Studies.
It is understood that copying or publication of this work for financial gain shall not be allowed without the author's written permission.
Permission for public performance, or limited permission for private scholarly use, of any multimedia materials forming part of this work, may have been granted by the author. This information may be found on the separately catalogued multimedia material and in the signed Partial Copyright Licence.
While licensing SFU to permit the above uses, the author retains copyright in the thesis, project or extended essays, including the right to change the work for subsequent purposes, including editing and publishing the work in whole or in part, and licensing other parties, as the author may desire.
The original Partial Copyright Licence attesting to these terms, and signed by this author, may be found in the original bound copy of this work, retained in the Simon Fraser University Archive.
Simon Fraser University Library Burnaby, BC, Canada
Revised: Fall 2007 ABSTRACT
Aggregations of the common silverfish, Lepisma saccharina L., giant silverfish, Ctenolepisma longicaudata (Escherich), and firebrat, Thermobia domestica (Packard), are mediated by non-volatile, species-specific pheromones. In dual-choice olfactometer experiments, filter paper previously exposed to male, female, or juvenile L. saccharina or C. longicaudata arrested conspecifics regardless of developmental stage or gender. Lepisma saccharina did not respond to the C. longicaudata pheromone, nor to the T. domestica pheromone. However, C. longicaudata responded to the pheromones of both L. saccharina and T. domestica, whereas T. domestica responded to the C. longicaudata but not L. saccharina pheromone. Female T. domestica were significantly arrested by (i) loose, insect-derived debris brushed from shelters, (ii) a frass mixture manually separated from loose debris, and (iii) specific amber-type frass manually separated from the frass mixture, but did not respond to other types of shelter debris or insect-altered cellulose, suggesting that T. domestica pheromone is present in amber-type frass.
Keywords:
Lepisma saccharina, Ctenolepisma longicaudata, Thermobia domestica, Thysanura, Zygentoma, Lepismatidae, pheromone, aggregation, arrestment, frass, feces.
III ACKNOWLEDGEMENTS
I would like to thank my senior supervisor, Dr. Gerhard Gries, for his
invaluable advice, patience and endless enthusiasm throughout the course of this (still ongoing) work. In addition, Mrs. Regine Gries, Dr. Grigori Khaskin, Dr.
Robert Britton and my Gries Laboratory colleages deserve heartfelt thanks for
helping me surmount many scientific obstacles.
I thank my surpervisory committee member, Dr. Carl Lowenberger for
review of my thesis and for constructive suggestions during the course of this
research. I also thank the public examiner, Dr. Gary Judd for his valuable
suggestions which have lead to many improvements of this thesis.
I would also like to thank Dave Booth for supplying Lepisma saccharina,
Michelle Tremblay for advice on the capture and rearing of all thysanuran
species, Eberhard Kiehlmann for contructive comments on manuscripts, and
Colin Zhang, Aleksander Miroshnychenko, Allen Haddrell and Michael Katz for all
of their help with chemical analyses.
I also thank Kate McLellan, Landon Woodbury, my parents and my friends
for years of unfaltering support and wisdom.
This research was supported by a Professor Thelma Finlayson Fellowship
and a Simon Fraser University Graduate Fellowship to N.W., and a Natural
Sciences and Engineering Research Council of Canada (NSERC)-Industrial
IV Research Chair to G.G. with SC Johnson Canada, Pherotech International Inc. and Global Forest Science (GF-18-2007-226 and GF-18-2007-227) as the industrial sponsors.
v TABLE OF CONTENTS
Approval ii Abstract iii Acknowledgements iv Table of Contents vi List of Figures viii
1 THYSANURAN BIOLOGY AND AGGREGATION OF PHYLOGENETICALLY ANCESTRAL INSECTS 1
1.1 THYSANURAN BIOLOGY & ECOLOGY 1 1.1.1 Phylogeny, Distribution and Morphology of Thysanura 1 1.1.2 Abiotic Conditions and Food Preferences of Thysanura 5 1.1.3 Mating Behaviour & Development of Thysanura 7
1.2 AGGREGATION BEHAVIOUR OF PHYLOGENETICALLY ANCESTRAL INSECTS 9 1.2.1 Aggregation Behaviour of Thysanura 9 1.2.2 The Role of Pheromones in Aggregations of Hexapods and Orthopteroid Insects 12 1.2.3 The Role of Pheromones in Thysanuran Aggregations .15
1.3 THE ECONOMIC IMPORTANCE OF THYSANURA 16
1.4 RESEARCH OBJECTIVES 17
2 EVIDENCE FOR AN ARRESTMENT PHEROMONE IN L. SACCHARINA AND C. LONGICAUDATA 19
2.1 INTRODUCTION 19
2.2 MATERIALS AND METHODS 21 2.2.1 Collecting and Rearing of Experimental Insects 21 2.2.2 General Bioassay Procedures 22 2.2.3 Specific Experiments 23 2.2.4 Statistical Analyses 25
2.3 RESULTS 25
vi 2.4 DiSCUSSiON 37
3 SHELTER DEBRIS AND THE ARRESTMENT PHEROMONE OF T. DOMESTICA 41
3.1 INTRODUCTION 41
3.2 MATERIALS AND METHODS 44 3.2.1 Collecting and Rearing of Experimental Insects .44 3.2.2 General Bioassay Procedures .45 3.2.3 Specific Experiments .46 3.2.4 Statistical Analyses 50
3.3 RESULTS 50
3.4 DiSCUSSiON 54
4 CONCLUSiON 60
References 61
vii LIST OF FIGURES
Figure 1.1 Photographic illustrations of the common silverfish, Lepisma saccharina (top), giant or long-tailed silverfish, Ctenolepisma longicaudata (middle), and the firebrat, Thermobia domestica (bottom) 3 Figure 2.1 Number of male, female, or juvenile L. saccharina responding to a piece of filter paper previously exposed to male, female, or juvenile L. saccharina. Numbers near bars indicate the number of insects responding to the test stimulus. An asterisk (*) indicates a significant preference for a particular test stimulus (X2 test; *P :5 0.05, **P :5 0.01). Numbers in brackets indicate numbers of non-responding insects 27 Figure 2.2 Number of male, female, or juvenile C. longicaudata responding to a piece of filter paper previously exposed to male, female, or juvenile C. longicaudata. Numbers near bars indicate the number of insects responding to the test stimulus. An asterisk (*) indicates a significant preference for a particular test stimulus (X2 test; *P :5 0.05, **P :5 0.01). Numbers in brackets indicate numbers of non-responding insects 29 Figure 2.3 Number of female L. saccharina (left) or C. longicaudata (right) responding to a piece of filter paper previously exposed to male, female, or juvenile conspecifics when stimulus contact was prohibited or allowed. Numbers near bars indicate the number of insects responding to the test stimulus. An asterisk (*) indicates a significant preference for a particular test stimulus (l test; *P :5 0.05, **P :5 0.01). Numbers in brackets indicate numbers of non-responding insects 31 Figure 2.4 Number of female L. saccharina responding to conspecific frass, scales, antennae and caudal filaments, or salivary gland contents. Numbers near bars indicate the number of insects responding to the test stimulus. An asterisk (*) indicates a significant preference for a particular test stimulus (x2 test; *P:5 0.05, **P :5 0.01). Numbers in brackets indicate numbers of non-responding insects 33
viii Figure 2.5 Number of female L. saccharina, C. longicaudata, or T. domestica responding to a piece of filter paper previously exposed to conspecific or heterospecific males, females, and juveniles. Numbers near bars indicate the number of insects responding to the test stimulus. An asterisk (*) indicates a significant preference for a particular test stimulus (X2 test; *P ~ 0.05, **P ~ 0.01). Numbers in brackets indicate numbers of non-responding insects 35 Figure 3.1 Number of female T. domestica (A) responding to shelter paper exposed to conspecifics for 3 days (experiment 1) or insect-derived debris accumulating in those shelters; and (8) responding to insect-exposed paper shelter tips, paper shelter perimeters, glass surfaces exposed to conspecifcs for 3 days, silk removed from shelters, or silk squeezed from male T. domestica. Control papers and glass were not exposed to conspecifics and did not contain insect-derived debris. Numbers within brackets indicate the number of insects responding to the test stimulus (left number) or control (right number). Subscript numbers outside of brackets indicate numbers of non-responding insects. An asterisk (*) indicates a significant preference for a particular test stimulus (X2 test; *P ~ 0.05, **P ~ 0.01) 52
ix 1 THYSANURAN BIOLOGY AND AGGREGATION OF PHYLOGENETICALLY ANCESTRAL INSECTS
1.1 THYSANURAN BIOLOGY & ECOLOGY
1.1.1 Phylogeny, Distribution and Morphology of Thysanura
Thysanura (= Zygentoma) is considered one of the oldest insect orders,
originating 350-400 million years ago, following the appearance of entognathous
hexapods (Collembola, Diplura and Protura) and preceding the appearance of
phylogenetically derived ('modern') insects (Kristensen, 1981; Kukalova-Peck,
1986; Labandeira et aL, 1988; Carapelli et aL, 2000). Thysanurans are wingless,
ectognathous and ametabolous (Adams, 1933b; Sweetman, 1938, 1939; Zungoli,
1983; Wygodzinsky, 1987; Remington, 1954; Ferguson, 1990), and therefore
represent a condition that is intermediate to that of entognathous hexapods and
other insects (Crampton, 1916; Smith, 1970; Kristensen, 1981; Carapelli et aL,
2000; Triplehorn & Johnson, 2005). There are believed to be 320-370 species of
thysanura distributed throughout the world (Wygodzinsky, 1972, Mendes, 1982,
Arnett, 1985, Ferguson, 1990, Triplehorn & Johnson, 2005) from three taxonomic
families, Lepidotrichidae, Nicoletiidae and Lepismatidae (Wygodzinsky, 1972,
1987; Arnett, 1985; Mendes, 1991; Richards & Davies, 1977). These species are found in a variety of habitats including bird, mammal and insect nests, in caves, beneath natural debris (Wygodzinsky, 1972, 1987; Gray, 1974; Tomlin, 1979;
Arnett, 1985; Ferguson, 1990; Triplehorn &Johnson, 2005) and within human structures (Spencer, 1930; Sweetman, 1938, 1939; Lindsay, 1940; Curran, 1946;
Adams, 1959; Olkowski et aL, 1991).
In North America, the three most commonly encountered species are the common silverfish, Lepisma saccharina L., the giant or long-tailed silverfish,
Ctenolepisma longicaudata (= urbana) (Escherich), and the firebrat, Thermobia domestica (Packard), (all members of the family Lepismatidae) (Swan & Papp,
1972; Wygodzinsky, 1972; Powell & Hogue, 1979; Tomlin, 1979; Ferguson,
1990; Olkowski et aL, 1991) (Figure 1.1). In addition to behavioural differences
(see below), these three species are morphologically distinct. Adult L. saccharina are 0.8-1.3 cm long and are distinguishable by their uniformly silver-grey colouration and by their antennae which are shorter than the length of the body
(Lubbock, 1873; Slabaugh, 1940; Sweetman, 1965; Mallis, 1969; Swan & Papp,
1972; Wygodzinsky, 1972; Powell & Hogue, 1979; Arnett, 1985; Ferguson, 1990;
Olkowski et aL, 1991). By comparison, T. domestica are of a similar length (0.9
1.4 cm) but display a heavily mottled, light and dark colouration and possess
antennae as long as or longer than the body (Sweetman, 1938, 1965; Slabaugh,
1940; Brett, 1962; Mallis, 1969; Swan & Papp, 1972; Wygodzinsky, 1972; Powell
& Hogue, 1979; Arnett, 1985; Ferguson, 1990; Olkowski et aI., 1991).
Ctenolepisma longicaudata are 1.3-1.9 cm in
2 Figure 1.1 Photographic illustrations of the common silverfish, Lepisma
saccharina (top), giant or long-tailed silverfish, Ctenolepisma
longicaudata (middle), and the firebrat, Thermobia domestica
(bottom).
3 4 length, uniformly grey coloured and possess antennae as long as or longer than the body length (Slabaugh, 1940; Sweetman, 1965; Mallis, 1969; Swan & Papp,
1972; Wygodzinsky, 1972; Powell & Hogue, 1979; Arnett, 1985; Ferguson,
1990).
1.1.2 Abiotic Conditions and Food Preferences of Thysanura
Within human dwellings and in rearing facilities, L. saccharina, C. longicaudata and T. domestica forage for food and water during nocturnal periods and during diurnal periods retreat to dark shelters (Spencer, 1930; Meyer, 1932; Sweetman,
1938, 1939; Lindsay, 1940; Curran, 1946; Adams, 1959; Smith, 1970; Olkowski et aL, 1991), where temperature and humidity are optimal for development and survival of eggs (Adams, 1933a, 1959; Sweetman, 1938, 1939; Lindsay, 1940;
Spencer, 1959; Tremblay & Gries, 2006). Survival and development of L. saccharina is optimal at relatively low temperatures (22-32 °C) (Sweetman, 1939;
Adams, 1959; Mallis, 1969; Powell & Hogue, 1979; Olkowski et aL, 1991) and high humidity (75-97% rh) (Sweetman, 1939; Adams, 1959; Mallis, 1969;
Olkowski et aL, 1991), whereas T. domestica require high temperatures (32-44
°C) (Spencer, 1930; Adams, 1933a, b, 1959; Austin & Richardson, 1941;
Sweetman, 1938; Mallis, 1969; Powell & Hogue, 1979; Olkowski et aL, 1991) and can survive at various humidities (50-98% rh) (Adams, 1933a, 1959; Austin &
Richardson, 1941; Sweetman, 1938). For these reasons, L. saccharina are
5 commonly found in or near cool, damp habitats such as water pipes (Sweetman,
1939; Zungoli, 1983), whereas T. domestica are commonly found near heat sources such as boilers, ovens or steam pipes (Spencer, 1930; Brett, 1962;
Powell & Hogue, 1979; Zungoli, 1983; Olkowski et aI., 1991). The optimum conditions for development and survival of C. longicaudata (24°C, 55-82% rh)
(Lindsay, 1940) are intermediate to those of L. saccharina and T. domestica. This allows C. longicaudata to reside in the preferred habitats of both species
(Lindsay, 1940; Mallis, 1969; Zungoli, 1983).
Lepisma saccharina, C. longicaudata and T. domestica are all omnivorous and survive in culture and in nature on algae, lichen, fungi, plant-derived materials such as pollen, flour, oats, wheat, cotton, yeast, starch, paper, cardboard and rayon, as well as animal-derived materials such as beef, glues, conspecific eggs, exuviae, setae, scales and the bodies of dead conspecifics (Jackson, 1886;
Spencer, 1930, 1959; Adams, 1933a, 1959; Sweetman, 1938, 1939; Lindsay,
1940; Austin & Richardson, 1941; Mallis, 1941, 1969; Berger, 1945; Wall, 1953;
Brett, 1962; Smith, 1970; Ferguson, 1990; Olkowski et aI., 1991). Thysanurans commonly consume and damage cellulosic materials such as paper and rayon, and employ endogenous cellulases to digest these materials (Zinkler et aI., 1986;
Zinkler & G6tze, 1987; Treves & Martin, 1994). Despite this, a diet of paper alone results in rapid mortality of T. domestica colonies (Adams, 1933a). Therefore, it is likely that thysanuran survival requires a varied diet containing both cellulose and animal derived materials. This is further exemplified by the fact that the
6 thysanuran alimentary tract contains enzymes capable of digesting starch, fat and protein (Wall & Swift, 1954; Zinkler & Gotze, 1987; Zinkler & Polzer, 1992).
1.1.3 Mating Behaviour & Development of Thysanura
Thysanuran reproduction requires both genders to engage in a complex courtship ritual before males indirectly transfer sperm to females. In L. saccharina, males and females initiate courtship by moving in tandem whilst mutually antennating, typically near a vertical structure. The male then rapidly spins a horizontal mat of reproductive threads from his phallic glands (Bitsch,
1990) as well as a line of threads between the ground and any nearby vertical structure. He then deposits a proteinaceous (Romano, 1989) spermatophore on the horizontal substrate near the threads. With her cerci and caudal filament raised, the moving female eventually contacts the threads which signals the location of the spermatophore (Sturm, 1956; Schaller, 1971; Sturm, 1987;
Ferguson, 1990; Proctor, 1998). The courtship ritual of T. domestica differs from that of L. saccharina in that a male T. domestica (i) conveys the location of spermatophores to a female by flicking her with his antennae and (ii) uses threads to excite the female and to delineate the mating area (Spencer, 1930;
Sweetman, 1938; Sturm, 1987; Romano, 1989; Proctor, 1998). The mating ritual of C. longicaudata is not well understood. However, it has been postulated that the male directly transfers his spermatophore to the vagina of the female
(Lindsay, 1940).
7 Female thysanurans oviposit light-coloured, elliptically-shaped eggs (0.8-1.29 mm length) year round into narrow crevices that offer optimal temperature and humidity for egg development (Adams, 1933a, b, 1959; Sweetman, 1938, 1939;
Lindsay, 1940; Spencer, 1959; Swan & Papp, 1972; Olkowski et aI., 1991). A female L. saccharina can oviposit 1-3 eggs per day up to an average lifetime total of 50 eggs (Sweetman, 1939) which at optimal conditions require 14-56 days to hatch (Sweetman, 1939; Swan & Papp, 1972). Female T. domestica lay approximately one egg per day (Adams, 1933a), each egg requiring 12-18 days to hatch (Adams, 1933a, b; Sweetman, 1938). Finally, female C. longicaudata oviposit eggs in batches of 2-20 (56 eggs per year) which hatch in 34-60 days
(Lindsay, 1940, Mallis, 1969). Thysanuran nymphs develop ametabolously and reach sexual maturity in 7-16 weeks (Adams, 1933a, b, 1959; Sweetman, 1938,
1939), or 2.5-3 years in the case of C. longicaudata (Lindsay, 1940). Juveniles and adults molt continuously throughout their 1-7 year lifespan (Adams, 1933a;
Sweetman, 1938, 1939; Lindsay, 1940; Swan & Papp, 1972; Olkowski et aI.,
1991), thus allowing replacement of lost appendages and scales (Adams, 1933a;
Buck & Edwards, 1990) or shedding of injurious fungi (Ferguson, 1990) with each consecutive molt.
8 1.2 AGGREGATION BEHAVIOUR OF PHYLOGENETICALLY ANCESTRAL INSECTS
1.2.1 Aggregation Behaviour of Thysanura
Insect aggregations occur when multiple individuals are attracted to, or arrested at a stimulus, resulting in a population increase at or near the stimulus site
(Dethier et aI., 1960; Shorey, 1973; Borden, 1985; Wertheim et aI., 2005). This attraction or arrestment is accomplished if the stimulus slows the linear progression of insects by either reducing the speed of locomotion or by increasing the rate of turning near the source of the stimulus (Dethier et aI.,
1960). Lepisma saccharina, C. longicaudata and T. domestica all exhibit aggregation behaviour, particularly in human dwellings where temperature and humidity are sufficiently high to support insect growth and development throughout the year (Spencer, 1930; Adams, 1933a, b; Sweetman, 1938, 1939;
Lindsay, 1940; Curran, 1946; Mallis, 1969; Tremblay, 2002; Tremblay & Gries,
2006). These aggregations typically consist of adult and juvenile conspecifics.
However heterospecific thysanurans with similar temperature and humidity requirements can be found aggregating together in low numbers within rearing chambers (NW, personal observation). Initially, an aggregation forms because thysanurans seek dark shelters with a restricted entrance (Spencer, 1959;
Tremblay, 2002; Tremblay & Gries, 2006), favourable temperature or humidity, and in close proximity to food or water (Spencer, 1930; Lindsay, 1940; Mallis,
1969; Olkowski et aI., 1991; Zungoli, 1983). Food availability within the shelter
9 itself does not appear to influence shelter choice (Tremblay, 2002; Tremblay &
Gries, 2006). As individuals aggregate in a preferred shelter, they inevitably
contaminate it with feces, shed scales, exuviae, broken appendages, setae,
gregarine parasites, reproductive silk, spermatophores, eggs and saliva (Adams,
1933a, 1959; Sweetman, 1938, 1965; Lindsay, 1940; Mallis, 1969; Sidebottom,
1996). These contaminated shelters are then capable of arresting con- and
heterospecifics (Tremblay, 2002; Tremblay & Gries, 2003) that contribute to the
expansion and perpetuation of large aggregations (Tremblay & Gries, 2006).
Aggregating individuals maintain close contact with, and typically rest their
antennae and caudal appendages on their nearest neighbour(s) (Tremblay,
2002; Tremblay & Gries, 2003; NW, personal observation). Movement of any
individual within that aggregation is thus physically detected by neighbouring
insects, inducing them to move as well. This behaviour, common to T. domestica,
L. saccharina, C. longicaudata and the closely related microcoryphian Petrobius
brevistylis Carpenter (Delany, 1959), suggests that aggregations facilitate
increased vigilance against predation or other physical threats by either alerting
individuals to physical disturbances within the aggregation or by forming
aggregations in areas of reduced predation (Adams, 1933a; Delany, 1959;
Edwards & Reddy, 1986; Kukalova-Peck, 1986). Aggregative behaviour could
evolve if predation, parasitism or destruction of individuals by abiotic factors
occur less frequently when individuals stay in groups rather than in isolation
10 (Sweetman, 1938). However, this concept has not been directly tested
experimentally with thysanurans.
Alternatively, aggregation may result in improved reproductive success of
individuals by increasing the rate of encounter with potential mates (Joosse,
1970; Verhoef & Nagelkerke, 1977; Wileyto et aI., 1984; Wertheim et aI., 2005).
In thysanurans, close proximity between males and females increases the
females' encounters with males' reproductive threads which subsequently
increases spermatophore uptake (Spencer, 1930; Sweetman, 1938; Schaller,
1971; Sturm, 1987; Romano, 1989; Ferguson, 1990; Proctor, 1998). In non
aggregating insects, male-female encounters are typically temporary and are
often mediated by long-range, airborne pheromones (Mayer & McLaughlin, 1991)
or by auditory signals (Dahm et aI., 1971; Hart, 2006). No such modes of
communication are known to occur in any thysanuran species. Remaining within
aggregations from hatching to adulthood would ensure that an individual
thysanuran can always locate mates, spermatophores and oviposition sites.
Persistent aggregations might also benefit non-reproductive juveniles that could
fail to find resources or potential future mates if they dispersed too far from the
aggregation.
Increased spermatophore uptake and mate encounter is believed to underlie
aggregation behaviour in many other hexapods and orthopteroid insects, such as
Blattodea (Wileyto et aI., 1984), Collembola (Joosse, 1970, Verhoef &
11 Nagelkerke, 1977), Dermaptera (Walker et aI., 1993) and Orthoptera (Sexton &
Hess, 1968).
In addition to improved predator vigilance and mate access, thysanurans may obtain other physiological benefits as members of an aggregation. Group-reared, juvenile T. domestica reportedly exhibit faster development, increased longevity and greater fecundity than individuals that are reared in isolation (Sweetman,
1938). Similar observations have been made in the German cockroach, Blatfella germanica L. (Ishii & Kuwahara, 1967) and in one isopod species, Armadillidium vulgare (Latreille) (Takeda, 1980), however contrary observations have also been reported (Wileyto et aI., 1984). Ultimately, it is not known how aggregation mediates these particular physiological benefits.
1.2.2 The Role of Pheromones in Aggregations of Hexapods and Orthopteroid Insects
Like thysanurans, many hexapods and orthopteroid insects are known to aggregate within confined spaces in groups comprised of juvenile and adult insects of both genders. Cohesion of these aggregations requires that both juvenile and adult insects produce and/or aggregate in response to a perceived pheromone. Pheromone production and aggregation response to pheromone by both males and females, as well as juveniles, is known from Blattodea (Bell et aI.,
1973; Roth & Cohen, 1973; Brossut et aI., 1974; Metzger & Trier, 1975; Suto &
12 Kumada, 1981; McFarlane & Alii, 1986), Collembola (Verhoef et aI., 1977;
Joosse & Koelman, 1979; Verhoef, 1984), Dermaptera (Sauphanor, 1992;
Sauphanor & Sureau, 1993; Walker et aI., 1993), Orthoptera (Sexton & Hess,
1968; Fuzeau-Braesch et aI., 1988; Obeng-Ofori et aI., 1994b; Dillon et aI., 2002) and the symphylan S. immaculata (Reeve & Berry, 1976). Moreover, some species of Blattodea (Ishii & Kuwahara, 1968; Ishii, 1970; Bell et aI., 1972; Roth
& Cohen, 1973; Metzger & Trier, 1975; Rust & Appel, 1985), Collembola
(Verhoef et aI., 1977), Dermaptera (Sauphanor & Sureau, 1993) and Isoptera
(Reinhard et aI., 1997; Reinhard & Kaib, 2001) perceive and respond to aggregation pheromone of heterospecific individuals.
Most of the known aggregation pheromones of hexapods and orthopteroids have not yet been chemically identified. Behavioural experiments that allowed or prevented contact with the pheromone source have revealed that the volatility of pheromones varies greatly between orders. Pheromones of Collembola (Verhoef et aI., 1977; Leonard & Bradbury, 1984; Manica et aI., 2001) and Orthoptera
(McFarlane et aI., 1983; Fuzeau-Braesch et aI., 1988; Obeng-Ofori et aI., 1993,
1994a, b; Torto et aI., 1994; Dillon et aI., 2000) are volatile and attract conspecifics to the source, whereas pheromones of Isoptera (Reinhard & Kaib,
1995; Reinhard et aI., 1997; Reinhard & Kaib, 2001) and Symphyla (Reeve &
Berry, 1976) lack volatility, and rely on chance encounter and physical contact by conspecifics to elicit their arrestment behaviour.
13 A complex aggregation pheromone is known from two species of Blattodea,
B1attella germanica (Sakuma & Fukami, 1990, 1991, 1993a, b; Mori &
Fukamatsu, 1993; Sakuma et aI., 1997a, b) and Eublaberus distanti (Kirby)
(Brossut, 1979). The pheromone consists of a volatile long-range component that
attracts conspecifics from a distance and a non-volatile contact component that
arrests them at the pheromone source.
Aggregation pheromones have been isolated from the labial glands of Isoptera
(Kaib & Ziesmann, 1992; Reinhard & Kaib, 1995,2001; Reinhard et aI., 1997,
2002), the mandibular glands of two species of Blattodea (Brossut et aI., 1974;
Brossut, 1979) and the tibial glands of two species of Dermaptera (Sauphanor,
1992; Sauphanor & Sureau, 1993). Also, feces that often contains hindgut
secretions or bacteria is believed to be the source of aggregation pheromone of
Collembola (Verhoef, 1984), Orthoptera (Gillet et aI., 1976; McFarlane et aI.,
1983; Obeng-Ofori et aI., 1994b; Torto et aI., 1996; Dillon et aI., 2000, 2002), one
terrestrial isopod (Takeda, 1980), one species of Dermaptera (Walker et aI.,
1993) and five species of Blattodea (Ishii & Kuwahara, 1967, 1968; Ishii, 1970;
Bell et aI., 1973; Roth & Cohen, 1973; Block & Bell, 1974; Metzger & Trier, 1975;
Brossut, 1979; Suto & Kumada, 1981; Wendler &Vlatten, 1993; Scherkenbeck et
aL,1999).
14 1.2.3 The Role of Pheromones in Thysanuran Aggregations
The study by Tremblay & Gries (2003) provides the only evidence for an aggregation pheromone in a thysanuran species. In dual-choice bioassays, individual T. domestica demonstrated a preference for filter paper that had previously been exposed to conspecific insects as opposed to unexposed paper.
Paper previously exposed to male, female or juvenile insects arrested conspecifics regardless of their developmental stage or gender, but failed to do so when insects were prohibited from contacting it. From these observations it was concluded that female, male and juvenile T. domestica all produce and perceive a non-volatile contact aggregation pheromone that elicits arrestment behaviour. In contrast, insect-derived frass and scales that are typically found on insect-exposed papers failed to elicit arrestment responses. Therefore, the precise source of the T. domestica arrestment pheromone remains unknown.
Conceivably, arrestment of T. domestica may be mediated by physical or chemical alterations made to cellulose during feeding. Additionally, the pheromone of T. domestica is effective at arresting C. longicaudata but fails to arrest L. saccharina. Intra- and interspecific pheromone production and perception among C. longicaudata and L. saccharina have yet to be tested.
15 1.3 THE ECONOMIC IMPORTANCE OF THYSANURA
Thysanurans typically enter human dwellings on infested materials carried by humans or they wander in from adjacent infestations (Olkowski et aI., 1991).
When an aggregation is established, nearby fabrics, paste and paper become physically damaged or stained as a result of insect feeding and defecation
(Jackson, 1886; Marlatt, 1915; Spencer, 1930; Sweetman, 1938, 1939, 1965;
Lindsay, 1940; Austin & Richardson, 1941; Berger, 1945; Curran, 1946; Wall,
1953; Mallis et aI., 1958; Brett, 1962; Mallis, 1969; Zungoli, 1983; Powell &
Hogue, 1979; Olkowski et aI., 1991). Damage is usually localized and slow to develop however, the cryptic nature of these insects allows them to remain undetected for enough time that damage can become extensive (Jackson, 1886;
Mallis, 1990). Of particular importance is damage to historical, rare or valuable items in long-term storage (Jackson, 1886; Austin & Richardson, 1941; Mallis,
1969). With the rare exception of human allergic reaction to thysanuran scales
(Witteman et aI., 1995), these insects are not known to physically harm humans.
Consequently, control of thysanurans is typically motivated solely by homeowners' repulsion or fear of these insects (Hickin, 1964; Olkowski et aI.,
1991; NW, personal observation).
Monitoring for thysanuran infestations requires detection of damage caused by insect feeding, detection of debris shed from insects (Jackson, 1886; Marlatt,
1915; Brett, 1962; Sweetman, 1965; Mallis, 1969, 1990), or capture of specimens on sticky cards or in jar traps placed in favourable thysanuran habitats
16 (Slabaugh, 1940; Mallis, 1969; Smith, 1970; Olkowski et aI., 1991; Tremblay &
Gries, 2003). Once a thysanuran infestation is detected, appropriate control measures should both eliminate the current infestation and prevent the return of future infestations. Elimination of infestations traditionally relied upon toxic baits
(Wakeland & Waters, 1931; Snipes et aI., 1936; Seiferle et aI., 1938; Richardson
& Seiferle, 1940; Wallace, 1942; Mallis, 1969) which more recently have been replaced by residual insecticides, antifeedants or repellents (Reviewed by
Tremblay, 2002). To prevent recurrence of an infestation, thysanuran-infested materials must not be allowed to enter the controlled area, and possible habitats should be made less desirable by lowering the relative humidity and reducing access to resources. This is typically accomplished by repairing water leaks, sealing cracks and crevices, increasing airflow and illumination, and removing all potential sources of food and shelter (Olkowski et aI., 1991; Tremblay, 2002;
Sioderbeck, 2004).
1.4 RESEARCH OBJECTIVES
Large knowledge gaps exist regarding communication among phylogenetically ancestral insects and related arthropods. Understanding the ecology of thysanurans and the mechanisms that mediate their aggregation behaviour would reveal much about the evolution of communication behaviour and physiology in terrestrial arthropods. This knowledge may also allow the
17 development of pheromone-based tactics for monitoring and control of thysanurans.
My research objectives in Chapters 2 and 3 were to test the hypotheses that:
(1) male, female and juvenile L. saccharina and C. longicaudata produce and
respond to an aggregation pheromone;
(2) behavioural response to pheromone requires physical contact;
(3) L. saccharina pheromone is derived from conspecific frass, scales, caudal
filaments or salivary secretions;
(4) pheromones of L. saccharina, C. longicaudata and T. domestica elicit a
behavioural response by closely related heterospecifics;
(5) T. domestica pheromone is derived from insect debris that is deposited within
shelters;
(6) T. domestica pheromone is derived from a particular type of frass;
(7) T. domestica pheromone is not derived from cellulose that previously has
been fed upon by conspecifics.
18 2 EVIDENCE FOR AN ARRESTMENT PHEROMONE IN L. SACCHARINA AND C. LONGICAUDATA *
2.1 INTRODUCTION
Most pheromones identified to date are low-molecular weight lepidopteran sex pheromones (Birch, 1974; Jurenka & Roelofs, 1993) that evolved to remain airborne and to mediate long-range attraction of mates for limited time
(Chapman, 1998). Pheromones that lack volatility are perceived when an insect contacts a substrate to which the pheromone adheres. Such contact pheromones occur in collembolans (Manica et aL, 2001), cockroaches (Nishida et aL, 1979;
Nojima et aL, 1999), termites (Henderson, 1998), locusts (McCaffery et aL,
1998), and thysanurans (Tremblay & Gries, 2003). Most of these insects inhabit enclosed microhabitats with little air movement, potentially rendering volatile pheromones less effective than contact pheromones. Moreover, many species that deploy contact pheromones for communication belong to phylogenetically ancestral taxonomic insect orders (Grimaldi & Engel, 2005). Identification of these chemicals will contribute to our understanding of the evolution of pheromone production (Roelofs et aL, 2002; Wertheim et aL, 2005).
•A very similar version of this chapter has been published: Woodbury and Gries (2007). Pheromone-based arrestment behavior in the common silverfish, Lepisma saccharina, and giant silverfish, Ctenolepisma longicaudata. Journal of Chemical Ecology 33: 1351-1358.
19 In this Chapter, I have studied pheromonal communication in three phylogenetically ancestral, synanthropic thysanurans, the common silverfish,
Lepisma saccharina L., giant silverfish, Ctenolepisma longicaudata Escherich, and the firebrat, Thermobia domestica (Packard). Male, female, and nymph T. domestica produce, and respond to an aggregation pheromone (Tremblay &
Gries, 2003) but require physical contact to perceive it. A similar communication system may exist in L. saccharina and C. longicaudata, as they also aggregate within human dwellings. Aggregating thysanurans maintain contact via antennae and caudal appendages (Tremblay, 2002; NW, personal observation), suggesting that the pheromone may be associated with these or other body parts, although one cannot discount salivary secretions as yet another potential source. All three species can be found in the same shelter (NW, personal observation) and thus may be able to recognize con- and heterospecific pheromones.
My objectives were to test the following hypotheses: 1) male, female and nymph
L. saccharina and C. longicaudata produce and respond to aggregation pheromones; 2) behavioural response to pheromone requires physical contact with the pheromone; 3) L. saccharina pheromone is present on or in frass, scales, antennae, caudal filaments or salivary secretions; and 4) pheromones of
L. saccharina, C. longicaudata, and T. domestica elicit a behavioural response by closely related heterospecifics.
20 2.2 MATERIALS AND METHODS
2.2.1 Collecting and Rearing of Experimental Insects
Thermobia domestica, C. longicaudata, and L. saccharina were collected by placing Petri dish (14 x 8 cm) traps baited with Quaker® oats on or around autoclaves and boilers at Simon Fraser University. Approximately 1,000 L. saccharina were also obtained from a laboratory colony at the University of
Sussex. Insects were maintained in glass rearing jars (10 x 12 cm) provisioned with a moist cotton wick, a Petri dish (3 x 1 cm) containing Quaker® oats, and a corrugated cone of filter paper (CCOFP) (Whatman® No.1, 125 mm diam) as a shelter. Each jar housed either 100 males, females or juveniles, or a mixed group
(100 insects total) of all stages. Jars were kept in a Plexiglas© container (30 x 22 x 22 cm) in contact with a heating rock (Zoo Med Labs Inc, San Luis Obispo, CA) so that the within-jar temperature ranged between 24-38°C depending on the proximity to the heat source. A within-jar relative humidity of 70-85% was maintained by leaving an open jar of water in contact with the heating rock. This range of humidity and temperature ensured optimal abiotic conditions for each of these species (Sweetman, 1938, 1939; Spencer, 1959). Insects were reared and tested under an 8L: 160 photoperiod (Sweetman, 1938, 1939) that provided ample time for nocturnal foraging and exploration of habitat prior to diurnal arrestment within shelters.
21 2.2.2 General Bioassay Procedures
Lepisma saccharina, T. domestica, and C. longicaudata naturally reside within confined spaces with little or no air movement (Spencer, 1930; Sweetman,
1938). Thus, still-air "olfactometers" were used for all experiments. They consisted of a central Pyrex® glass Petri dish connected to two lateral Petri dishes (each dish 9 x 3 cm) via glass tubing (2 x 2.5 cm) (Tremblay & Gries,
2003). Olfactometers were housed within opaque plastic bins (35 x 31 x 11 cm)
(Columbia Plastics Ltd. ®, Vancouver, B.C.), allowing diffuse but not directional light to enter. Each lateral chamber of an olfactometer received a filter paper
(Whatman® No.1, 125 mm diam) that was folded twice and formed into a cone, with the tip facing the central chamber. Cones served as shelters, ensuring that most insects were arrested in one of the lateral chambers during bioassays (NW, personal observation). For each replicate, an insect (previously isolated for 16 hr) was released into the central chamber 6 hr after the onset of scotophase, and a single observation of its position was recorded 16 hr later (2 hr prior to the start of scotophase). Each treatment and control cone was randomly assigned to one of the olfactometer's lateral chambers, and each replicate was run at 24 ± 2°C and
70-85% RH. Olfactometers were washed with hot water and Sparklene™ detergent, and were oven-dried at 125°C for 3 hr between each replicate.
22 2.2.3 Specific Experiments
In experiments 1-9 and 10-18, I tested the hypothesis that male, female and nymph L. saccharina and C. longicaudata each produces and responds to species-specific pheromone. The CCOFP (see above) was removed from rearing jars after three days of exposure to 100 insects, brushed off to remove insect derived frass and scales and then cut into eight equal pieces. A single piece was then inserted into the paper cone located within the treatment chamber of each olfactometer. The paper cone in the corresponding control chamber received a piece of CCOFP that had been removed from rearing jars containing oats and a moist wick, but no insects.
In experiments 19-20 and 21-22, I tested the hypothesis that female L. saccharina (experiments 19-20) and C. longicaudata (experiments 21-22) require physical contact to perceive and respond to their aggregation pheromone.
Considering that pheromone production and perception was neither gender- nor adult-specific in preceding experiments, this hypothesis was tested with females only. A CCOFP exposed for 3 days to a mixed group of male, female and nymph conspecifics (100 insects total) was placed so as to be accessible (see above) or inaccessible in the treatment chamber of an olfactometer. Inaccessible stimuli were suspended above a nylon mesh, stretched over the rim of the chamber and thus out of reach to test insects. Control stimuli from rearing jars containing only
23 oats and a moist wick were tested in a similar manner. One female L. saccharina or C. longicaudata was bioassayed in each replicate.
In experiments 23-26, I tested the hypothesis that L. saccharina aggregation pheromone is present on or in L. saccharina-derived frass (experiment 23), body scales (experiment 24), antennae or caudal filaments (experiment 25) or salivary gland secretions (experiment 26). The test stimuli were prepared from (i) dry fecal pellets (0.5 mg) recovered from female rearing jars after 3 days, (ii) scales
(0.5 mg) brushed off dorsal and ventral surfaces of 10 cold-anaesthetized females, (iii) four antennae and six caudal filaments removed from four cold anaesthetized females, or (iv) macerated salivary glands excised from three cold anaesthetized females. Each stimulus was spread within the paper cone shelter of a randomly assigned treatment chamber of an olfactometer. Paper cone shelters within the control chamber received no test stimulus. One female L. saccharina was bioassayed in each replicate.
In experiments 27-35, I tested the hypothesis that L. saccharina, C. longicaudata, and T. domestica respond to pheromones from con- and heterospecifics. Test stimuli consisted of a piece of CCOFP (see experiments 1-18) previously exposed to a mixed group of male, female, and juvenile insects. This was inserted into paper cones within the treatment chamber of each olfactometer.
Control chambers contained a piece of CCOFP from rearing jars containing only
24 oats and a moist wick. One female L. saccharina, C. longicaudata or T. domestica was bioassayed in each replicate.
2.2.4 Statistical Analyses
Numbers of insects responding to test stimuli in each experiment were analyzed by X2 tests, using JMpTM software (SAS®, Cary NC). The significance level was set at a::; 0.05. Insects found within the central chamber or connecting tunnels of olfactometers at termination of experiments were considered non-responders to either control or treatment papers, and therefore were not included in statistical analyses.
2.3 RESULTS
Male, female and juvenile L. saccharina all exhibited significant preference for arresting on a piece of CCOFP previously exposed to either male, female or juvenile conspecifics (Figure 2.1). Similar results were obtained with C. longicaudata (Figure 2.2). Female L. saccharina and C. longicaudata required physical contact with the pheromone to elicit arrestment (Figure 2.3). Neither insect-derived frass, body scales, antennae, caudal filaments or macerated salivary glands removed from females elicited significant arrestment responses
25 by female L. saccharina (Figure 2.4). Females of all species responded to conspecific pheromones, but varied in their response to those of heterospecifics.
Female C. longicaudata were arrested by both heterospecific pheromones, female L. saccharina by neither, and female T. domestica responded only to that from C. longicaudata (Figure 2.5).
26 Figure 2.1 Number of male, female, or juvenile L. saccharina responding to a
piece of filter paper previously exposed to male, female, or juvenile
L. saccharina. Numbers near bars indicate the number of insects
responding to the test stimulus. An asterisk (*) indicates a
significant preference for a particular test stimulus (l test; *P :::;
0.05, **P :::; 0.01). Numbers in brackets indicate numbers of non
responding insects.
27 00 ~~ Juveniles Exp. 1 Exp. 2 Exp. 3 oexposed paper 18** 25** 19**
control (0) (7) (6) Exp.4 Exp.S Exp. 6 ~ exposed 20** paper 19** 18**
control 0 (6) (0) (4) Exp. 7 Exp. 8 Exp.9 Juvenile exposed 27** 22** 20** paper
control (2) (1 ) (2) Test stimuli Number of L. saccharina responding
28 Figure 2.2 Number of male, female, or juvenile C. longicaudata responding to
a piece of filter paper previously exposed to male, female, or
juvenile C. longicaudata. Numbers near bars indicate the number of
insects responding to the test stimulus. An asterisk (*) indicates a
significant preference for a particular test stimulus (l test; *P ::;
0.05, **P ::; 0.01). Numbers in brackets indicate numbers of non
responding insects.
29 00 ~~ Juveniles Exp. 10 Exp. 11 Exp. 12 o exposed paper 20** 15** 16 **
control 0 (3) (3) (8) Exp. 14 Exp. 15 ¥exposed paper 20** 19**
control (0) (3) (3) Exp. 16 Exp. 17 Exp. 18 Juvenile exposed 13** 14* 18* paper
control (4) (1 ) (4) Test stimuli Number of C. longicaudata responding
30 Figure 2.3 Number of female L. saccharina (left) or C. longicaudata (right)
responding to a piece of filter paper previously exposed to male,
female, or juvenile conspecifics when stimulus contact was
prohibited or allowed. Numbers near bars indicate the number of
insects responding to the test stimulus. An asterisk (*) indicates a
significant preference for a particular test stimulus (l test; *P =:;
0.05, **P =:; 0.01). Numbers in brackets indicate numbers of non
responding insects.
31 Exp. 19 L"~",ri,, Exp.21 exposed paper CI~~~I'=exposed paper =:26 contact contact prohibited prohibited control 24 control 16 (10) (4) Exp. 20 Exp.22 L. saccharina ~ exposed paper 37** c.exposed""',,,"",.paper 28** contact contact allowed allowed control control 2 (4) (2) Test stimuli Number of L. saccharina responding Test stimuli Number of C. longicaudata responding
32 Figure 2.4 Number of female L. saccharina responding to conspecific frass,
scales, antennae and caudal filaments, or salivary gland contents.
Numbers near bars indicate the number of insects responding to
the test stimulus. An asterisk (*) indicates a significant preference
for a particular test stimulus (l test; *P S 0.05, **P S 0.01).
Numbers in brackets indicate numbers of non-responding insects.
33 Exp.23 Exp.25 Sf? frass 'i!aoleooae+ caudal 13 =:-20 filaments = control 12 control 17 (4) (6) Exp.24 Exp.26 Sf? scales 'i!salivarygland 26 =:20 contents =:- control 17 control 14 (8) (5) Test stimuli Number of L. saccharina responding Test stimuli Number of L. saccharina responding
34 Figure 2.5 Number of female L. saccharina, C. longicaudata, or T. domestica
responding to a piece of filter paper previously exposed to
conspecific or heterospecific males, females, and juveniles.
Numbers near bars indicate the number of insects responding to
the test stimulus. An asterisk (*) indicates a significant preference
for a particular test stimulus (X2 test; *P:::; 0.05, **P:::; 0.01).
Numbers in brackets indicate numbers of non-responding insects.
35 L. saccharina icaudata T domestica Exp.27 Exp.28 Exp.29 L saccharina exposed paper 20** 18 **
control (4) (7) (3) Exp.30 Exp. 31 Exp.32 c. longicaudata exposed paper 19 24** 17**
control (1 ) (8) Exp. 34 Exp.35 T. domestica exposed paper 15* 25**
control (4) (8) (0) Test stimuli Number of female insects responding
36 2.4 DISCUSSION
The arrestant type pheromone of T. domestica (Tremblay & Gries, 2003), L. saccharina and C. longicaudata (this study) may be particularly suitable for marking potential shelters that provide appropriate microclimatic conditions
(temperature, humidity), protection from predators, as well as access to food, water and potential mates. I argue that increases in population density and consequently pheromone deposition will expand the area of deposited pheromone and raise the concentration of pheromone at an aggregation site.
This may facilitate detection of suitable shelters, and may thus be correlated with the fitness of individual thysanurans. This correlation, an Allee effect (Stephens et aI., 1999), is believed to be the driving force behind the evolution of aggregation pheromone production (Wertheim et aI., 2005) and may also facilitate increased survival of T. domestica nymphs when they were reared in groups rather than in isolation (Sweetman, 1938).
Non-volatile insect pheromones identified thus far are discrete or complexed fatty acids (Naumann et aI., 1991; Finidori-Logli et aI., 1996; Kugimiya et aI., 2002), saccharides (Nojima et aI., 1999,2002) or steroids (Sakuma & Fukami, 1993b;
Kugimiya et aI., 2003). All of these pheromones are easily extracted with solvents of similar polarity to the pheromones themselves. My preliminary attempts to extract thysanuran pheromones with diverse polar and non-polar solvents have failed, suggesting that thysanuran pheromones may possess both polar and non-
37 polar segments that resist dissolution in any single solvent. Such amphipathicity would allow formation of micelles or polymerization, and adherence of the pheromone to solid substrates. Two amphipathic steroidal glucoside pheromones
(Blattellastanoside-A and -B) have been isolated from the German cockroach,
Blattella germanica (Sakuma & Fukami, 1993b). Similar to thysanuran pheromones, they are produced by males, females and nymphs, are perceived upon contact and elicit arrestment (Ishii & Kuwahara, 1967, 1968).
The non-volatile and non-labile nature of thysanuran pheromones is suitable as an aggregation and shelter marker. Such pheromones resist evaporation even at temperatures of 27-38°C, the range required by C. longicaudata and T. domestica (Adams, 1959; Spencer, 1959). Thus, the pheromone would not saturate the confined space typically inhabited by thysanurans nor cause adaptation and habituation of their olfactory system. Moreover, a non-polar or amphipathic pheromone does not readily dissolve in the polar environment of the humid microclimate (55-97% RH) thysanurans require to prevent desiccation
(Sweetman, 1938, 1939; Adams, 1959).
The aggregation pheromones of L. saccharina, C. longicaudata (Figures 2.1 and
2.2) and T. domestica (Tremblay & Gries, 2003) are produced by females, males and nymphs, suggesting they are present on or in materials that are common to nymphs and adults. However, none of the potential pheromone containing materials tested previously (Tremblay & Gries, 2003) or in this study (Figure 2.4)
38 elicited significant arrestment in any of these species. Frass and macerated salivary glands appear to have caused some arrestment responses (Figure 2.4) and ought to be investigated further, particularly in light of reports that the aggregation pheromone of European earwigs, Forficula auricularia L., is present in frass and shed cuticle (Walker et aI., 1993) or tibial glands (Sauphanor, 1992).
I also investigated the possibility that the arrestment behaviour was caused merely by insect-induced physical and chemical changes of the shelter, or food sources therein. However, I dismissed this possibility as glass surfaces exposed to insects for several days in the absence of food elicited strong arrestment by conspecifics (data not shown), clearly indicating that the insects deposit a signal.
Relatedness between C. longicaudata, T. domestica and L. saccharina can be investigated based on diverse criteria. Morphologically, C. longicaudata and T. domestica are more similar to each other than they are to L. saccharina.
Arrestment response by C. longicaudata, but not L. saccharina, to the T. domestica pheromone (Tremblay & Gries, 2003), and lack of arrestment response to heterospecific pheromone between T. domestica and L. saccharina
(this study; Figure 2.5), all support the concept that C. longicaudata and T. domestica are more closely related to each other than they are to L. saccharina
(Mendes, 1991). A definitive conclusion, however, must await analyses of all three species by molecular genetics. The fact that C. longicaudata females respond to both L. saccharina and T. domestica pheromone (Figure 2.5) is somewhat surprising but may be explained by the probability of co-inhabiting a
39 shelter with one of these heterospecifics. Lepisma saccharina and T. domestica prefer shelter temperatures between 21-2rC and 27-43°C, respectively
(Spencer, 1930, 1959; Sweetman, 1938, 1939), and by selecting such discrete temperature regimes they are effectively isolated. In contrast, C. longicaudata is readily found in shelters at temperatures between 17-30°C (Lindsay, 1940), overlapping those of both L. saccharina and T. domestica. Thus, C. longicaudata may frequently encounter suitable shelters of either L. saccharina or T. domestica and may have evolved the ability to recognize their respective pheromones.
40 3 SHELTER DEBRIS AND THE ARRESTMENT PHEROMONE OF T. DOMESTICA *
3.1 INTRODUCTION
Most aggregation pheromones produced by phylogenetically ancestral insects and related arthropods appear to be derived (at least in part) from frass. Frass or frass extract has been reported to induce aggregation in Collembola (Verhoef, 1984;
Manica et aI., 2001), Dermaptera (Walker et aI., 1993), Orthoptera (McFarlane et aI.,
1983), Acari (Leahy et aI., 1973; Otieno et aI., 1985; Dusbabek et aI., 1991;
Levinson et aI., 1991) and Blattodea (Ishii & Kuwahara, 1968; Scherkenbeck et aI.,
1999). Aggregations serve to mark suitable habitat or resources (McFarlane et aI.,
1983; Wileyto et aI., 1984; Rust &Appel, 1985; Sauphanor & Sureau, 1993; Walker et aI., 1993), reduce desiccation (Joosse, 1970; Joosse &Verhoef, 1974), increase encounters with mates or spermatophores (Sexton & Hess, 1968; Joosse, 1970;
Verhoef & Nagelkerke, 1977; Walker et aI., 1993) or foster contact between juveniles which promotes their growth and development (Ishii & Kuwahara, 1967; Takeda,
1980).
A very similar version of this Chapter has been accepted for publication: Woodbury and Gries (2008). Amber-colored excreta, a source of arrestment pheromone in firebrats, Thermobia domestica. Entomologia Experimentalis et Applicata (in press).
41 Thysanurans aggregate in response to abiotic cues (Tremblay & Gries, 2006) and pheromones (Tremblay &Gries, 2003; Woodbury &Gries, 2007; Chapter 2), possibly for similar reasons (see above) as described for other phylogenetically ancestral insects. Specifically, aggregation pheromone may help maintain close proximity between males and females, allowing females to readily encounter the reproductive threads and spermatophores that males deposit throughout the habitat
(Sweetman, 1938; Schaller, 1971; Sturm, 1987; Chapter 1). Pheromone-induced aggregations may also enhance predator vigilance. Aggregating thysanurans maintain close contact by resting their antennae and caudal appendages on or near conspecifics (Tremblay, 2002). Therefore, any threat that causes movement of an individual within that aggregation physically disrupts neighbouring insects and induces them to move as well. Finally, pheromone-induced aggregations of nymphs appear to promote their growth and development. Juvenile T. domestica reared in groups developed faster and lived longer than those reared in isolation (Sweetman,
1938).
Aggregation pheromones of thysanurans are non-volatile and arrest conspecifics on contact. They are produced and recognized by females, males and juveniles of L. saccharina, C. longicaudata (Woodbury & Gries, 2007; Chapter 2), and T. domestica
(Tremblay & Gries, 2003) but the source of the pheromone has not been determined. Female L. saccharina demonstrated a slight (but statistically not significant) preference for frass from conspecific shelters (Woodbury & Gries, 2007;
Chapter 2), a phenomenon warranting further investigation. Close examination of T.
42 domestica frass under a microscope (50 x total magnification) revealed that it consists of a mixture of three particle types contrasting in colour and texture (NW, personal observation) (see Figure 3.1). Similar frass types have been observed in various cockroach species (Cochran, 1973). Association of the pheromone with just one type of frass would facilitate its isolation and structural elucidation because its extraction would make use of a concentrated pheromone source. Other thysanuran derived debris accumulating in shelters include scales, shed exuviae, antennal and caudal filaments, saliva, hemolymph and fat body of injured or dead specimens fed on by conspecifics, and white immature and dark mature gametocysts (including sporocyst coils) from the gregarine parasite Lepismatophila thermobiae (Adams &
Travis) (Adams &Travis, 1935). Anyone of these debris types could be a source of the T. domestica aggregation pheromone.
Woodbury & Gries (2007) also investigated whether the arrestment behaviour of T. domestica might merely be caused by cellulose fed upon and thus altered by thysanurans. Although conceivable, this concept appears less likely because any other cellulose-feeding insect might cause similar alterations, rendering fed-on cellulose a signal not sufficiently specific for pheromonal communication. This conclusion is supported by findings that paper previously fed upon by termites induces aggregative feeding in conspecifics (Reinhard et aI., 2002) due not to alterations of cellulose but due to saliva (Kaib &Ziesmann, 1992; Reinhard et aI.,
1997; Reinhard & Kaib, 2001).
43 In Chapter 3, I test the hypotheses that (1) female T. domestica arrest in response to one or more conspecific-derived debris types; (2) a particular type of frass constitutes a source of the pheromone; and (3) fed-on cellulose is not the source of the arrestment signal.
3.2 MATERIALS AND METHODS
3.2.1 Collecting and Rearing of Experimental Insects
A T. domestica colony was established from insects captured at Simon Fraser
University, and at various apartment buildings in Vancouver, British Columbia. A colony of circa 2,000 insects was maintained within a Plexiglas® terrarium (30 x 22 x
22 cm) containing a moist cotton wick, a plastic Petri dish filled with Quaker® oats, and a centrally located heating rock (Zoo Med Labs, Inc., San Luis Obispo, CA,
USA). Six filter papers (Whatman® No.1, 125 mm diam) were each folded twice to form a cone and inserted between the heating rock and the edge of the terrarium with cone tips facing downward to serve as an insect shelter and to facilitate collection of insect-derived frass, exuviae and other debris. An open jar of water was left in contact with the heating rock to ensure a humidity range of 70-85% within the terrarium. Depending on proximity to the heating rock, terrarium temperatures ranged between 24° and 38°C. Insects were reared and bioassayed under an
8L:16D photoperiod. These conditions are within the range optimal for T. domestica development, survival and experimentation (Sweetman, 1938; Spencer 1959).
44 3.2.2 General Bioassay Procedures
Dual-choice olfactometers were used for all experiments to mimic the natural still-air habitat of T. domestica (Spencer, 1930; Sweetman, 1938). Olfactometers consisted of a central pyrex® glass Petri dish connected to two lateral Petri dishes (each dish 9 x 3 cm, and covered with a lid) via pyrex® glass tubing (2 x 2.5 cm) (Tremblay &
Gries, 2003; Woodbury & Gries, 2007; Chapter 2). Olfactometers were housed within opaque plastic bins (35 x 31 x 11 cm) (Columbia Plastics Ltd. ®, Vancouver
BC, CA), allowing diffuse but not directional light to enter. To mimic a natural shelter and ensure few non-responding individuals during bioassays (NW, personal observation), a filter paper (Whatman® No.1, 125 mm diam) was folded twice to form a cone and placed (tip facing the central chamber) into both lateral chambers of an olfactometer. Treatment stimuli were randomly placed within one of the lateral cones. Except for experiments 1 and 24-26, control cones remained empty or received the equivalent amount of solvent (experiments 18-23). For each replicate, a single insect was released into an olfactometer's central chamber 6 h after the onset of scotophase (lights off) and a single observation of its position was recorded 16 hr later (2 h before the onset of the next scotophase). Prior to experiments, insects were isolated for 16 h to prevent possible habituation to pheromone that might be present on the body surface of conspecifics or on substrates previously exposed to them. Assignment of treatment and control was random and all experiments were run at 25 ± 2°C and 70-85% rh, with the number of olfactometers deployed in
45 parallel dependant upon the availability of test stimuli. Olfactometers were washed with hot water and LiquiNox@ detergent, and were oven-dried at 1oooe for 3 h between each replicate.
3.2.3 Specific Experiments
In experiment 1, I retested whether female T. domestica arrest in response to filter paper previously exposed to female, male and juvenile conspecifics (Tremblay &
Gries, 2003). A filter paper cone that had served as a shelter for 150-200 colony insects was removed after 3-d exposure. Loose, insect-derived debris was brushed from the exposed paper using a paintbrush and collected for later bioassays. The brushed, exposed paper was cut into eight equal pieces and each piece was inserted into the paper cone located in the treatment chamber of an olfactometer.
The control chamber received a one-eighth piece of filter paper from rearing jars containing oats but no insects, and which had been kept within the colony terrarium at the same conditions for 3 d.
In experiment 2, I tested the hypothesis that female T. domestica arrest in response to loose, insect-derived debris that collects on insect-exposed filter paper. Debris
(500 ~g) that had been brushed from filter paper exposed to 150-200 colony insects for 3 days (see above) was brushed into the paper cone located in the treatment chamber of an olfactometer.
46 In experiments 3-8, I tested the hypothesis that female T. domestica arrest in response to one of six types of loose debris produced by conspecifics. Loose debris brushed from 3-d exposed colony papers was examined under a dissecting microscope at 50 x total magnification. Loose debris was classified, manually separated, and bioassayed as insect scales (experiment 3), shed exuviae (experiment 4), antennae and caudal filaments (experiment 5), white, immature gametocysts from the gregarine parasite Lepismatophila thermobiae
(experiment 6), dark, mature gametocysts including sporocyst coils from L. thermobiae (Adams &Travis, 1935) (experiment 7), and mixed frass (experiment
8). Of each debris type, 500 IJg were brushed into an olfactometer's treatment cone and pressed into the paper with the wide end of a pair of forceps to ensure that debris was distributed homogeneously from the cone tip to the outer perimeter of the paper.
In experiments 9-14, I tested the hypothesis that shed debris types (see experiments
3-8) that had been physically damaged by feeding conspecifics, or saliva, hemolymph or fat body from dead or injured specimens elicit arrestment by female
T. domestica. To replicate physical feeding damage, a watch glass and glass stir rod were used to macerate scales (experiment 9), exuviae (experiment 10), immature and mature L. thermobiae gametocysts and sporocysts (experiment 11), and mixed frass (experiment 12). Of each macerated debris type, 500 IJg were bioassayed in each replicate. For experiment 13, 4 cold-anaesthetized female T. domestica were placed dorsal side up inside an olfactometer's treatment cone and pressed lightly
47 with a microscope slide anteriorly to exude saliva but not fat body or hemolymph onto the paper. For experiment 14, 1 ml of hemolymph and fat body was removed from the abdomens of 80 cold-anaesthetized females. Using a 50-1J1 syringe, 5 drops
(20 IJI) of hemolymph and fat body were applied inside an olfactometer's treatment cone.
In experiments 15-23, I tested the hypothesis that female T. domestica arrest in response to one of 3 types of frass produced by conspecifics. Using a dissecting microscope (50 x total magnification), mixed frass (see experiment 8) brushed from paper exposed to 150-300 insects for 3 days was manually separated with fine forceps into 3 visibly distinct types: "amber", "white" and "reniform" frass. "Amber" frass particles are translucent, orange-, red- or brown-coloured, 300-600 IJm long and irregularly shaped, resembling polished amber. "White" frass particles are opaque, white- or tan-coloured, 500-1000 IJm long and coiled. "Reniform" frass particles are opaque, mottled grey to solid black, with a granulated texture, 500-100
IJm long and symmetrically ovoid or reniform in shape. Each type of frass (500 IJg per replicate) was brushed into a treatment paper cone without further treatment
(experiments 15-17), or was finely ground in a 2-ml conical vial in 1 ml of water
(experiments 18-20), or 1 ml of methanol (experiments 21-23) and pipetted into a treatment paper cone. Each type of frass was not soluble in non-polar solvents (NW, unpublished data) and sparingly soluble in polar solvents such as water or methanol.
Therefore, frass was extracted in polar solvent and the extract stirred to maintain a
48 suspension prior to bioassays. A 100-1.l1 frass/solvent suspension was applied in 10 droplets inside an olfactometer's treatment cone using a 1OO-~I syringe.
In experiments 24-25, I tested the hypothesis that female T. domestica arrest in response to filter paper cellulose that had been physically or chemically altered by feeding insects. For both experiments, a conical paper shelter previously exposed to
T. domestica (see experiment 1) was cut in half to separate the cone tip where most frass and debris had collected from the outer perimeter where the most feeding damage had occurred. In each replicate, a one-eighth piece of either cone tip paper
(experiment 24) or outer perimeter paper (experiment 25) was tested. Equally sized pieces of paper that had not been exposed to insects served as controls. In experiment 26, I tested whether the arrestment pheromone is produced or deposited in the absence of a cellulose food source. A mixed group (20 insects total) of females, males and juveniles was left in contact for 3 days with the convex side of a watch glass (5 cm diam) in a capped Petri dish of similar diameter to ensure contact of insects with the glass. A watch glass that had not been exposed to insects served as a control.
In experiments 27 and 28, I tested the hypothesis that female T. domestica arrest in response to male-produced silk. For each replicate in experiment 27, a 3-cm long bundle of silk, removed from insect-exposed shelter papers (see experiment 1), was placed inside an olfactometer's treatment paper cone. For each replicate in experiment 28, three 1-cm long bundles of silk were collected on glass by gently
49 squeezing the abdomens of 1-5 cold anaesthetized males posteriorly between 2 microscope slides. This silk was then rubbed inside an olfactometer's treatment cone. Both old and freshly squeezed silk were tested to account for potential chemical, physical or visual changes that aging silk may undergo, and that might arrest conspecifics.
3.2.4 Statistical Analyses
Numbers of insects responding to test stimuli in each experiment were analyzed by l test with Yate's correction for 1 dJ., using JMpTM software (SAS®, Cary NC, USA).
The significance level was set at a :::; 0.05. Any insect not contacting a shelter cone in an olfactometer's lateral chamber was considered a non-responder and not included in statistical analyses.
3.3 RESULTS
Filter paper previously exposed to conspecifics elicited significant arrestment from female T. domestica (Figure 3.1, experiment 1), as did loose, insect-derived debris
(experiment 2) and mixed frass (experiment 8). In contrast, shed scales, exuviae, antennae, caudal filaments and cysts of the parasite L. thermobiae elicited no significant behavioural response (experiments 3-7). Similarly, neither macerated scales, mixed frass, cysts of L. thermobiae (experiments 9-12), nor saliva
50 (experiment 13) had behavioural activity. Hemolymph and fat body were significantly deterrent (experiment 14). Of dry amber, white and reniform frass, only the first elicited significant arrestment when not exposed to solvent (experiments 15, 16, 17).
Indeed, white frass was significantly deterrent (experiment 16). Neither water nor methanol suspensions of amber or reniform frass were behaviourally active
(experiments 18, 20, 21, 23). A suspension of macerated white frass in methanol, but not in water, elicited significant arrestment (experiments 19, 22). The tip of filter paper cone shelters (where frass and debris had accumulated) arrested females
(experiment 24), whereas the perimeter of such shelters (where heavy feeding had occurred) did not (experiment 25). Glass surfaces exposed to T. domestica for several days arrested conspecific females (experiment 26), whereas silk retrieved from insect-exposed shelters (experiment 27) or squeezed from live insects
(experiment 28) did not.
51 Figure 3.1 Number of female T. domestica (A) responding to shelter paper
exposed to conspecifics for 3 days (experiment 1) or insect-derived
debris accumulating in those shelters; and (8) responding to insect
exposed paper shelter tips, paper shelter perimeters, glass
surfaces exposed to conspecifcs for 3 days, silk removed from
shelters, or silk squeezed from male T. domestica. Control papers
and glass were not exposed to conspecifics and did not contain
insect-derived debris. Numbers within brackets indicate the number
of insects responding to the test stimulus (left number) or control
(right number). Subscript numbers outside of brackets indicate
numbers of non-responding insects. An asterisk (*) indicates a
significant preference for a particular test stimulus (l test; *P s;
0.05, **P s; 0.01).
52 Exp. 3 (A) scales (24:20), ~ Exp. 15 Exp.4 amber frass (31'15)* exuviae (9: 12)3 (dry) . 6
Exp.5 - antennae + Exp. 18 immature filaments (17:20)2 am.ber frass (26: 17) gametocyst (In H20) 0 Exp.6 amber immature (12:12), f---- Exp.21 gametocysts frass amber frass (2333) (in MeOH) . 7 Exp. 7 mature (14:13), gametocysts f-- Exp. 16 white frass (10'22)* Exp. 8 (26:12)~ (dry) . 2 mixed frass mature gametocyst f---- Exp. 19 & sporocysts Exp. 9 white frass (13'21) macerated (in H20) . 5 scales (9: 10h - Exp.22 white Exp. 10 white frass (29'13)* macerated (in MeOH) . 3 frass exuviae (10: 16h Exp. 1 shelter(76'21 )** Exp.11 - Exp. 17 paper . 6 macerated (20: 16)6 reniform frass(19'22) gametocysts (dry) . 3
Exp. 12 - Exp.20 Exp.2 macerated (12: 15) reniform frass mixed frass 4 (10:18)3 shelter (42:21 )** (inHp) debris 5 Exp. 13 saliva (24:28h - Exp.23 reniform reniform frass(14'17) frass Exp. 14 (in MeOH) ., hemolymph + fat body(13:34)~*
(8) Exp.24 Exp. 25 Exp.26 Exp.27 Exp.28 shelter (18:6)* shelter (10:9) exposed (39:7)* shelter (12'10) squeezed (20'17) tip 1 perimeter 3 glass , silk . 2 silk . 0
53 3.4 DISCUSSION
Significant arrestment of bioassayed insects caused by mixed frass (experiment 8) but not by other debris types (experiments 3-7) suggests that the arrestment induced by loose insect-derived debris (experiment 2) is due only to frass within that debris.
Of the three frass types, only amber frass in its natural dry state arrested female T. domestica (experiments 15-17) leading me to conclude that amber frass is the single constituent of loose debris responsible for eliciting arrestment (experiment 2). That a methanol suspension of macerated white frass (experiment 22), unlike dry white frass (experiment 16), arrested females may have been due to small quantities of amber frass or some other arrestant components that are typically embedded in white frass and that may have been liberated during maceration in methanol. The fact that mixed frass caused no or only weak arrestment of female T. domestica in a previous study (Tremblay & Gries, 2003) could have been due to the different relative proportions of the three frass types, with the deterrent white frass
(experiment 16) possibly more prevalent in the preceding studies. The cockroach
Shawella couloniana (Saussure) also produces three types of frass (Cochran, 1973) which resemble those of T. domestica. The white but not the amber or reniform frass type of S. couloniana contains a high percentage of uric acid, formed from malphigian tubule wastes and passed to the rectum as a means of eliminating nitrogen from a nitrogen-rich diet (Cochran, 1973). Thermobia domestica also consume a stable, nitrogen-rich diet (Tremblay, 2002) and microscopic inspection of
its white frass reveals ridges that may mirror those of the rectal pads (NW, personal
54 observation). Despite the similarities between the multiple frass types of T.
domestica and S. couloniana, the chemical constituents of T. domestica frass are yet to be determined as are the types of frass produced by other thysanuran
species.
Filter paper previously exposed to conspecifics (experiment 1) appears to be even
more strongly arrestant to female T. domestica than loose insect-derived debris
(experiment 2), suggesting that the paper retained some components of the
arrestment pheromone that are not present in mixed debris. Alternatively, the
process of transferring loose debris to olfactometers could have adversely altered
the ratio and/or physical distribution of debris components, resulting in reduced
biological activity. In humid microclimates, amber type frass adheres to substrates
much more strongly than other frass types which readily fall away from vertical
surfaces of the shelter (NW, personal observation). Conceivably, both adhesion of
amber type frass and its separation from other frass types are required for T.
domestica arrestment. This might explain why shelter papers with only amber frass
adhering to it appeared more strongly arrestant (experiment 1) than loose and mixed
shelter debris (experiment 2) or mixed frass (experiment 8) pressed against and
adhering to shelter paper. Moreover, portions of white frass break into a crystalline
powder when pressed or macerated. This fine powder may adhere to the antennae
of T. domestica and thus interfere with their ability to detect amber frass present in
debris and frass mixtures used for experiments 2 and 8. This adherent powder may
also have contributed to the significant repellency of dry white frass (experiment 16).
55 The strong arrestment response induced by T. domestica-exposed shelters
(Tremblay & Gries, 2003, Woodbury & Gries, 2007; this study, experiment 1) could also have been due to physical damage to paper caused by mandibular tearing or due to chemical alterations to cellulose caused by endogenous cellulase (Zinkler &
G6tze, 1987; Treves & Martin, 1994). However, the arrestment activity of insect exposed glass (experiment 26) eliminates cellulose in natural or altered states as the source that triggered arrestment of females. Moreover, cone tips of exposed paper shelters (where most frass and debris had collected) arrested females, whereas the outer perimeter of paper shelters (where cellulose consumption and damage were most prevalent) did not (experiments 24-25). Although pellets of amber frass were less abundant on insect-exposed glass (experiment 26) than on exposed papers, amber frass in small quantities was visible and likely was also present as surface residue. These results support our conclusion that arrestment is elicited, in part, by amber frass associated with insect debris (see experiment 15) rather than insect altered cellulose.
Silk filaments produced by male T. domestica during mating serve to arrest females near spermatophores (Sturm, 1987; Dallai, 1989), but are not a source of the contact aggregation pheromone that arrests female, male and nymph conspecifics. Neither silk removed from shelters (experiment 27) nor silk squeezed from males
(experiment 28) arrested females. These results suggest that silk may be more a
physical barrier than a chemical arrestant, or that it is a chemical arrestant only
56 during times of mating. Considering that the T. domestica arrestment pheromone is produced by females, males and juveniles (Tremblay & Gries, 2003), it is not surprising that silk, which is produced exclusively by males, did not result in arrestment.
Hemolymph and fat body as other potential sources of arrestment pheromone were deterrent. However, they temporarily arrested all bioassayed insects at first contact
(NW, personal observation). The omnivorous diet of T. domestica requires carbohydrates, proteins and lipids (Sweetman, 1938; 1939; Wall & Swift, 1954).
Protein- and lipid-starved insects likely obtain these nutrients from the hemolymph and fat body of dead or injured hetero- and conspecific insects (Sweetman, 1939).
The aging resource may then generate necromones (Rollo et aI., 1994) that are known to cause avoidance responses from other groups of insects. The initial
"attractiveness" of hemolymph and fat body may also explain why excised salivary glands that possess trace quantities of hemolymph and fat body were somewhat arrestant (Woodbury & Gries, 2007), whereas squeezed saliva was not (experiment
13).
Shed insect-derived debris, such as scales, exuviae, as well as antennal and caudal filaments could also have been a source of the arrestment pheromone. The whole insect body surface or specific body parts are sources of short-range or contact
pheromones (Tregenza & Wedell, 1997; Schlamp et aI., 2005) and scale-derived semiochemicals also mediate interspecific communication. For example, ovipositing
57 female codling moth, Cydia pomonella (L.), inadvertently deposit abdominal scales with their eggs which then become sources of kairomones that attract the egg parasitoid, Ascogasterquadridentata Wesmael (DeLury et aI., 1999). However, except for frass, shed insect-derived debris contains no T. domestica arrestment pheromone (experiments 3-12).
Cysts of the parasite L. thermobiae were bioassayed because insect symbionts are known to contribute to communication or exploitation of resources for some insects.
For example, fungi associated with bark beetles manipulate the beetles to act as a fungal vector (McLeod et aI., 2005), and bacteria associated with house fly eggs act to both induce and inhibit oviposition by other flies (Lam et aI., 2007). However, if T. domestica were to rely on the presence of the parasite L. thermobiae for pheromonal communication, then non-parasitized specimens would be unable to communicate.
Moreover, L. thermobiae infests many species of thysanura (Lindsay, 1939; Crusz,
1957, 1960; Haldar & Chakraborty, 1977; Clopton, 2002) of which some are not responsive to heterospecific pheromones (Tremblay & Gries, 2003, Woodbury &
Gries, 2007), thus rendering the parasite L. thermobiae an unlikely pheromone source.
Thysanurans consume lichens, fungi, yeasts, pollen, and decaying plant and animal tissues (Tremblay, 2002). The presence and proportion of these dietary constituents, and the resulting frass, likely differ between species as a result of contrasting abiotic and biotic conditions of their preferred habitat. This would
58 explain arrestment of T. domestica in response to the pheromone of the giant silverfish, Ctenolepisma longicaudata, but not to that of the common silverfish,
Lepisma saccharina (Woodbury &Gries, 2007). Moreover, frass production is limited to well-nourished insects, and frass accumulates in only those shelters that contain aggregating live insects, thus marking safe refugia. When cemented to shelter surfaces (see experiment 26), frass also ensures some permanency of the pheromonal signal.
59 4 CONCLUSION
In my thesis, I have investigated pheromonal communication in three synanthropic thysanuran species: L. saccharina, C. longicaudata and T. domestica. Based on my data, the following conclusions can be drawn:
1. Male, female and juvenile L. saccharina and C. longicaudata each produce
and perceive an aggregation pheromone that elicits arrestment behaviour in
the receiver.
2. Arrestment of female L. saccharina and C. longicaudata requires physical
contact with the pheromone source, suggesting that both pheromones are non
volatile.
3. Lepisma saccharina does not respond to the pheromones of C. longicaudata
or T. domestica, C. longicaudata responds to the pheromones of L. saccharina
and T. domestica, and T. domestica responds to the pheromone of C.
longicaudata, but not that of L. saccharina.
4. The arrestment pheromone of T. domestica is derived, at least in part, from
conspecific, amber-type frass that is deposited within insect shelters.
5. Cellulose that has been altered via previous feeding upon by T. domestica,
does not elicit arrestment in conspecific females.
60 REFERENCES
Adams JA (1933a) Biological notes upon the firebrat, Thermobia domestica
Packard. Journal of the New York Entomological Society 41: 557-562.
Adams JA (1933b) The early instars of the firebrat, Thermobia domestica
(Packard), (Thysanura). Iowa Academy of Science 40: 217-219.
Adams JA (1959) Methods of rearing Lepismatids. Culture Methods for
Invertebrate Animals, pp. 261-263, Dover Publications, New York, NY, USA.
Adams JA &Travis BV (1935) Two new species of gregarine protozoa from the
firebrat, Thermobia domestica (Pack.) (Thysanura). Journal of Parasitology 21:
56-59.
Arnett RH (1985) Thysanura (silverfish and allies). American Insects: A
Handbook of the Insects of America North of Mexico, pp. 80-81. Van
Nostrand Reinhold, New York, NY, USA.
Austin J & Richardson CH (1941) Ability of the firebrat to damage fabrics and
paper. Journal of the New York Entomological Society 49: 357-365.
Bell WJ, Burk T& Sams GR (1973) Cockroach aggregation pheromone:
directional orientation. Behavioral Biology 9: 251-255.
Bell WJ, Parsons C & Martinko EA (1972) Journal of the Kansas Entomological
Society 45: 414-421.
Berger BG (1945) Food preferences of the firebrat. Journal of Economic
Entomology 38: 577-582.
61 Birch MC (1974) Pheromones. Elsevier, New York, NY, USA.
Bitsch J (1990) Ultrastucture of the phallic glands of the firebrat, Thermobia
domestica (Packard) (Thysanura: Lepismatidae). International Journal of
Insect Morphology and Embryology 19: 65-78.
Block EF & Bell WJ (1974) Ethometric analysis of cockroach receptor function.
Journal of Insect Physiology 20: 993-1003.
Borden JH (1985) Aggregation pheromones. Comprehensive Insect Physiology,
Biochemistry, and Pharmacology, Vol. 9 (ed. by GA Kerkut & LI Gilbert), pp.
257-285. Pergamon Press, Oxford.
Brett CH (1962) Thysanurans: Damage by and control of silverfish and firebrats.
Pest Control 30: 75-78.
Brossut R (1979) Gregarism in cockroaches and in Eublaberus in particular.
Chemical Ecology: Odour Communication in Animals (ed. by FJ Ritter), pp.
237-246. Elsevier/North Holland Biomedical Press, New York, NY, USA.
Brossut R, Dubois P& Regaud J (1974) Le gregarisme chez Blaberus craniifer.
Isolement et identification de la pheromone. Journal of Insect Physiology 20:
529-543.
Buck C & Edwards JS (1990) The effect of appendage and scale loss on instar
duration in adult firebrats, Thermobia domestica (Thysanura). Journal of
Experimental Biology 151: 341-347.
Carapelli A, Frati F, Nardi F, Dallai R & Simon C (2000) Molecular phylogeny of
the apterygotan insects based on nuclear and mitochondrial genes.
Pedobiologia 44: 361-373.
62 Chapman RF (1998) The Insects: Structure and Function. Cambridge University
Press, New York, NY, USA.
Clopton RE (2002) Phylum Apicomplexa Levine, 1970: Order Eugregarinorida
Leger, 1900. Illustrated Guide to the Protozoa, 2nd Edition (ed. by JJ Lee, D
Patterson & PC Bradbury), pp. 205-288. Society of Protozoologists, Lawrence,
KS, USA.
Cochran DG (1973) Comparative analysis of excreta from twenty cockroach species.
Comparative Biochemistry and Physiology 46: 409-419.
Crampton GC (1916) The phylogenetic origin and the nature of the wings of
insects according to the paranotal theory. Journal of the New York
Entomological Society 24: 1-39.
Crusz H (1957) Gregarine protozoa of silverfish (Insecta: Thysanura) from Ceylon
and England, with the recognition of a new genus. Journal of Parasitology 43: 90
92.
Crusz H (1960) New gregarines parasitic in Lepismatids from Ceylon. Proceedings
of the Zoological Society of London 135: 525-536.
Curran CH (1946) Insects in the house: silverfish. Natural History 55: 391.
Dahm KH, Meyer D, Finn WE, Reinhold V& Roller H (1971) The olfactory and
auditory mediated sex attraction in Achroia grisella (Fabr.).
Naturwissenschaften 58: 265-266.
Dallai R (1989) Structure and function of the male genital organs and spermatophore
formation in Thermobia domestica (Lepismatidae, Zygentoma, Insecta). 3rd
63 International Seminar on Apterygota. Siena, Italy, August 21-26,1989 (ed. by R
Dallai), pp. 245-252. University of Sienna, Sienna, Italy.
Delany MJ (1959) Group formation in the Thysanura. Animal Behavior 7: 70-75.
DeLury NC, Gries R, Gries G, Judd GJR & Khaskin G (1999) Moth scale-derived
kairomones used by egg-larval parasitoid Ascogaster quadridentata to locate
eggs of its host, Cydia pomonella. Journal of Chemical Ecology 25: 2419-2431.
Dethier VG, Barton Browne L & Smith CN (1960) The designation of chemicals in
terms of the responses they elicit from insects. Journal of Economic
Entomology 53: 134-136.
Dillon RJ, Vennard CT & Charnley AK (2000) Exploitation of gut bacteria in the
locust. Nature 403: 851.
Dillon RJ, Vennard CT & Charnley AK (2002) A note: gut bacteria produce
components of a locust cohesion pheromone. Journal of Applied Microbiology
92: 759-763.
Dusbabek F, Simek P, Jegorov A & Triska J (1991) Identification of xanthine and
hypoxanthine as components of assembly pheromone in excreta of argasid ticks.
Experimental and Applied Acarology 11: 307-316.
Edwards JS & Reddy GR (1986) Mechanosensory appendages and giant
interneurons in the firebrat (Thermobia domestica, Thysanura): a prototype
system for terrestrial predator evasion. The Journal of Comparative
Neurobiology 243: 535-546.
Ferguson LM (1990) Insecta: Microcoryphia and Thysanura. Soil Biology Guide
(ed. by DL Dindal), pp. 935-949. John Wiley & Sons Inc., NY, USA.
64 Finidori-Logli VM, Bagneres AGM, Erdmann OM, Francke WM & Clement JL
(1996) Sex recognition in Diglyphus isaea Walker (Hymenoptera:
Eulophidae): role of an uncommon family of behaviourally active compounds.
Journal of Chemical Ecology 22: 2063-2079.
Fuzeau-Braesch S, Genin E, Jullien R, Knowles E & Papin C (1988) Composition
and role of volatile substances in atmosphere surrounding two gregarious
locusts, Locusta migratoria and Schistocerca gregaria. Journal of Chemical
Ecology 14: 1023-1 033.
Gillett SO, Packham JM & Papworth SJ (1976) Possible pheromonal effects on
aggregation and dispersion in the desert locust, Schistocerca gregaria
(Forsk.). Acrida 4: 287-298.
Gray B (1974) Associated fauna found in nests of Myrmecia (Hymenoptera:
Formicidae). Insectes Sociaux 21: 289-300.
Grimaldi 0 & Engel MS (2005) Evolution of the Insects. Cambridge University
Press, New York, NY, USA.
Haldar DP & Chakraborty N (1977) Observations on the cephaline gregarine,
Lepismatophila rhombocephala n. sp. (Protozoa: Sporozoa) from silver fish.
Archiv fOr Protistenkunde 119: 361-366.
Hart M (2006) The role of sonic signals in the sexual communication of peach twig
borers, Anarsia lineatella, Zeller (Lepidoptera, Gelechiidae). MSc Thesis, Simon
Fraser University, Burnaby, BC, Canada.
Henderson G (1998) Primer pheromones and the possible caste influence on the
evolution of sociality in lower termites. Pheromone Communication in Social
65 Insects: Ants, Wasps, Bees, and Termites (ed. by RK Vander Meer, MD
Breed, ML Winston & K Espelie), pp. 314-330. Westview Press, Boulder, CO,
USA.
Hickin NE (1964) Silverfish and Springtails. Household Insect Pests, pp. 43-46.
Hutchinson & Co. Ltd., London.
Ishii S (1970) An aggregation pheromone of the German cockroach, B1attella
germanica (L.) 2. Species specificity of the pheromone. Applied Entomology
and Zoology 5: 33-41.
Ishii S& Kuwahara Y (1967) An aggregation pheromone of the German
cockroach Blattella germanica L. (Orthoptera: Blattellidae) I. Site of the
pheromone production. Applied Entomology and Zoology 2: 203-217.
Ishii S& Kuwahara Y (1968) Aggregation of German cockroach (Blattella
germanica) nymphs. Experientia 24: 88-89.
Jackson RT (1886) A new museum pest. Science 7: 481-483.
Joosse ENG (1970) The formation and biological significance of aggregations in
the distribution of Collembola. Netherlands Journal of Zoology 20: 299-314.
Joosse ENG & Koelman TACM (1979) Evidence for the presence of aggregation
pheromones in Onychiurus armatus (Collembola), a pest insect in sugar beet.
Entomologia Experimentalis et Applicata 26: 197-201.
Joosse ENG &Verhoef HA (1974) On the aggregational habits of surface dwelling
Collembola. Pedobiologia 14: 245-249.
Jurenka RA & Roelofs WL (1993) Biosynthesis and endocrine regulation offatty
acid derived sex pheromones in moths. Insect Lipids: Chemistry,
66 Biochemistry, and Biology (ed. by DW Stanley Samuelson & DR Nelson), pp.
353-388. University of Nebraska Press, Lincoln, NE, USA.
Kaib M& Ziesmann J (1992) The labial gland in the termite Schedorhinotermes
lamanianus (Isoptera: Rhinotermitidae): morphology and function during
communal food exploitation. Insectes Sociaux 39: 373-384.
Kristensen NP (1981) Phylogeny of insect orders. Annual Review of Entomology
26: 135-157.
Kugimiya S, Nishida R, Kuwahara Y & Sakuma M (2002) Phospholipid
composition and pheromonal activity of nuptial secretion of the male German
cockroach, Blattella germanica. Entomologia Experimentalis et Applicata 104:
337-344.
Kugimiya S, Nishida R, Sakuma M & Kuwahara Y (2003) Nutritional
phagostimulants function as male courtship pheromone in the German
cockroach, Blattella germanica. Chemoecology 13: 169-175.
Kukalova-Peck J (1986) New carboniferous Diplura, Monura, and Thysanura, the
hexapod ground plan, and the new role of thoracic side lobes in the origin of
wings (Insecta). Canadian Journal of Zoology 65: 2327-2345.
Labandeira CC, Beall BS & Hueber FM (1988) Early insect diversification:
evidence from a lower devonian bristletail from Quebec. Science 242: 913
916.
Lam K, Babor D, Duthie B, Babor EM, Moore M & Gries G (2007) Proliferating
bacterial symbionts on house fly eggs affect oviposition behaviour of adult flies.
Journal of Animal Behaviour 74: 81-92.
67 Leahy MG, Vandehey R & Galun R (1973) Assembly pheromone(s) in the soft tick
Argas persicus (Oken). Nature 246: 284-517.
Leonard MA & Bradbury PC (1984) Aggregative behaviour in Foisomia candida
(Collembola: Isotomidae), with respect to previous conditioning. Pedobiologia
26: 369-372.
Levinson HZ, Levinson AR & Muller K (1991) Functional adaptation of two
nitrogenous waste products in evoking attraction and aggregation of flour mites
(Acarus sire L.). Journal of Pest Science 64: 55-60.
Lindsay E (1939) Two gregarines from Ctenolepisma longicaudata, with notes on
forms in other silver fish. Proceedings of the Royal Society of Victoria 51: 99-111.
Lindsay E (1940) The biology of the silverfish, Ctenolepisma longicaudata Esch.
with particular reference to its feeding habits. Proceedings of the Royal
Society of Victoria 52: 35-83.
Lubbock J (1873) Monograph of the Collembola and Thysanura. Ray Society,
London.
Mallis A (1941) Preliminary experiments on the silverfish, Ctenolepisma urbani
Slabaugh. Journal of Economic Entomology 34: 787-791.
Mallis A (1969) Silverfish. Handbook of Pest Control, pp. 119-135. MacNair
Dorland, New York, NY, USA.
Mallis A (1990) Silverfish and booklice, revised by Richard V. Carr. Handbook of
Pest Control: The Behavior, Life History and Control of Household Pests, pp.
87-92. Franzak & Foster Co., Cleveland, Ohio, USA.
68 Mallis A, Miller AC & Hill RC (1958) Feeding of four species of fabric pests on
natural and synthetic textiles. Journal of Economic Entomology 51: 248-249.
Manica A, McMeechan K &FosterWA (2001) An aggregation pheromone in the
intertidal collembolan Anurida maritima. Entomologia Experimentalis et
Applicata 99: 393-395.
Marlatt CL (1915) The silverfish: an injurious household insect. U.S. Department
of Agriculture, Farmer's Bulletin 681: 1-4.
Mayer MS & McLaughlin JR (1991) Handbook of Insect Pheromones and Sex
Attractants. CRC, Boca Raton, Florida, USA.
McCaffery AR, Simpson SJ, Islam MS & Roessingh P (1998) A gregarizing factor
present in the egg pod foam of the desert locust Schistocerca gregaria.
Journal of Experimental Biology 201: 347-363.
McFarlane JE & Alii I (1986) Aggregation of larvae of Blattella germanica (L.) by
lactic acid present in excreta. Journal of Chemical Ecology 12: 1369-1375.
McFarlane JE, Steeves E &Alii I (1983) Aggregation of larvae of the house
cricket, Acheta domesticus (L.), by propionic acid present in the excreta.
Journal of Chemical Ecology 9: 1307-1315.
McLeod G, Gries R, von Reu~ SH, Rahe JEt Mcintosh R, Konig WA & Gries G
(2005) The pathogen causing Dutch elm disease makes host trees attract insect
vectors. Proceedings of the Royal Society B 272: 2499-2503.
Mendes LF (1982) On a collection of Lepismatidae from the new world with
description of a new species (Zygentoma). Entomologica Scandinavica 13:
97-102.
69 Mendes LF (1991) On the phylogeny of the genera of Lepismatidae (Insecta:
Zygentoma). Advances in Management and Conservation of Soil Fauna (ed.
by GK Veeresh, 0 Rajagopal & CA Viraktamath), pp. 3-13. Oxford & ISH
Publishing, New Delhi.
Metzger VR & Trier KH (1975) Zur Bedeutung der Aggregationspheromone von
B/attella germanica und B/atta orienta/is. Angewandte Parasitologie 16: 16
27.
Meyer AE (1932) Ober Helligkeitsreaktionen von Lepisma saccharina L.
Zeitschrift fOr Wissenschaftliche Zoologie 142: 254-312.
Mori K & Fukamatsu K (1993) Synthesis of blattellastanoside A, a steroid
glucoside isolated as the aggregation pheromone of the German cockroach.
Proceedings of the Japan Academy B 69: 61-64.
Naumann K, Winston ML, Slessor KN, Prestwich GO & Webster FX (1991).
Production and transmission of honey bee queen (Apis mellifera L.)
mandibular gland pheromone. Behavioral Ecology and Sociobiology 29: 321
332.
Nishida R, Sato T, Kuwahara Y, Fukami H & Ishii S (1979) Female sex
pheromone of the German cockroach, Blattella germanica (L.) (Orthoptera:
Blattellidae), responsible for male wing-raising II. 29-Hydroxy-3,11-dimethyl-2
nonacosanone. Journal of Chemical Ecology 2: 449-455.
Nojima S, Kugimiya S, Nishida R, Sakuma M& Kuwahara Y (2002)
Oligosaccharide composition and pheromonal activity of male tergal gland
70 secretions of the German cockroach, Blattella germanica (L.). Journal of
Chemical Ecology 28: 1483-1494.
Nojima S, Nishida R, Kuwahara Y & Sakuma M (1999) Nuptial feeding
stimulants: a male courtship pheromone of the German cockroach, B1aftella
germanica (L.) (Dictyoptera: Blattellidae). Naturwissenschaften 86: 193-196.
Obeng-Ofori 0, Torto B, Hassanali A (1993) Evidence for mediation of two
releaser pheromones in the aggregation behavior of the gregarious desert
locust, Schistocerca gregaria (Forskal) (Orthoptera: Acrididae). Journal of
Chemical Ecology 19: 1665-1676.
Obeng-Ofori 0, Njagi PGN, Torto B, Hasanali A &Amiani H (1994a) Sex
differentiation studies relating to releaser aggregation pheromones of the
desert locust, Schistocerca gregaria. Entomologia Experimentalis et Applicata
73: 85-91.
Obeng-Ofori 0, Torto B, Njagi PGN, Hassanali A& Amiani H (1994b) Fecal
volatiles as part of the aggregation pheromone complex of the desert locust,
Schistocerca gregaria (Forskal) (Orthoptera: Acrididae). Journal of Chemical
Ecology 20: 2077-2087.
Olkowski W, Daar S& Olkowski H (1991) Common-Sense Pest Control, pp. 209
214. Taunton Press Inc., Newtown, CT, USA.
Otieno DA, Hassanali A, Obenchain FD, Sternberg A & Galun R (1985) Identification
of guanine as an assembly pheromone of ticks. Insect Science and its
Applications 6: 667-670.
71 Powell JA & Hogue CL (1979) Silverfish and bristletails. California Insects, pp.
38-41. University of California Press, Berkeley, CA, USA.
Proctor HC (1998) Indirect sperm transfer in arthropods: behavioural and
evolutionary trends. Annual Review of Entomology 43: 153-174.
Reeve DH & Berry RE (1976) Evidence for an arrestant causing aggregation in
the garden symphylan. Environmental Entomology 5: 961-963.
Reinhard J, Hertel H & Kaib M (1997) Feeding stimulating signal in labial gland
secretion of the subterranean termite Reticulitermes santonensis. Journal of
Chemical Ecology 23: 2371-2381.
Reinhard J& Kaib M (1995) Interaction of pheromones during food exploitation
by the termite Schedorhinotermes lamanianus. Physiological Entomology 20:
266-272.
Reinhard J & Kaib M (2001) Food exploitation in termites: indication for a general
feeding-stimulating signal in labial gland secretion of Isoptera. Journal of
Chemical Ecology 27: 189-201.
Reinhard J, Lacey MJ, Ibarra F, Schroeder FC, Kaib M & Lenz M (2002)
Hydroquinone: a general phagostimulating pheromone in termites. Journal of
Chemical Ecology 28: 1-14.
Remington CL (1954) The suprageneric classification of the order Thysanura
(Insecta). Annals of the Entomological Society of America 47: 277-286.
Richards OW & Davies RG (1977) Thysanura (bristle-tails; silverfish). Imms'
General Textbook of Entomology, pp. 433-443. London: Chapman & Hall.
72 Richardson CH & Seiferle EJ (1940) Barium compounds as poisons in firebrat
baits. Journal of Economic Entomology 33: 857-861.
Roelofs WL, Liu W, Hao G, Jiao H, Rooney AP & Linn Jr. CE (2002) Evolution of
moth sex pheromones via ancestral genes. Proceedings of the National
Academy of Science of the United States of America 99: 13621-13626.
Rollo CO, Czyzewska E& Borden JH (1994) Fatty acid necromones for
cockroaches. Naturwissenschaften 81: 409-410.
Romano 0 (1989) Structure and function of the male genital organs and
spermatophore formation in Thermobia domestica (Lepismatidae,
Zygentoma, Insecta). 3rd International Seminar on Apterygota, Siena, Italy,
August 21-26, 1989.
Roth LM & Cohen S (1973) Aggregation in Blattaria. Annals of the Entomological
Society of America 66: 1315-1323.
Rust MK &Appel AG (1985) Intra- and interspecific aggregation in some
nymphal blattellid cockroaches (Oictyoptera: Blattellidae). Annals of the
Entomological Society of America 78: 107-110.
Sakuma M & Fukami H (1990) The aggregation pheromone of the German
cockroach, Blattella germanica (L.) (Oictyoptera: Blattellidae): isolation and
identification of the attractant components of the pheromone. Applied
Entomology and Zoology 25: 355-368.
Sakuma M& Fukami H (1991) Aggregation pheromone of the German
cockroach, Blattella germanica (L.) (Dictyoptera Blattellidae): choice-chamber
73 assay for arrestant component(s). Applied Entomology and Zoology 26: 223
235.
Sakuma M& Fukami H (1993a) Novel steroid glycosides as aggregation
pheromone of the German cockroach. Tetrahedron Letters 34: 6059-6062.
Sakuma M & Fukami H (1993b) Aggregation arrestant pheromone of the German
cockroach, Blattella germanica L. (Dictyoptera: Blattellidae): Isolation and
structure elucidation of blattellastanoside-A and -B. Journal of Chemical
Ecology 19: 2521-2541.
Sakuma M, Fukami H& Kuwahara Y (1997a) Attractiveness of alkylamines and
aminoalcohols related to the aggregation attractant pheromone of the
German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae).
Applied Entomology and Zoology 32: 197-205.
Sakuma M, Fukami H & Kuwahara Y (1997b) Aggregation pheromone of the
German cockroach, Blaftella germanica (L.) (Dictyoptera: Blattellidae):
Controlled release of attractant amines by salt formation. Applied Entomology
and Zoology 32: 143-152.
Sauphanor B (1992) Une pheromone d'agregation chez Forficula auricularia.
Entomologia Experimentalis et Applicata 62: 285-291.
Sauphanor B& Sureau F (1993) Aggregation behaviour and interspecific
relationships in Dermaptera. Oecologia 96: 360-364.
Schaller F (1971) Indirect sperm transfer by soil arthropods. Annual Review of
Entomology 16: 407-446.
74 Scherkenbeck J, Nentwig G, Justus K, Lenz J, Gondol D, Wendler G, Dambach
M, Nischk F& Graef C (1999) Aggregation agents in German cockroach
Blattella germanica: examination of efficacy. Journal of Chemical Ecology 25:
1105-1119.
Schlamp KK, Gries R, Khaskin G, Brown K, Khaskin E, Judd GJR & Gries G (2005)
Pheromone components from body scales of female Anarsia lineafella induce
contacts by conspecific males. Journal of Chemical Ecology 31: 2897-2911.
Seiferle EJ, Adams JA, Nagel CM & Ho WC (1938) Effectiveness of fluorine
compounds as food poisons for the firebrat. Journal of Economic Entomology
31: 55-60.
Sexton OJ & Hess EH (1968) A pheromone-like dispersant affecting the local
distribution of the European house cricket, Achefa domesfica. Biological
Bulletin 134: 490-502.
Shorey HH (1973) Behavioral responses to insect pheromones. Annual Review
of Entomology 18: 349-380.
Sidebottom TH (1996) Thysanura. Fundamentals of Microanalytical Entomology:
A Practical Guide to Detecting and Identifying Filth in Foods (ed. by AR
Olsen, TH Sidebottom & SA Knight), pp. 30-31. CRC Press, London.
Slabaugh RE (1940) A new thysanuran, and a key to the domestic species of
Lepismatidae (Thysanura) found in the United States. Entomological News
51: 95-98.
Sioderbeck PE (2004) Silverfish and Firebrats. Kansas State University,
November 2004.
75 Smith EL (1970) Biology and structure of some California bristletails and
silverfish (Apterygota: Microcoryphia, Thysanura). The Pan Pacific
Entomologist 46: 212-225.
Snipes BT, Hutchins RE & Adams JA (1936) Effectiveness of sodium fluoride,
arsenic trioxide and thiodiphenylamine as food poisons for the firebrat,
Thermobia domestica (Packard). Journal of Economic Entomology 29: 421
426.
Spencer GJ (1930) The firebrat, Thermobia domestica Packard (Lepismidae) in
Canada. Canadian Entomologist 62: 1-2.
Spencer GJ (1959) Rearing of Thysanura. Culture Methods for Invertebrate
Animals (ed. by PS Galtsoff, F Lutz &JG Needham), pp. 259-261. Dover
Publishing, New York.
Stephens PA, Sutherland WJ & Freckleton RP (1999) What is the Allee effect?
Dikos 87: 185-190.
Sturm H (1956) Die Paarung beim Silberfischchen Lepisma saccharina.
Zeitschrift fOr Tierpsychologie 13: 1-12.
Sturm H (1987) Das Paarungsverhalten von Thermobia domestica (Packard)
(Lepismatidae, Zygentoma, Insecta). Braunschweig Naturkundliche Schriften
2: 693-711.
Suto C& Kumada N (1981) Secretion of dispersion-inducing substance by the
German cockroach, Blattella germanica L. (Drthoptera: Blattellidae). Applied
Entomology and Zoology 16: 113-120.
76 Swan LA & Papp CS (1972). The Common Insects of North America, p. 58.
Harper and Row Publishers, New York, NY, USA.
Sweetman HL (1938) Physical ecology of the firebrat, Thermobia domestica
(Packard). Ecological Monographs 8: 285-311.
Sweetman HL (1939) Responses of the silverfish, Lepisma saccharina L., to its
physical environment. Journal of Economic Entomology 32: 698-700.
Sweetman HL (1965) Recognition of Structural Pests and Their Damage, pp. 63,
72-74,348,352-353,358. WMC Brown Company Publishers, Dubuque, lA,
USA.
Takeda N (1980) The aggregation pheromone of some terrestrial isopod
crustaceans. Experientia 36: 1296-1297.
Tomlin AD (1979) Thysanura. Canada and its Insect Fauna, Memoirs of the
Entomological Society of Canada NO.1 08 (ed. by HV Danks), pp. 305.
Ottawa, CA.
Torto B, Njagi PGN, Hassanali A &Amiani H (1996) Aggregation pheromone
system of nymphal gregarious desert locust, Schistocerca gregaria (Forskal).
Journal of Chemical Ecology 22: 2273-2281.
Torto B, Obeng-Ofori D, Njagi PGN, Hassanali A &Amiani H (1994) Aggregation
pheromone system of adult gregarious desert locust Schistocerca gregaria
(Forskal). Journal of Chemical Ecology 20: 1749-1762.
Tregenza T & Wedell N (1997) Definitive evidence for cuticular pheromones in a
cricket. Animal Behaviour 54: 979-984.
77 Tremblay MN (2002) Microhabitat preferences and pheromone-based
aggregation behaviour of the firebrat, Thermobia domestica (Packard)
(Thysanura: Lepismatidae). MPM Thesis, Simon Fraser University, Burnaby,
BC, Canada.
Tremblay MN & Gries G (2003) Pheromone-based aggregation behaviour of the
firebrat, Thermobia domestica (Packard) (Thysanura: lepismatidae).
Chemoecology 13: 21-26.
Tremblay MN & Gries G (2006) Abiotic and biotic factors affect microhabitat
selection by the firebrat, Thermobia domestica (Packard) (Thysanura:
lepismatidae). Journal of Insect Behavior 19: 321-335.
Treves OS & Martin MM (1994) Cellulose digestion in primitive hexapods: effect
of ingested antibiotics on gut microbial populations and gut cellulase levels in
the firebrat, Thermobia domestica (Zygentoma, lepismatidae). Journal of
Chemical Ecology 20: 2003-2020.
Triplehorn CA &Johnson NF (2005) Hexapoda. Borror and Delong's
Introduction to the Study of Insects, pp. 152-168. Brooks/Cole Publishing,
Toronto, ON, CAN.
Verhoef HA (1984) Releaser and primer pheromones in Collembola. Journal of
Insect Physiology 30: 665-670.
Verhoef HA & Nagelkerke CJ (1977) Formation and ecological significance of
aggregations in Collembola. Oecologia 31: 215-226.
Verhoef HA, Nagelkerke CJ & Joosse ENG (1977) Aggregation pheromones in
Collembola. Journal of Insect Physiology 23: 1009-1013.
78 Wakeland C & Waters H (1931) Controlling the firebrat in buildings by means of
poisoned bait. Idaho Agricultural Experiment Station Bulletin 185: 1-15.
Walker KA, Jones TH & Fell RD (1993) Pheromonal basis of aggregation in
European earwig, Forficula auricularia L. (Dermaptera: Forficulidae). Journal
of Chemical Ecology 19: 2029-2038.
Wall WJ Jr. (1953) Damage to carpet materials by silverfish. Journal of Economic
Entomology 46: 1121-1122.
Wall WJ Jr. & Swift AHP (1954) The digestive enzymes of the firebrat. Journal of
Economic Entomology 47: 187-188.
Wallace RT (1942) Effect of food on the toxicity of certain stomach poisons to
Thermobia domestica (Packard). MSc Thesis, Iowa State College, Ames,
Iowa, USA.
Wendler G &Vlatten R (1993) The influence of aggregation pheromone on
walking behaviour of cockroach males (Blattella germanica L.). Journal of
Insect Physiology 39: 1041-1050.
Wertheim B, van Baalen EA, Dicke M& Vet LEM (2005) Pheromone-mediated
aggregation in nonsocial arthropods: an evolutionary ecological perspective.
Annual Review of Entomology 50: 321-346.
Wileyto EP, Boush GM & Gawin LM (1984) Function of cockroach (Orthoptera:
Blattidae) aggregation behavior. Environmental Entomology 13: 1557-1560.
Witteman AM, van den Oudenrijn S, van Leeuwen J, Akkerdaas J, van der lee
JS & Aalberse RC (1995) IgE antibodies reactive with silverfish, cockroaches
79 and chironomid are frequently found in mite-positive allergic patients.
International Archives of Allergy and Immunology 108: 165-169.
Woodbury N& Gries G (2007) Pheromone-based arrestment behavior in the
common silverfish, Lepisma saccharina, and giant silverfish, Ctenolepisma
longicaudata. Journal of Chemical Ecology 33: 1351-1358.
Wygodzinsky P (1972) A review of the silverfish (Lepismatidae, Thysanura) of
the United States and the Caribbean area. American Museum Novitates
2480: 1-26.
Wygodzinsky P (1987) Order Thysanura. Immature Insects Vol. 1 (ed. by FW
Stehr). pp. 71-74. Kendall/Hunt Publishing Company, Dubuque, Iowa, USA.
Zinkler D& Gotze M (1987) Cellulose digestion by the firebrat, Thermobia
domestica. Comparative Biochemistry and Physiology 88B: 661-666.
Zinkler D, Gotze M& Fabian K (1986) Cellulose digestion in "primitive insects"
(Apterygota) and oribatid mites. Zoologische Beitrage 30: 17-28.
Zinkler D& Polzer M (1992) Identification and characterization of digestive
proteinases from the firebrat, Thermobia domestica. Comparative
Biochemistry and Physiology 103B: 669-673.
Zungoli P (1983) Silverfish and firebrats. Pest Control 51: 56.
80