Behavior Of Moths Research Articles

Does the onset of sexual maturation terminate the expression of migratory behaviour in moths? A study of the oriental armyworm, Mythimna separata

It is generally accepted that in most insects adults are sexually immature when they initiate migration and that migratory behaviour terminates with the onset of sexual maturation. However, a few studies examining the mating status of field collected moths have suggested that sexually mature individuals may continue migrating, but in these cases it was impossible to completely eliminate the possibility that the mated females captured came from local, non-migrant populations. In this study we examined the ovarian development of Mythimna separata females captured using a vertical pointing searchlight trap on Beihuang Island in the Bohai Gulf, China, a site >40 km from land. Moths were collected from May to October from 2003 to 2008 in order to test the hypothesis that the onset of sexual maturation resulted in the termination of migratory behaviour. While females at the end of the summer had little ovarian development and were unmated, a significant proportion of those migrating northward in the early summer had developed ovaries and often had at least one spermatophore. Given that theses insects were captured while flying up to 500 m above sea level, at a site with no local populations, the findings would not support the hypothesis and suggest that both ovarian development and mating may occur during migration.

Long‐term seasonal fluctuations of lepidopteran cereal stemborers and their natural enemies on maize and wild host plants in southern Benin

Abstract The seasonal fluctuation of lepidopteran cereal stemborers on maize and wild host plants (i.e., grasses and a few sedges) was investigated in southern Benin from 1988 to 1998 by time series analysis and repeated‐measures analysis of variance (ANOVA). In addition, a walk‐in light trap was used to study the flight behavior of adult moths. On both cereals and grasses, the noctuid Sesamia calamistis was the predominant species, followed by the pyralid Eldana saccharina. The noctuid Busseola fusca was rare on both maize and wild host plants. In general, pest populations increased during the course of the year to reach peak densities during the second short rainy season, and then crashed to close to zero during the dry season. On wild host plants, egg masses and other immature stages were collected throughout the year but they were higher on wild grasses than maize during the off‐season. Thus wild host plants can be considered as refuge for both borers and natural enemies during the off‐season, when maize is not available. However, only four out of the eleven wild host species played a discernable role. S. calamistis egg densities appeared to be influenced by density‐dependent factors, suggesting an effect of natural enemies. Temperature and rainfall had a negative effect on egg abundance. Larval parasitism by a Kenyan strain of the braconid Cotesia sesamiae, which was released in southern Benin in the early 1990s, and by the tachinid Sturmiopsis parasitica varied between seasons and years but there were no discernable patterns. For both parasitoids and borer host species, parasitism was positively correlated with trap catches of adult moths. The recovery of C. sesamiae during a 2‐year period suggests that the parasitoid has established its population in southern Benin.

Testing and improving the effectiveness of trap crops for management of the diamondback moth Plutella xylostella (L.): a laboratory‐based study

The aim of this study was to assess white mustard (Sinapis alba L.) as a trap crop for diamondback moth [Plutella xylostella (L.)] on cauliflower [Brassica oleracea (L.) var. Lateman]. Moth behaviour on these plants and the importance of plant age and size in maintaining pest preference for trap crop plants were also investigated. Three times as many eggs were laid on cauliflower plants that were unprotected than on plants protected by a trap crop of white mustard. Moths remained longer on the mustard plants as a result of a doubling in the mean duration of information-providing behaviours. Plant age had little effect on P. xylostella host preference. When plant age was constant, percentage oviposition on mustard was higher when these were larger (93%) than copresented cauliflower plants, compared with when they were smaller (68%). Trap cropping with white mustard may reduce the incidence of P. xylostella in cauliflower crops. The pest management benefits of trap crops may be maximised by using trap crop plants that are larger than the main crop plants, although relatively smaller trap crop plants may still be preferred as hosts for P. xylostella per se.

Oviposition deterrent effects of Scutellaria brevibracteata Stapf. essential oil

Scutellaria is a genus of the Lamiaceae family with about 300 species widespread in temperate regions and on tropical mountains, whose essential oils possess ecological properties such as anti-feedant [1]. Scutellaria brevibracteata Stapf. is a species typical of Lebanon whose chemical composition or biological activity were never previously studied. Therefore, in this communication we report on the study of the chemical composition of the essential oil of this plant collected in June 2007 on Mont Chabrouh in Lebanon, on rocky ground at 1500m a. s.l., and on its activity against the feeding and oviposition behaviour of Spodoptera littoralis, a polyphagous insect attacking a number of plant species. The oil was isolated by hydrodistillation [2]. GC and GC/MS analyses evidenced the presence of 48 compounds; the most abundant components were sesquiterpenes (24.9%), particularly sesquiterpenes hydrocarbons (17.3%). Caryophyllene (14.4%) was recognized as the main constituent together with hexadecanoic acid (12.6%), phytol (10.7%) and 4-vinylguaiacol (10.2%). Binary choice bioassays were undertaken to investigate if the essential oil could modulate the feeding behaviour of final stadium larvae of S. littoralis; data show that S. brevibracteata essential oil did not significantly modulate larval feeding behaviour but deterred the ovoposition behaviour of adult moths.

Experimental evidence for male biased flight‐to‐light behavior in two moth species

AbstractMany studies report a greater abundance of male than female moths in light trap catches. The finding was interpreted as evidence for male‐biased attraction to light, but alternatives could not be ruled out. For example, it is not known, how much the sex ratio in the catches deviates from the natural sex ratio. To overcome these limitations, we experimentally tested the flight‐to‐light behavior of two moth species,Yponomeuta cagnagella(Hübner) (Lepidoptera: Yponomeutidae) andLigdia adustata(Denis and Schiffermüller) (Lepidoptera: Geometridae), under standardized conditions in an enclosed environment. In our test, we controlled the sex ratio, age, and population size. We recorded the moths caught in the trap and those that remained outside. Depending on the species, between 27 and 72% of all moths were caught in the light trap. We found that male moths were significantly and about 1.6 times more frequently attracted to the light than female moths. Our results were consistent for both species and hold good on the level of populations. We experimentally supported the general observation of a sexual dimorphism in the flight‐to‐light behavior of moths. Possible functional explanations include different flight activities of males and females or differences in the perception of light between males and females. Our experimental demonstration of a sexual dimorphism in the flight‐to‐light behavior of moths together with the common observation of an overrepresentation of males in light traps and other artificial light sources has implications for population and conservation biology.

Pheromone biosynthesis activating neuropeptide (PBAN): Regulatory role and mode of action

This review focuses on the endocrine regulation of reproductive behavior in moth species with particular emphasis on Helicoverpa spp. Reproductive behavior in most adult moths is dependent on the release of a unique blend of sex pheromones by the females to attract conspecific males. Mating, on the other hand, results in a loss of sexual receptivity due to the transfer of secretions from the male accessory glands, which renders females unattractive to ensuing mates. Synchronization of sexual behavior is attained by the timely release of Pheromone- Biosynthesis- Activating Neuropeptide (PBAN), a member of the PBAN/Pyrokinin neuropeptide family, characterized by a common amino acid sequence FXPRLamide motif in the C-terminus. PBAN is released into the hemolymph of females during the scotophase and is drastically reduced after mating, contributing to the loss in female receptivity. Pheromone production is age-dependent and Juvenile Hormone is involved in its regulation. PBAN activates pheromone production through its binding to a PBAN-Receptor (PBAN-R) and subsequent up-regulation of key enzymes in the biosynthetic pathway. The PBAN-R gene was identified as a member of the G-protein coupled receptor family (GPCRs), classified with the vertebrate subfamily of neuromedin U receptors. Using both biochemical and in silico mutagenesis studies, putative binding sites are predicted. Differential expression studies reveal its localization in pheromone glands, neural tissues and the male aedeagus. In the latter tissue, no activity and/or receptor-binding can be detected in response to PBAN. These results raise many questions concerning the evolutionary role of the PBAN/Pyrokinin receptors belonging to the GPCR family.

Spatial population structure of a specialist leaf‐mining moth

1. The spatial structure of natural populations may profoundly influence their dynamics. Depending on the frequency of movements among local populations and the consequent balance between local and regional population processes, earlier work has attempted to classify metapopulations into clear-cut categories, ranging from patchy populations to sets of remnant populations. In an alternative, dichotomous scheme, local populations have been classified as self-sustaining populations generating a surplus of individuals (sources) and those depending on immigration for persistence (sinks). 2. In this paper, we describe the spatial population structure of the leaf-mining moth Tischeria ekebladella, a specialist herbivore of the pedunculate oak Quercus robur. We relate moth dispersal to the distribution of oaks on Wattkast, a small island (5 km(2)) off the south-western coast of Finland. 3. We build a spatially realistic metapopulation model derived from assumptions concerning the behaviour of individual moths, and show that the model is able to explain part of the variation in observed patterns of occurrence and colonization. 4. While the species was always present on large trees, a considerable proportion of the local populations associated with small oaks showed extinction-recolonization dynamics. The vast majority of moth individuals occur on large trees. 5. According to model predictions, the dominance of local vs. regional processes in tree-specific moth dynamics varies drastically across the landscape. Most local populations may be defined broadly as 'sinks', as model simulations suggest that in the absence of immigration, only the largest oaks will sustain viable moth populations. Large trees in areas of high oak density will contribute most to the overall persistence of the metapopulation by acting as sources of moths colonizing other trees. 6. No single 'metapopulation type' will suffice to describe the oak-moth system. Instead, our study supports the notion that real populations are often a mix of earlier identified categories. The level to which local populations may persist after landscape modification will vary across the landscape, and sweeping classifications of metapopulations into single categories will contribute little to understanding how individual local populations contribute to the overall persistence of the system.

Assessment of methoxyfenozide exposure on the sexual attractiveness and responsiveness of adult codling moth, Cydia pomonella L., in small orchard blocks

The sexual attractiveness of female and the responsiveness of male codling moth, Cydia pomonella L., exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide were investigated in small orchard block experiments. The main purpose of the study was to determine whether the reported sublethal effects of methoxyfenozide affecting moth behavior also occur under field conditions. Data from the first experiment showed that in some trials untreated females were significantly more attractive to wild males than methoxyfenozide-treated females. The second experiment revealed that some released methoxyfenozide-treated males were not as responsive to calling females as untreated males, and that some untreated females were more attractive to males than methoxyfenozide-treated females. The third experiment revealed that wild males exposed to treated tree surfaces were significantly less responsive to traps than were wild males exposed to untreated trees. However, there were no significant differences in mean recaptures of released males between the untreated and treated orchard blocks. Exposure of adult C. pomonella to methoxyfenozide-treated surfaces resulted in a negative impact on male responsiveness to calling females and synthetic pheromone lures. However, the level of impact on the sexual attractiveness of treated females did not appear to be as explicit.

Influence of an endophytic fungus on host plant selection by a polyphagous moth via volatile spectrum changes

Recently the role of micro-organisms as mediators of plant-herbivore interactions has been increasingly acknowledged in ecological research. We investigated the interaction between an unspecialized root fungal endophyte (Acremonium strictum) and the polyphagous moth Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), in greenhouse and laboratory bioassays. Specifically we examined in tomato (Lycopersicon esculentum Mill.) the systemic effects of the endophytic fungus on the host selection behaviour of female moths for oviposition and the volatile profiles of host plants to understand the mechanisms acting in this multi-trophic model system. Both laboratory and field strains of H. armigera moths oviposited more on leaves of A. strictum inoculated plants as compared to endophyte-free plants, both in free flight cages and in tethered moth laboratory experiments; the moth’s preferences were significant between 10 and 18 days after inoculation. The analysis of volatile profiles showed strong quantitative differences between treatments. Endophyte inoculated plants emitted diverse terpenes and sesquiterpenes at significantly lower amounts as compared to endophyte free-plants, except for α-terpinene, which did not differ between the treatments, and trans-β-caryophyllene, which was emitted in significantly higher amounts on inoculated plants. β-Thujene and α-phellandrene accounted for 73.3 and 12.0% of total amounts of volatiles emitted from endophyte-free and inoculated plants, respectively. Our findings demonstrate that A. strictum is able to systemically influence the host selection of H. armigera moths for oviposition; conceivably mediated by the induced changes in volatile emissions (and probably additional biochemical parameters of the host plants, which have not been analysed so far). We argue for a more detailed assessment of micro-organisms invisibly colonizing plants, when studying plant-herbivore or multitrophic interactions.

Effect of learning on the oviposition preference of field-collected and laboratory-reared Chilo partellus (Lepidoptera: Crambidae) populations

Recent studies show that Vetiver grass, (Vetiveria zizanioides (L.) Nash), may have potential as a dead-end trap crop in an overall habitat management strategy for the spotted stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). Vetiver grass is highly preferred for oviposition, in spite of the fact that larval survival is extremely low on this grass. The oviposition behaviour of female Chilo partellus moths was investigated by determining the amount and size of egg batches allocated to maize and Vetiver plants and studying the effect of rearing conditions and oviposition experience on host plant selection. Two-choice preference tests were used to examine the effect of experience of maize (a suitable host plant) and Vetiver plants on the oviposition choice of C. partellus. For both field-collected and laboratory-reared moths, no significant differences were found in the preference distributions between the experienced groups. It is concluded that females do not learn, i.e. that they do not change their preference for Vetiver grass after having experienced oviposition on either maize or this grass, which supports the idea that trap cropping could have potential as a control method for C. partellus. Differences observed between field-collected and laboratory-reared moths in the amount and size of egg batches laid on maize and Vetiver grass indicate that data obtained from experiments with laboratory-reared insects should be treated with caution.

Comparative behavioral and EAG responses of female obliquebanded and redbanded leafroller moths (Lepidoptera: Tortricidae) to their sex pheromone components

Studies were conducted investigating the responses of female obliquebanded leafrollers, Choristoneura rosaceana (Harris) and redbanded leafrollers, Argyrotaenia velutinana (Walker) (Lepidoptera: Tortricidae), to components of their sex pheromone. Electroantennogram (EAG) recordings revealed significant responses from antennae of female moths of both species to the major pheromone component, (Z)-11-tetradecenyl acetate, at dosages ranging from 2 µg - 2 mg. However, tested individually, the minor pheromone components of the obliquebanded leafroller, (E)-11-tetradecenyl acetate and (Z)-11-tetradecenol, elicited little or no antennal response from conspecific females. This result was consistent for redbanded leafroller females, which showed only weak responses to the minor component (E)-11-tetradecenyl acetate at a 2 mg dosage. For both species, species-specific blend ratios of the Z and E isomers of tetradecenyl acetate did not elicit a greater antennal response than the Z isomer alone. Virgin females of each species (2-4 d old) were placed into 1-liter plastic assay chambers with constant throughput of carbon-filtered air passed through 1-liter flasks containing rubber septa loaded with (Z)- and (E)-11-tetradecenyl acetates and (Z)-11-tetradecenol for trials with female obliquebanded leafrollers or with (Z)- and (E)-11-tetradecenyl acetates and dodecyl acetate for trials with female redbanded leafrollers. Exposure to pheromone-permeated air delayed the onset of calling by 1 h and terminated the calling period 1 h earlier for both species compared with solvent-control exposed females. Furthermore, the total proportion of calling females was reduced by half in chambers receiving constant throughput of pheromone-permeated air compared with solvent controls. Exposure to pheromone-permeated air also significantly reduced egg-laying in both species compared with clean-air controls. Furthermore, application of the major pheromone component, (Z)-11-tetradecenyl acetate, at dosages ranging from 2 µg - 2 mg to wax-paper ovipositional substrates, deterred oviposition by females of both species. Our data suggest that application of synthetic sex-attractant pheromones for mating disruption of leafroller species may have deleterious effects on female moth behavior, which may contribute to pest control. Field investigations will need to be conducted to test this hypothesis.

Diel Periodicity of Emergence and Premating Reproductive Behaviors of Adult Dogwood Borer (Lepidoptera: Sesiidae)

The emergence and premating reproductive behaviors of adult dogwood borer moths, Synanthedon scitula Harris (Lepidoptera: Sesiidae), were examined under controlled conditions in the laboratory and in apple orchards in Virginia. The diel periodicity of male response to pheromone sources was recorded using traps baited with commercial pheromone lures and with a recently identified, trinary blend of dogwood borer sex pheromone components. An earlier study reporting a significant effect of pheromone trap height on the capture of male dogwood borer was revisited, using commercial lures and the new pheromone. Under a 16:8 (L:D)-h photo regimen, the emergence of male and female moths showed a diel periodicity, peaking at 0600 hours. Sexual receptivity of female moths, indicated by the onset of calling behavior, occurred in most individuals on the day after emergence and was observed only during the crepuscular period just before and after sunset. Similarly, the capture of male dogwood borer in traps deployed in July and baited with virgin female moths or pheromone lures coincided with the period of female calling behavior, peaking sharply between 2000 and 2100 hours. When pheromone-baited traps were deployed in September, the peak capture of male dogwood borer occurred earlier, between 1900 and 2000 hours. Traps baited with a commercial lure captured significantly more male dogwood borer at 1.8 m (6 ft), whereas those baited with the trinary dogwood borer sex pheromone captured similar numbers of males at elevations ranging from 1.2 to 2.4 m (4–8 ft). Use of the new dogwood borer sex pheromone has tremendously increased the precision of trapping data and has yielded reliable measurements of the behavior and abundance of male moths that pertain directly to improved monitoring and management capabilities.

Essential host plant cues in the grapevine moth

Host plant odours attract gravid insect females for oviposition. The identification of these plant volatile compounds is essential for our understanding of plant-insect relationships and contributes to plant breeding for improved resistance against insects. Chemical analysis of grape headspace and subsequent behavioural studies in the wind tunnel show that host finding in grapevine moth Lobesia botrana is encoded by a ratio-specific blend of three ubiquitous plant volatiles. The odour signal that attracts mated females to grape consists of the terpenoids (E)-beta-caryophyllene, (E)-beta-farnesene and (E)-4,8-dimethyl-1,3,7-nonatriene. These compounds represent only a fraction of the volatiles released by grapes, and they are widespread compounds known throughout the plant kingdom. Specificity may be achieved by the blend ratio, which was 100:78:9 in grape headspace. This blend elicited anemotactic behaviour in moths at remarkably small amounts. Females were attracted at release rates of only a few nanograms per minute, at levels nearly as low as those known for the attraction of male moths to the female sex pheromones.

Helicoverpa armigera (Hübner): can wheat stubble protect cotton plants against attack?

Abstract When investigating strategies for Helicoverpa armigera (Hübner) control, it is important to understand oviposition behaviour. Cotton (Gossypium hirsutum) was sown into standing wheat (Triticum astivum L.) stubble in a closed arena to investigate the effect of stubble on H. armigera moth behaviour and oviposition. Infrared cameras were used to track moths and determine whether stubble acted as a physical barrier or provided camouflage to cotton plants, thereby reducing oviposition. Searching activity was observed to peak shortly before dawn (03:00 and 04:00 h) and remained high until just after dawn (4 h window). Moths spent more time resting on cotton plants than spiralling above them, and the least time flying across the arena. While female moths spent more time searching for cotton plants growing in wheat stubble, the difference in oviposition was not significant. As similar numbers of eggs were laid on cotton plants with stubble (3.5/plant SE ±0.87) and without stubble (2.5/plant SE ±0.91), wheat stubble does not appear to provide camouflage to cotton plants. There was no significant difference in the location of eggs deposited on cotton plants with and without stubble, although more eggs were laid on the tops of cotton leaves in wheat stubble. As the spatial and temporal distribution of eggs laid on the cotton plant is a crucial component of population stability, eggs laid on the upper side of leaves on cotton plants may be more prone to fatalities caused by environmental factors such as wind and rain. Therefore, although stubble did not influence the number of eggs laid, it did affect their distribution on the plant, which may result in increased mortality of eggs on cotton plants sown into standing wheat stubble.

Effect of elevated atmospheric CO2 on oviposition behavior in Manduca sexta moths

AbstractMoths can detect changes in environmental carbon dioxide (CO2) with extremely high sensitivity, but the role of CO2 in the biology of these and other insects is not well understood. Although CO2 has been demonstrated to influence egg‐laying (oviposition) behavior of the pyralid moth Cactoblastis cactorum and nectar foraging of the sphingid moth Manduca sexta, information about the generalized role of CO2 in the behavioral biology of these species is lacking. Comparative data are necessary to properly assess how the behaviors of different species may be modified by steadily rising levels of greenhouse gases in the environment. Experiments carried out in Biosphere 2 addressed whether changes in ambient CO2 levels play a role in the oviposition behaviors of M. sexta moths. In the first series of experiments, oviposition was measured inside a flight cage with different levels of nearly ambient or elevated CO2 (400, 800 or 1200 ppm). For each concentration, hostplants used as oviposition sites were grown from seed at a CO2 level that matched the environment inside the flight cage. Under homogenous levels of CO2, we observed no significant difference in oviposition behavior at the concentrations tested. In a second series of experiments, two groups of hostplants, each surrounded by a mini free‐air CO2 enrichment (FACE) ring, were assembled inside a flight cage. In this choice test, a dynamic plume of artificially high CO2 was generated around one group of test plants, while ambient CO2 was released around the second (control) group. After eggs were counted on both plant groups, M. sexta females showed a small preference for ovipositing on the control plants. Therefore, in contrast to C. cactorum females tested under similar dynamic flow conditions, M. sexta female oviposition was not strongly inhibited by elevated CO2. To investigate this phenomenon further, we used electrophysiological recording and found that the CO2 receptor cells in M. sexta, unlike those in C. cactorum, are not readily affected by elevated levels of ambient CO2. These findings therefore suggest that elevated background levels of CO2 affect the physiology of the CO2 detection system of M. sexta to a lesser extent than that of C. cactorum, and this correlates well with the observed differences in oviposition behavior between the two species under elevated levels of environmental CO2. Hostplants of C. cactorum are crassulacean acid metabolism plants that generate nocturnal CO2 sinks on the cladode surfaces, whereas, M. sexta hostplants are nocturnal sources of respiratory CO2. We hypothesize that the abrupt and continuing increase in global ambient CO2 levels will differentially alter the behavior and physiology of moths that use CO2 sinks and sources as sensory cues to find hostplants.

Infection with the insect virus Hz-2v alters mating behavior and pheromone production in female Helicoverpa zea moths

The effect of Hz-2V virus infection on the reproductive physiology and behavior of infected Helicoverpa zea female moths was examined. In the absence of males, infected females exhibited calling behavior and called as often but for shorter periods on average than control females. As expected, control females mated with males for extend periods when they were present and did not call after mating, while virus-infected females made many frequent contacts with males and continued to call even after these contacts. Virus-infected females were found to produce five to seven times more pheromone than control females and attracted twice as many males as did control females in flight tunnel experiments. The ability of Hz-2V to alter the physiology and behavior of infected females observed here may serve to facilitate the transmission of virus in insect populations.

Body-size influence on defensive behavior of Amazonian moths: an ecophysiological approach

Ectotherm locomotion is restricted by low temperatures, and many species, such as some flying insects, need to achieve thermal thresholds before taking off. Body size influences heat exchange between an animal and the environment. Therefore, larger animals have higher thermal inertia, and necessarily spend more time in pre-flight warming up, a critical period when they remain exposed and more susceptible to predators. Thus, one could expect larger animals, along their evolutionary history, to have developed a more diversified repertoire of defensive behaviors when compared to their smaller counterparts. Moths are an interesting model for testing this hypothesis, as they exhibit considerable variation in body size and many species present pre-flight warming up by muscle shivering, an evidence of thermal restriction on locomotion. I registered the responses of 76 moths immediately after simulating the attack of a predator and then associated behavioral response to body size. I conducted the experiments at 20 and 25 degrees C to check for possible thermal restrictions on behavior, and identified animals to the family level to check for the effects of a common phylogenetic history. When disturbed at 25 degrees C, smaller moths tend to fly, while larger ones tend to run. At 20 degreedC almost all moths ran, including the smaller ones, indicating a possible thermal restriction on flight. Corroborating the proposed hypothesis, a more diversified repertoire of defensive behaviors was registered among larger moths. An alternative interpretation would be that common behaviors among related moths could be explained by common phylogenetic histories. However, two facts support the physiological restriction hypothesis: (1) the analysis within Sphingidae and Geometridae (not closely related families) showed similar results to those of the overall analysis, and (2) a more diverse repertoire of defensive behaviors was associated to the lower, and therefore more restrictive to locomotion, temperature (20 degrees C).

Infection with the insect virus Hz-2v alters mating behavior and pheromone production in female Helicoverpa zea moths

The effect of Hz-2V virus infection on the reproductive physiology and behavior of infected Helicoverpa zea female moths was examined. In the absence of males, infected females exhibited calling behavior and called as often but for shorter periods on average than control females. As expected, control females mated with males for extend periods when they were present and did not call after mating, while virus-infected females made many frequent contacts with males and continued to call even after these contacts. Virus-infected females were found to produce five to seven times more pheromone than control females and attracted twice as many males as did control females in flight tunnel experiments. The ability of Hz-2V to alter the physiology and behavior of infected females observed here may serve to facilitate the transmission of virus in insect populations.

An interaction between a specialized seed predator moth and its dioecious host plant shifting from parasitism to mutualism

Seed predator/pollinator and host plant interactions, which may be considered as antagonistic, have the potential to provide good model systems for the study of the early stages of evolution towards mutualism. I describe a relationship between a seed predator, the geometrid moth Perizoma affinitatum, and the dioecious plant Silene dioica. The moth is an obligate seed predator on its host plant. The searching and ovipositing behaviour of the female moths, number of eggs deposited per flower, the pollinating ability of the moths and the seed consumption by the larvae are described as different parameters and studied in two Finnish coastal populations. A high pollinating ability and limited seed consumption by the predator was found and discussed in relation to fitness models of P. affinitatum and S. dioica. In a mutualistic relationship there must be a balance between the costs and benefits so that the seed production by the moths is larger than the seed consumption by the larvae, given a net seed output larger than zero. The data of the parameters included in a seed production/consumption model give a positive seed output when the proportion of S. dioica flowers pollinated by other non‐predating insects is less than 60%. Accordingly, even if P. affinitatum would become the exclusive pollinator it would not endanger the survival of the host plant and both partners would benefit from this interaction. Limited seed consumption, high pollinating ability and host specificity as seen in the P. affinitatum and S. dioica interaction are considered to have been important pre‐existing qualities in the evolution of the obligate mutualisms between yucca and yucca moths and fig and fig wasps. In isolated serpentine populations where the gene flow is restricted and co‐pollinators are rare the interaction between P. affinitatum and S. dioica has the potential to shift from parasitism to mutualism.

Pheromone gland-specific fatty-acyl reductase of the silkmoth, Bombyx mori.

The C10-C18 unsaturated, acyclic, aliphatic compounds that contain an oxygenated functional group (alcohol, aldehyde, or acetate ester) are a major class of sex pheromones produced by female moths. In the biosynthesis of these pheromone components, the key enzyme required to produce the oxygenated functional groups is fatty-acyl reductase (FAR). This enzyme converts fatty-acyl pheromone precursors to their corresponding alcohols, which, depending on the moth species, can then be acetylated or oxidized to the corresponding aldehydes. Despite the significant role this enzyme has in generating the species-specific oxygenated constituents of lepidopteran sex pheromones, the enzyme has yet to be fully characterized and identified. In experiments designed to characterize a pheromone-gland-specific FAR in the silkmoth, Bombyx mori, we have isolated a cDNA clone encoding a protein homologous to a FAR from the desert shrub, Simmondsia chinensis, commonly known as jojoba. The deduced amino acid sequence of this clone predicts a 460-aa protein with a consensus NAD(P)H binding motif within the amino terminus. Northern blot analysis indicated that 2-kb transcripts of this gene were specifically expressed in the pheromone gland at 1 day before adult eclosion. Functional expression of this gene in the yeast Saccharomyces cerevisiae not only confirmed the long-chain FAR activity, but also indicated a distinct substrate specificity. Finally, the transformed yeast cells evoked typical mating behavior in male moths when cultured with the pheromone precursor fatty acid, (E,Z)-10,12-hexadecadienoic acid.