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The spotted asparagus beetle, Crioceris duodecimpunctata (L.) is an invasive host-specific pest of asparagus cultivations. To contribute to the understanding of the role of plant volatiles in host-finding by this species, behavioural and electrophysiological tests were carried out. Y-tube olfactometer bioassays, testing intact or mechanically-damaged cladophylls vs. clean air, revealed sexually-dimorphic responses with males being the only sex attracted to both plant materials. Electroantennographic (EAG) assays showed that antennae of both sexes can perceive a wide range of asparagus volatiles. Male and female EAG profiles were almost similar and (Z)-3-hexen-1-ol was by far the most EAG-active compound. (E)-2-hexenal, (±)-linalool, and 3-heptanone elicited the strongest EAG amplitude within the corresponding chemical groups. Eight of the most EAG-active compounds elicited dose-dependent responses indicating the sensitivity of male and female olfactory systems to changes in stimulus concentration. In a Y-tube olfactometer bioassay, (Z)-3-hexen-1-ol at the doses of 1, 10, and 50 μg did not elicit female attraction whereas a significant attraction at the 10 μg dose and a repellent effect at the 50 μg dose was induced in males. Sexual dimorphism of male behavioural response to host plant volatiles is discussed. This study provides a basis for future investigations that could contribute to the development of semiochemical-based monitoring and management strategies for this pest.

Previous research on Cyrba algerina (Araneae, Salticidae) has shown this jumping spider expresses predatory specialisation with respect to spiders as prey as well as inter-population variation in responsiveness to prey-spider odour. However, this earlier research pertained to a single prey species (Oecobius machadoi) and only field-collected C. algerina individuals were tested. Here we extend the previous research by using laboratory-reared, as well as field-collected, individuals of C. algerina and also by using another prey-spider species, Zelotes thorelli, as well as O. machadoi. Two localities in Portugal are considered, Sintra where C. algerina and both prey species are abundant and Tavira where C. algerina is present but neither prey species has been found. In olfactometer experiments, field-collected C. algerina individuals from Sintra, but not Tavira, were attracted to the odour of both prey species. Next, we tested the response of laboratory-reared Sintra C. algerina individuals that had been maintained with no prior experience with the odour of either prey species. We found no evidence of laboratory-reared individuals being attracted to the odour of either prey species in the olfactometer. These findings suggest that prior experience mediates responsiveness of C. algerina to the odour of local prey.

The ability to detect predators at a distance through chemical cues is often essential for prey, but spatial variation in predator presence and species may promote variability in the reactions of prey subpopulations. We collected isopods (Caecidotea communis) from three ponds: two with fish (sunfish in one, shiners in the other), and one without. We exposed individuals from these three subpopulations to kairomones and diet cues released by sunfish (Lepomis spp.) or golden shiners (Notemigonus crysoleucas). We used time-lapse photography to calculate the rate of movement and proportion of time isopods spent moving, both soon after cue introduction and twenty-five minutes later. Thus, we tested for reactions to cues, for rapid cue degradation or short-term habituation, and for effects of natal pond. The isopods from all subpopulations did not alter their rate of movement nor their percent of time moving when exposed to dechlorinated tap water or cues from sunfish. The isopods from the pond containing shiners significantly increased their proportion of time moving, and showed a not significant tendency to move more rapidly, when exposed to cues from shiners as opposed to dechlorinated tap water. Our results are the first to demonstrate that isopods may lack a behavioral response to chemicals indicating likely imminent danger from the same species of fish as occur in their natal pond.

Spiroacetals such as E-7-methyl-1,6-dioxaspiro[4,5]decane (trans-conophthorin; tC) and acetamides [predominantly N-(3-methylbutyl)acetamide; N3MBA], are two major groups of volatiles discovered in venoms of many Vespidae. In the course of testing the attractiveness of tC and N3MBA to Vespidae using Rescue® Wasp TrapStiks, a significant number of female milichiids, Desmometopa nearctica Sabrosky and D. sordida (Fallen) (Diptera: Milichiidae) were trapped as well. However, the attraction of vespid wasps was not significant at the dosages tested. We found a significant synergistic effect of tC and N3MBA in attracting Desmometopa flies. Both D. nearctica and D. sordida are kleptoparasitic species; and we conclude that females of these two milichiid flies use tC and N3MBA (and likely other volatiles) released from venom glands of the social vespids (yellowjackets, paper wasps and hornets) as kairomones to locate disturbed, injured, or freshly killed insects (vespids and/or their prey) as a protein-rich food source for egg development and production.

At early life stages invasive fishes may have no innate or learned behavioral responses to native predators. However, social cues expressed by shoal mates is one strategy species use to assess risk. By shoaling and using social cues, fishes may identify and mimic others with anti-predator behaviors to increase their own survival. Ability of non-native fishes, such as bighead carp (Hypophthalmichthys nobilis), to mimic native species that have experienced predatory threats is not known. In this experimental study, we varied the number of experienced individuals and the species composition to contrast the responses of naive juvenile bighead carp exposed to predatory kairomones when grouped with differing numbers of either experienced conspecific or experienced heterospecific (golden shiner, Notemigonus crysoleucas) shoal mates. We found fully naive groups of bighead carp did not respond to largemouth bass kairomones, but that naive individuals could mimic anti-predatory behaviors of experienced individuals, even when those experienced individuals were heterospecifics. Diverse alarm responses of bighead carp to composition and experience suggest that responses of this species are plastic. Through changing responses based on shoal experience level and composition, plastic social learning highlights how naive individuals may adapt to novel predator threats, which could inform predictions of non-native persistence in novel waterways.

In the presence of the predatory rotifer Asplanchna, some Brachionus and Keratella species develop inducible morphological, behavioral, and life history defenses that enable prey to survive predation pressure. However, whether clones belonging to the same rotifer species but with different behaviors (attached and free-swimming) exhibit divergent responses in morphology and life history remains largely unknown. In this study, neonates of an attached and a free-swimming clone of B. dorcas were exposed to media conditioned by A. brightwellii neonates at densities of 0 (control), 40, 80, and 160 ind l−1 for 24 h, and their morphological and life-table demographic parameters were measured and calculated. We showed that the Asplanchna kairomone significantly increased the propensity to attach in the attached clone only, with attached individuals effectively protected from Asplanchna predation. In response to increasing Asplanchna kairomone concentration, the attached clone did not show any morphological changes, but it did exhibit a decreased net reproductive rate and intrinsic rate of population increase. The free-swimming clone developed elongated posterolateral spines and a decreased intrinsic rate of population increase, as well as a decrease in the proportion of sexual offspring. Thus, both clones exhibited reproductive costs.

In aquatic systems, organisms largely rely on chemical cues to perceive information about the presence of predators or prey.Daphniarecognize the presence of the predatory larvae ofChaoborusvia a chemical cue, emitted by the larvae, a so-called kairomone. Upon recognition, neckteeth, an alteration of the carapace, are induced inDaphniathat reduce predation rates ofChaoborus. Neckteeth induction was often reported to entail costs. In a previous study, food quantity affected the level of neckteeth induction, with stronger neckteeth induction at low food concentrations and weak induction at high food concentrations. However, reducing neckteeth induction at high food quantities seems to be maladaptive and not in accordance with the concept that inducible defenses are associated with costs.Here, we hypothesized that weaker neckteeth induction at high food concentrations is caused by increased bacterial degradation of the kairomone. More specifically, we assume that higher algal food concentration is associated with higher bacterial abundances, which degrade the kairomone during the experiment. We tested our hypothesis by treating food algae with antibiotics before providing them as food toDaphnia. Antibiotics reduced bacterial abundances at high and low food concentrations. Reduced bacterial abundances at high food concentrations led to the same level of neckteeth induction as at low food concentrations. A linear regression revealed a significant correlation of neckteeth induction to bacterial abundances. We therefore conclude that differences in neckteeth induction at different food concentrations are not caused by the food quantity effects but by differences in bacterial degradation of the kairomone.

Daphnia pulex from a pond in Northern Italy shows four distinct defensive morphotypes, varying in the number, location and thickness of neckteeth, as the results of phenotypic plasticity. Because the frequency of the morphotypes was not related to the density of Chaoborus flavicans larvae, the main predators of D. pulex, it has been suggested that environmental factors such as long-day photoperiod, temperature or crowding might act as proximate cues for the predation risk. Here, we analysed the morphotypes of newborn D. pulex produced by mothers not exposed to chemical cues (kairomones) released by Chaoborus, but reared under environmental conditions simulating seasonal differences in predation risk. Three experimental treatments, low temperature and short-day photoperiod (16 °C 12:12 L:D), high temperature and long-day photoperiod (20 °C 14:10 L:D), and crowding under high temperature and long-day photoperiod, were compared for three clonal lineages. Almost 70% of neonates produced one or more neckteeth, but the frequencies of different morphotypes varied significantly among clones and treatments, indicating that both abiotic (temperature and photoperiod) and biotic (crowding) environmental factors affected the development of neckteeth. A characteristic S-shaped relationship between percentages of neckteethed and total juveniles per female further suggests an antipredator adaptation to high prey density. Our findings support that environmental conditions serve as proximate cues of predation risk in D. pulex contributing to the phenotypic plasticity of the neckteeth number.

Aquatic environments are constantly exposed to a cocktail of contaminants mainly due to human activities. As polluted ecosystems may simultaneously present other multiple natural stressors, the objective of the present study was to evaluate joint effect of stressors (natural and anthropogenic) on life history traits of the Neotropical cladoceran, Ceriodaphnia silvestrii. For this purpose, the effects of water conditioned with predator kairomones (fish) and environmental concentrations (sublethal) of two pesticides widely used in sugarcane monoculture in Brazil, the insecticide Regent® 800 WG (active ingredient—a.i. fipronil) and the herbicide DMA® 806 BR (a.i. 2,4-D) were evaluated using chronic toxicity testing, isolated and in mixture, for this cladoceran species. The environmental risks of pesticides for tropical freshwater biota were also estimated from the risk quotient MEC/PNEC. Among the characteristics of the life history of C. silvestrii evaluated after 8 days of exposure, compared with the mean value of control, the age of primiparous females was not affected by any evaluated treatment. However, species average survival decreased in the treatment of kairomones mixed with fipronil (FK) and in the treatment with a mixture of fipronil, 2,4-D, and kairomones (MFKD). The body length of maternal females was shorter than in the control after exposure in treatments with only kairomones (K) and FK. Fecundity of this cladoceran was reduced when exposed to FK and MFKD treatments, and the intrinsic rate of population increase significantly decreased for organisms exposed to treatment with fipronil (F) and to mixtures of fipronil and 2,4-D (MFD), MFDK, and FK. The results indicated that the combination of anthropogenic and natural stressors causes changes in C. silvestrii life history traits, which can contribute to the decline in populations, and our preliminary risk assessment results are a matter of concern regarding biota conservation.

Cuticular hydrocarbons (CHCs) are the main components of the epicuticular wax layer that in many insects functions as a barrier against desiccation. CHCs also play many other roles, including serving as sex pheromones, kairomones, primer pheromones, and colony-, caste-, species- and sex-recognition signals. In insects, CHC profiles can vary depending upon age, species, sex, and strain. Understanding factors associated with variation in hydrocarbon profiles is important for identifying potential vulnerabilities relating to pest ecology and life histories and for developing tools for pest monitoring and management strategies. In this study, we assessed potential sources of variation in CHC profiles in the navel orangeworm Amyelois transitella (Walker) (Lepidoptera: Pyralidae), an economically important pest of nut crops in California. Using coupled gas chromatography-mass spectrometry, we characterized and compared CHC profiles between adults of pyrethroid-resistant (R347) and susceptible (ALMOND) strains. We further compared CHC profiles from adults differing in age (1, 3, 5, and 7 d post-eclosion) and sex. Hydrocarbon profiles comprised 47 different CHCs in detectable quantities that ranged from C17 to C43 in chain length and included straight-chain alkanes and a variety of mono-, di-, and tri-methylalkanes. Adults from resistant populations had greater quantities of CHCs in total than those from susceptible strains, but relative quantities of individual components were similar. The six most abundant compounds were n-pentacosane, n-heptacosane, n-nonacosane, n-hentriacontane, 11,25 + 13,23 + 15,21-dimethylpentatriacontane, and 13,23 + 11,25 + 9,17-dimethylheptatriacontane. Post-eclosion, total CHCs increased with adult age, with males producing greater quantities than females at all ages. Our results show that CHC profiles vary depending on age, sex, and strain and suggest that CHC profiles may be useful as biomarkers to differentiate between insecticide- resistant and susceptible populations.

A choice test bioassay was devised to screen compounds as potential semiochemicals (e.g., kairomones or allomones that mediate aggregation, attraction or repellence) for the obligate parasitic mite, Psoroptes ovis. The choice test used filter paper discs in a 1:4 test:control ratio and was found to be a reliable, effective and efficient method. Four mammalian lipid components were assessed as potential attractants-linoleic acid, arachidonic acid, methyl myristate and squalene-, and the insect/tick repellent DEET for potential repellence. Linoleic acid was significantly attractive to P. ovis adult females and has the potential to act as an attractant. Identification of P. ovis semiochemicals, especially attractants, would be beneficial in the development of novel control methods and tools for this species. This is essential considering the increase in resistance to the limited prophylactic chemical treatments in the UK, and the high prevalence of scab infections.

Exposure of prey to predation risk usually leads to increased metabolism and decreased nutrient deposition as physiological stress responses (PSRs) of prey to their predators. Many studies using freshwater animals as models failed to find evidences as predicted from PSRs. One possible reason is that energetic costs during development of inducible defenses may lower the quantity of resources, which can be allocated to production of costly PSRs. Results obtained from the classic Brachionus-Asplanchna model indicated that inducible defenses did not alleviate PSRs in B. calyciflorus, which were manifested as increased respiration and enhanced body molar ratios of carbon (C) to nitrogen (N) and C to phosphorus (P). Moreover, activities of antioxidant systems also increased in defended B. calyciflorus. There were no alterations in somatic growth and swimming activity in B. calyciflorus when they were exposed to Asplanchna kairomones; however, we observed predator-induced –reduction of food intake in Brachionus. Our results suggest that enhanced metabolisms of defended prey in support of fight-or-flight responses are likely to be the physiological adaptation of prey to diminish hydrodynamic costs accompanied with morphological alterations (e.g., decreased swimming speed) and maintain their fitness under predation risk.

Fish kairomone-exposed Daphnia produce smaller offspring than unexposed mothers. These smaller offspring are expected to be more vulnerable to pesticides because Daphnia show size-dependent chemical sensitivity. To evaluate the potential effects of fish kairomone on the acute toxicity of an insecticide, carbaryl, in D. magna, we compared the offspring produced by adults reared in the absence and presence of fish in terms of body length and 48-h EC50. We also tested the sensitivities of juveniles of different ages but similar body sizes. The results indicated that sensitivity to carbaryl was not simply determined by the body size of D. magna. The tolerance of D. magna to pesticide may be strongly associated with individual energy storage conditions or metabolic costs generated by exposure to fish kairomone.

In aquatic ecosystems many biotic and abiotic factors influence predator–prey interactions directly or indirectly. In ephemeral pools the water level can change drastically, which may have a significant impact on predator–prey interactions, especially where ecological niches of predator(s) and prey comprise different layers of the water column. We tested the ability of benthic predatory Hoplobatrachus crassus tadpoles to detect their prey, tadpoles of the bottom-dweller Fejervarya syhadrensis and column-feeder Microhyla nilphamariensis, using visual and chemical cues, and the effect of a change in water level on the survival of the prey when exposed to H. crassus tadpoles. H. crassus tadpoles detected their prey using visual cues but not chemical ones (kairomones). Under the high-water-level condition, more M. nilphamariensis tadpoles survived than F. syhadrensis tadpoles. Under the low-water-level condition, predation levels did not differ for the two prey species. These results imply that H. crassus tadpoles hunt bottom-dwelling prey tadpoles using visual signals. M. nilphamariensis tadpoles escape the risk of predation from the bottom-dwelling predator mainly due to their ecological niche (the water column). These results showed that a change in water level can shift predation pressure between tadpoles residing in the different layers of a water column and determine the outcome of predator–prey interactions.

Collective defense is one of the most ubiquitous behaviors performed by social groups. Because of its importance, complex societies may engage a set of defensive specialists, with physical and/or neurological attributes tuned for defense against specific invaders. These strategies must be balanced, however, with the need to flexibly respond to different threat levels and sources. Insect societies rely heavily on olfaction for detecting and communicating in the context of defense. We therefore asked whether threat detection via olfaction is specialized towards invader-specific cues and how this may be integrated into defense task specialization. Colonies of the stingless bee, Tetragonisca angustula, deploy a morphologically distinct sub-caste of larger-bodied workers (soldiers) for colony defense. These soldiers transition between two different guarding tasks as they age, progressing from guarding in a hovering position near the nest entrance to guarding in a standing position on the nest entrance tube. Hovering and standing guards intercept different types of invaders: primarily heterospecific versus conspecific, respectively. We asked whether hovering and standing guarding behaviors were modulated by differential sensitivity to invader-associated olfactory stimuli; then we compared their responses to these cues to those of smaller workers that perform predominantly non-defense tasks. We exposed bees under both field and lab conditions to citral, a kairomone produced by an obligate heterospecific nest robber, primarily intercepted by hovering guards. Consistent with their roles, hovering guards were more likely to move towards citral than were either standing guards or small-bodied bees within a Y-maze. We also presented guards at field nests with dummies of conspecific versus heterospecific invader types, varying whether they included citral odors. Standing guards were more responsive to conspecific intruder scenarios than hovering guards, but heterospecific response differed by presence of citral. Standing and hovering guards responded in similar proportions when citral was absent, but the addition of citral produced a marginally non-significant reduction in standing guard participation. Our results potentially demonstrate differentiated cue-specific responses that correspond to morphological task specialization and age polyethism in these eusocial societies. Group defense is a ubiquitous function of any society, but threats are often diverse. Though defense versus non-defense task specialization has been well studied, when and how individuals sub-specialize on particular threats is less understood. We asked how age-differentiated soldier sub-types in a stingless bee differ in their innate responsiveness to olfactory cues associated with nest invader type. Consistent with behavioral roles, younger soldiers were more innately reactive to odors of an obligate heterospecific parasite, and older soldiers were more reactive to odors of conspecific intruders. This suggests that either transitions in learning or discrete cue sensitivity mediate defensive sub-specialization. This is the first study to compare behavioral responsiveness to olfactory stimuli across age-specialized soldier sub-types. Results suggest benefits of flexible allocation and prompt further studies exploring the topic of defensive sub-specialization.

We hypothesized that near-future elevated CO2 would affect the antipredatory behavior of two freshwater organisms; a pulmonate gastropod (Physella columbiana) and a cladoceran crustacean (Daphnia magna). Studies have found that pCO2 and increased acidification due to CO2 impedes fright responses to predators by activating GABAA receptors. After administration of predator-derived kairomones and conspecific alarm cues, we also briefly exposed some of the animals to gabazine which is a GABAA receptor antagonist to restore a fright response. We found that added carbon dioxide negatively affected the antipredatory behavior of both species but gabazine did not reverse this effect. To further examine the effect of CO2 and gabazine, we also tested the effect of stressful crowding, cold, and acidic conditions on the production of male daphnid offspring. An increase in ratio of male to female offspring is a common and expected response to stress by daphnids. We found that stress increased the production of males and gabazine reversed this at a pH of 5.5 but not at pH 6.2 or 6.5. Our study suggest that while the main negative effects of anthropogenic CO2 enrichment can be robust, the myriad indirect effects of CO2 make predictions about future predator prey systems less clear.

Experiments with two strains of the facultative epibiont, Brachionus rubens, tested the ability of this rotifer to avoid predation by the rotifer Asplanchna, and its propensity for sexual reproduction and consequent diapause at different population densities. Unlike some congeners, B. rubens did not have a morphological response to Asplanchna by developing longer spines or a larger body. However, it responded to this predator, and its kairomone, with a behavioral defense: a higher propensity to transition from free-swimming to attachment, typically in dense aggregations. Attached individuals were less likely to be captured and ingested, so that B. rubens outlived Asplanchna in some mixed-species cultures. Although crowding induces sex in some congeners, it did not do so in B. rubens. Instead, the proportion of sexual (mictic) daughters produced by females cultured in different volumes (0.5–60 ml) was density-independent: ~ 0.2 for the Argentina strain and ~ 0.6 for the Australia strain. Such fixed levels of sex have rarely been detected in rotifers. In B. rubens, they may be a strategy to ensure some sex with diapause at all times, but permit continued population growth via female parthenogenesis at the very high densities that normally occur on hosts and other surfaces.

Gonipterus spp. weevils (Coleoptera, Curculionidae) are pests of Eucalyptus stands in many world regions. Here, we determined the host plant volatiles that might mediate host selection behaviour in G. platensis. Eucalyptus globulus volatile organic compounds were collected by headspace solid-phase microextraction, monolithic material sorption extraction and simultaneous distillation–extraction. Gas chromatography–mass spectrometry/electroantennographic detection (GC–MS/EAD) was used to determine which compounds triggered antennal responses in the insect. Further chemical analysis of the extracted compounds was conducted using gas chromatography–mass spectrometry (GC/MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC/TOFMS). Gonipterus platensis antennal response was elicited by 51 host plant volatiles and was subsequently confirmed for 33 of these compounds using commercial standards. The behavioural response of G. platensis to individual compounds was assessed in a two-arm olfactometer with ten parallel walking chambers, coupled to video tracking and data analysis software. Weevils of known age, sex and mating status were tested. We identified eight kairomones and two allomones. The behavioural responses differed depending on insect sex and mating status. Three compounds attracted virgin females or both sexes: camphene, (+)-α-pinene and 2-phenylethanol and are potential candidates for application in integrated pest management approaches. Furthermore, the two allomones may have potential use for developing push–pull strategies.

Chemical cues from predators (kairomones) are used by many aquatic and terrestrial animals when deciding on behavioral responses to predation threats. These responses may also be affected by the animal’s physiological state (e.g., nutrition level, parasitism, or prior injury), which could alter normal responses to kairomones. In this study, we examined effects of leg autotomy (the voluntary sacrifice of a leg) on subsequent responses to predator chemical cues in females of the riparian-zone wolf spider Pardosa valens. In a fully-crossed design, spiders with all legs intact or with one leg removed were exposed to one of two cue treatments for 90 min: a control (no predator cue) or one with chemical cues (silk and excreta) from a larger sympatric wolf spider, Rabidosa santrita. We then introduced an R. santrita into each container, and recorded subsequent survival of P. valens. Survivorship was significantly higher for individuals previously exposed to predator cues than for those in the control group; however, autotomy had no effect on survivorship, which was similar for both intact and autotomized spiders in both the predator-cue and control treatments. In addition, although P. valens were more likely to be found off the substrate than on it when the predator was added in each of the four treatment pairings, this initial position did not influence survivorship. These results therefore indicate that P. valens can behaviorally respond to predator kairomones in ways that reduce their risk of predation, but that this response is unaffected by the prior sacrifice of a leg.

A comparison of juvenile predator-avoidance polymorphisms of Daphnia pulex and D. longispina in a shallow water body of Northern Italy is reported. The presence of the Chaoborus larvae resulted in juvenile adaptive predator-avoidance cyclomorphosis in both species. The frequency of induced morphotypes was higher in the small-sized D. longispina than in the large-sized D. pulex. Relative tail-spine size was higher in D. longispina than in D. pulex. D. longispina displayed much more responsiveness to Chaoborus than D. pulex. Both species showed at least 6 different defensive morphotypes that were classified according to the neckteeth number, the neckteeth position and the thickness of occipital epithelia under neckteeth. The frequencies of different morphotypes varied significantly between species. The developmental responses of Daphnia to the presence of predators are regulated at various levels, according to specific timelines of kairomone sensitive phases and developmental frame of defense trait formation. Variation of a specific timeline might be linked to flexibility in developmental responses of Daphnia to Chaoborus and seasonal variation in the frequencies of various morphotypes. Cyclomorphosis should not only be due to changes in environmental factors that directly affects risk, but also to ones that act as proxy signaling changes in predation risk.

Pest monitoring is an important tool for successful integrated pest management programmes. Blue sticky traps are important for monitoring western flower thrips, Frankliniella occidentalis, in greenhouses. However, blue sticky traps have three major weak points: (1) efficacy depends on reflection of light, which varies in intensity with fluctuating light conditions (season, diurnal rhythmic pattern), (2) they reflect broad wavelength pattern not optimally matching with maximum sensitivity of WFT photoreceptors, and (3) they offer no olfactory cues which are important for thrips orientation. This study explored the most attractive wavelength range for WFT using broad range of narrow-bandwidth light-emitting diodes (LEDs) in order to improve the attractiveness of blue sticky traps. Subsequently, trapping efficacy of the most attractive blue LED in combination with blue sticky trap and addition of an attractive lure (Lurem-TR) was evaluated in flight cages under greenhouse conditions. Release-capture studies revealed that LEDs with peak emission of 445 nm were clearly more effective than conventional blue sticky traps. In choice experiments, up to 2.7-fold and in no-choice experiment up to 2.1-fold more WFT were captured by LED-blue sticky traps compared to conventional reflecting blue sticky traps. Lurem-TR improved the performance of blue sticky traps and LED-blue sticky traps 2.3-fold and 2.0-fold, respectively, as compared to those without Lurem-TR. The addition of LEDs and kairomone lure to blue sticky traps seems promising for improving WFT trapping, specifically at low population densities especially during early infestation. However, these results should be further validated under more complex, large field conditions.

Recognising potential predators is critical for the survival and reproduction of prey animals. However, prey animals may possess an innate ability to recognise the signature odours (kairomones) of only certain native, sympatric predators, while requiring learning to recognise others. Our observations have shown that larval skipper frogs (Euphlyctis cyanophlyctis) fail to recognise kairomones of dragonfly nymph, a common predator of amphibian tadpoles with a cosmopolitan distribution. Hence, we wanted to determine if larval skipper frogs totally lack an innate mechanism to recognise kairomones of all aquatic predators, or have an innate ability to recognise kairomones of only certain predators. In a series of experiments, we tested the antipredator response of larval skipper frogs to kairomones of dragonfly nymph (Bradinopyga geminata); walking catfish (Clarias batrachus); Mozambique tilapia (Oreochromis mossambicus); two species of predatory tadpoles, Indian bullfrog (Hoplobatrachus tigerinus) and Jerdon’s bullfrog (Hoplobatrachus crassus); and the checkered keel back snake (Xenochrophis piscator). The results clearly indicate that larval skipper frogs have the innate ability to recognise kairomones of the walking catfish, both species of larval bullfrog and checkered keel back snake. However, they lack the innate ability to recognise kairomones of dragonfly nymph and Mozambique tilapia. Prey choice of the Mozambique tilapia and gape-limitation of dragonfly nymphs could be responsible for the lack of innate responses of larval skipper frogs to them. The study provides empirical evidence for the notion that prey can innately recognise certain predators.

In recent years, a significant increase in mosquito-borne diseases has been recorded worldwide. Faced with the limitations of existing methods for controlling the vector mosquito population, the development of attractants to bait traps and repellents to limit host-vector contacts could be promising and environmentally-friendly control strategies. The purpose of this study was to evaluate the effect of hydroxycoumarins and their alkyls derivatives against Aedes albopictus, the main vector of several arboviruses. Synthesis, bioassays and field trials were carried out in Madagascar. The results showed that 3, 4 and 6-hydroxycoumarins are attractive to this mosquito, 4-hydroxycoumarin being the most effective both in the laboratory and under field conditions. In addition, a good synergistic effect was found with octenol to attract mosquitoes and especially Ae. albopictus in comparison to other mosquito species living in sympatry. On the contrary, the 4-s-butoxycoumarin and 4-s-pentoxycoumarin derivatives had a repellent effect with the former showing the most significant effect. Further optimization of the dose and structure of these products will be carried out in order to maximize their utility for the control of Ae. albopictus and other mosquitoes.

In aquatic environments, chemical cues are believed to be associated with prey response to predation risk, yet few basic cue compositions are known despite the pronounced ecological and evolutionary significance of such cues. Previous work indicated that negatively-charged ions of m/z 501 are possibly a kairomone that induces anti-predator responses in amphibian tadpoles. However, work described here confirms that this specific ion species m/z 501.2886 is produced by injured tadpoles, exhibits increased spectral intensity with higher tadpole biomass, and is not produced by starved predators. These results indicate the anion is an alarm cue released from tadpoles. High resolution mass spectrometry (HR-MS) revealed a unique elemental composition for [M-H]-, m/z 501.2886, of C26H45O7S- which could not be determined in previous studies using low resolution instruments. Collision induced dissociation of m/z 501 ions formed product ions of m/z 97 and m/z 80, HSO4- and SO3-, respectively, showing the presence of sulfate. Green frog tadpoles, Lithobates clamitans, exposed to the m/z 501 anion or sodium dodecyl sulfate exhibited similar anti-predator responses, suggesting organic sulfate is a tadpole behavior modifier.

Although induced defenses are widespread in plants, the degree to which plants respond to herbivore kairomones (incidental chemicals that herbivores produce independent of herbivory), the costs and benefits of responding to cues of herbivory risk, and the ecological consequences of induced defenses remain unclear. We demonstrate that undamaged tomatoes, Solanum lycopersicum, induce defenses in response to a kairomone (locomotion mucus) of snail herbivores (Helix aspersa). Induced defense had significant costs and benefits for plants: plants exposed to snail mucus or a standard defense elicitor (methyl jasmonate, MeJA) exhibited slower growth, but also experienced less herbivory by an insect herbivore (Spodoptera exigua). We also find that kairomones from molluscan herbivores lead to deleterious effects on insect herbivores mediated through changes in plant defense, i.e., mucus-induced defenses of Solanum lycopersicum-reduced growth of S. exigua. These results suggest that incidental cues of widespread generalist herbivores might be a mechanism creating variation in plant growth, plant defense, and biotic interactions.

Mating might significantly affect the host selection behaviors of phytophagous insects. Here, we investigated the post-mating changes in behavioral and antennal responses of Pieris rapae (Lepidoptera: Pieridae) females to host plant volatiles. In two-choice bioassays using artificial plant models, mated females visited the model scented with synthetic blends (15-, 9-, or 6-components) of cabbage plant volatiles more frequently than the unscented control, whereas virgin females did not exhibit this preference. Because single compounds and the 3-component blend did not induce preferential visiting, mated females apparently utilized complex odor blends as their host-finding cue. Moreover, 2- to 4-day-old mated females visited the models, scented and unscented, more frequently than did their virgin counterparts. Therefore, mating enhanced the host-finding behavior of young females and their responsiveness to plant volatiles. Gas chromatography-electroantennographic detector analysis revealed that eight of the 15 compounds in the cabbage plant volatiles elicited responses from female antennae. However, post-mating and age-dependent changes in antennal responses were not detected. Because female peripheral (antennal) sensitivity to volatiles remained practically unchanged after emergence, post-mating changes in host selection might be attributed to changes in the central nervous system.

The invasion of the Ponto–Caspian amphipod Dikerogammarus villosus in European rivers is assumed to reduce macroinvertebrate diversity and to alter ecosystem functions. D. villosus shows an extraordinarily flexible feeding behavior including the ability to use various food sources. On the other hand, its response to predation risk seems to depend on environmental factors. To evaluate the ecological function of D. villosus, we estimated the daily food consumption for different food sources and analyzed potential effects of predator avoidance behavior on feeding. D. villosus consumption of willow leaves or chironomid larvae was quantified in 24-h laboratory experiments with and without kairomones of the European bullhead (Cottus gobio). Consumption rates were estimated based on gut content and gut evacuation rate under semi-natural laboratory conditions enabling the animals to feed over the whole time of the evacuation rate experiment. We observed very high evacuation rates and consequently high consumption rates up to 89% of body weight per day. Consumption rates differed significantly between food sources: D. villosus ingested more leaves than chironomid larvae. In contrast, predator cues did not affect the feeding of D. villosus. This might be explained by its strong refuge affinity and probably benefits its successful invasion. A comparison of the estimated consumption rates with results of an own consumption experiment (and other studies) under more artificial conditions indicated that more natural conditions result in higher consumption rates. Consequently, feeding rates from highly artificial experiments should be used with great caution to assess the ecosystem function of D. villosus.

Animals use chemical cues to find food, locate mates, and detect potential predators. Detecting cues in a risky environment can induce behavioral changes to increase survival. Rusty crayfish (Orconectes rusticus) reduce activity, increase refuge use, and make defensive displays after detecting fish predator cues. However, no studies have introduced amphibian cues. We investigated crayfish responses to hellbender salamander (Cryptobranchus alleganiensis, a dominant predator of crayfish) cues and compared these to responses to largemouth bass (Micropterus salmoides) cues. Largemouth bass occur sympatrically with hellbenders and are known to induce distinct responses in rusty crayfish. We randomly assigned crayfish to predator cue and conspecific alarm cue combinations and recorded frozen behavior, appendage movement, locomotion, and refuge use. We found crayfish increased their proportion of time spent frozen and reduced their proportion of time spent active in the tank when exposed to either predator cue. Moreover, these responses were magnified when crayfish were exposed to predator cues in combination with conspecific alarm cues. Our experiment demonstrates evidence in support of the crayfish’s ability to detect and appropriately respond to predator cues alone and in combination with conspecific alarm cues. Future work should investigate the effects of these behavioral changes on trophic dynamics in a natural system.

The response of aquatic species to contaminants is often context dependent as illustrated by the influence that predation cues can have on the toxicity of some chemicals. We sought to gain additional insight into this interaction by examining how predation cues (alarm cue and fish kairomone) influence metabolic rate and the acute toxicity of sodium chloride and cadmium to fathead minnow larvae (Pimephales promelas) and sodium chloride to Daphnia pulex neonates. Consistent with a "flight or fight" response, the metabolic rate of fish larvae was elevated in the presence of alarm cue and growth of the minnows was also significantly reduced when exposed to alarm cue. The average 48-h LC50 for fathead minnows exposed to sodium chloride was significantly lower in the presence of alarm cue and kairomone combined as compared to tests with the salt alone. Analysis of the dose and survival response indicated alarm cue increased sensitivity of the fish to mid-range salt concentrations in particular. These results suggest an energetic cost of exposure to predation cues that resulted in enhanced toxicity of NaCl. Exposure to kairomone alone had no significant effect on salt toxicity to the minnows, which could be related to a lack of previous exposure to that cue. The acute toxicity of cadmium to the fish larvae was also not affected by the presence of predation cues which could be due to a metal-induced sensory system dysfunction or reduced bioavailability of the metal due to organic exudates from the predation cues. In contrast to the fathead minnow results, the metabolic rate of D. pulex and toxicity of NaCl to the daphnids were reduced in the presence of certain predator kairomones. This suggests an anti-predator response that enhanced tolerance to the salt. This study illustrates that the effect of predation cues on toxicity of aquatic contaminants can vary significantly based on the prey species, type of cue, and chemical stressor.

The variegated coffee bug Antestiopsis thunbergii Gmelin is a key pest of Coffea arabica in East Africa. Although the bug feeds on various parts of the coffee plant, it has a strong preference for mature green berries which are essential for the bug to complete its life cycle, reproduce and enhance its longevity. To locate mature green coffee berries, we hypothesized that second instar nymphs, which are the most mobile and active feeding immature stage of the bug, must rely on key volatile compounds emitted by the host for recognition. We tested this hypothesis using behavioral and electrophysiological assays and chemical analysis. In olfactometer assays, the second instar nymphs were strongly attracted to volatiles emitted from mature green berries but avoided those from ripe coffee berries of C. arabica. Coupled gas chromatography–electroantennographic detection (GC/EAD) isolated five antenally active components from mature green berries volatiles, four of which were identified by coupled GC–mass spectrometry as toluene, anisole, methyl 3-ethyl-4-methylpentanoate and (5S,7S)-conophthorin. In concentration assays, in which second instar nymphs did not respond to toluene, they were strongly attracted to anisole, methyl 3-ethyl-4-methylpentanoate and (5S,7S)-conophthorin, and a blend from the three compounds at concentrations lower or equivalent to the natural volatile extract. Our results suggest that the blend from these three compounds allows host recognition in second instar nymphs of the variegated coffee bug and is a candidate kairomone for monitoring the pest in coffee plantations.

Parasitic wasps which attack insects infesting processed stored food need to locate their hosts hidden inside these products. Their host search is well-known to be guided by host kairomones, perceived via olfaction or contact. Among contact kairomones, host cuticular hydrocarbons (CHCs) may provide reliable information for a parasitoid. However, the chemistry of CHC profiles of hosts living in processed stored food products is largely unknown. Here we showed that the ectoparasitoid Holepyris sylvanidis uses CHCs of its host Tribolium confusum, a worldwide stored product pest, as kairomones for host location and recognition at short range. Chemical analysis of T. confusum larval extracts by gas chromatography coupled with mass spectrometry revealed a rich blend of long-chain (C25-C30) hydrocarbons, including n-alkanes, mono-, and dimethylalkanes. We further studied whether host larvae leave sufficient CHCs on a substrate where they walk along, thus allowing parasitoids to perceive a CHC trail and follow it to their host larvae. We detected 18 CHCs on a substrate that had been exposed to host larvae. These compounds were also found in crude extracts of host larvae and made up about a fifth of the CHC amount extracted. Behavioral assays showed that trails of host CHCs were followed by the parasitoids and reduced their searching time until successful host recognition. Host CHC trails deposited on different substrates were persistent for about a day. Hence, the parasitoid H. sylvanidis exploits CHCs of T. confusum larvae for host finding by following host CHC trails and for host recognition by direct contact with host larvae.

Emerald ash borer (EAB; Agrilus planipennis) is a devastating pest of ash (Fraxinus spp.) in its invaded range in North America. Its coevolved Asian hosts are more resistant and less preferred for oviposition than susceptible North American species. We compared EAB oviposition preferences and bark and canopy volatile organic compound (VOC) emissions of resistant Manchurian ash and susceptible black ash, and examined relationships between VOC profiles and oviposition. In the field, black ash was highly preferred for oviposition while no eggs were laid on Manchurian ash, and we found clear differences in the VOC profiles of Manchurian and black ash. We detected 78 compounds emitted from these species, including 16 compounds that elicited EAB antennal activity in prior studies. Four compounds were unique to black and 11 to Manchurian ash. Emission rates of 14 canopy and 19 bark volatiles varied among the two species, including four previously reported as antennally active. Specifically, 7-epi-sesquithujene (bark) emissions were greater from black ash, while β-caryophyllene (canopy), linalool (bark), and α-cubebene (bark) were emitted at higher rates by Manchurian ash. No relationships were found between the emission rate of any single compound or group of compounds (e.g. monoterpenes) suggesting that preference may be based on complex profile combinations. This is the first study to directly compare VOCs of black and Manchurian ash as well as the first to examine bark- and canopy-specific VOCs. The unique bark and canopy VOC profiles of these two species implicates potentially important variation in VOCs between a closely related resistant and susceptible species that provides a foundation for future studies of host preferences of EAB.

Culicoides biting midges (Diptera: Ceratopognidae) cause pain and distress through blood feeding, and transmit viruses that threaten both animal and human health worldwide. There are few effective tools for monitoring and control of biting midges, with semiochemical-based strategies offering the advantage of targeting host-seeking populations. In previous studies, we identified the host preference of multiple Culicoides species, including Culicoides impunctatus, as well as cattle-derived compounds that modulate the behavioral responses of C. nubeculosus under laboratory conditions. Here, we test the efficacy of these compounds, when released at different rates, in attracting C. impunctatus under field conditions in Southern Sweden. Traps releasing 1-octen-3-ol, decanal, phenol, 4-methylphenol or 3-propylphenol, when combined with carbon dioxide (CO2), captured significantly higher numbers of C. impunctatus compared to control traps baited with CO2 alone, with low release rates (0.1 mg h−1, 1 mg h−1) being generally more attractive. In contrast, traps releasing octanal or (E)-2-nonenal at 1 mg h−1 and 10 mg h−1 collected significantly lower numbers of C. impunctatus than control traps baited with CO2 only. Nonanal and 2-ethylhexanol did not affect the attraction of C. impunctatus when compared to CO2 alone at any of the release rates tested. The potential use of these semiochemicals as attractants and repellents for biting midge control is discussed.

Trissolcus japonicus is an egg parasitoid of Halyomorpha halys, brown marmorated stink bug, a severe agricultural pest in the USA. T. japonicus is being evaluated in quarantine as a classical biological control agent to manage H. halys populations in the USA. To determine T. japonicus’ potential for successful management of the pest, we performed a series of no-choice and paired-host-range tests, evaluating parasitism and host recognition in ten nontarget insects. In laboratory no-choice tests, T. japonicus successfully parasitized egg masses of seven Pentatomidae native to Oregon in addition to H. halys. Mean parasitism proportions of egg masses were greater than 40% in two species, B. dimidiata and H. abbreviatus, and were statistically similar to parasitism of H. halys. However, paired-host tests identified higher proportions of parasitized H. halys egg masses compared to four other pentatomids. T. japonicus was equally attracted to volatiles produced by H. halys and other pentatomids but demonstrated significantly longer arrestment response time on surfaces with H. halys contact kairomones. Although host acceptance patterns were similar between stink bug species, our results suggest a greater potential for parasitoid development in H. halys eggs compared to the native pentatomids. During host-range testing, we detected field populations of T. japonicus at 11 sites in Portland, OR, indicating an unintentional introduction and establishment. Further work is needed to characterize its nontarget activity and dispersal patterns in areas where H. halys causes economic damage in Oregon.

Halyomorpha halys, originating from East Asia, has become an important agricultural pest in northern temperate regions since its accidental introduction into North America in the mid-1990s and Europe in 2007. Trissolcus japonicus is the predominant egg parasitoid of this pest in its native range. Here, we tested the hypothesis that T. japonicus uses volatiles associated with H. halys adults during host location. The effects of these volatile compounds on H. halys adults were also assessed. Chemical analysis with GC-MS and electrophysiological analysis with GC-EAD revealed the presence of two bioactive volatile compounds from H. halys adults, n-tridecane and (E)-2-decenal. In the Y-tube assays, female T. japonicus were attracted by n-tridecane but strongly repelled by (E)-2-decenal. Furthermore, host searching time of female T. japonicus was significantly reduced when an H. halys egg mass was treated with n-tridecane and prolonged when treated with (E)-2-decenal or a mixture of (E)-2-decenal and n-tridecane. Male H. halys were significantly attracted by n-tridecane, whereas females had no response to this compound in the Y-tube assays. (E)-2-Decenal strongly repelled male and female H. halys in the Y-tube assays. We discuss the multifunctional kairomonal and other possible roles of these semiochemicals at different trophic levels in the context of intra- and inter-specific chemical communication, in the H. halys–T. japonicus system.

Tomato is an important vegetable crop that is cultivated for the domestic market in Kenya and other East African countries. Thrips are one of the key pests hampering the production of tomato, both by direct damage to the crop and as vectors of tospoviruses. Field experiments were carried out over two planting times to evaluate the use of sticky traps for monitoring thrips infesting tomato in East Africa. Blue, yellow, and clear sticky traps with and without a thrips lure (Lurem-TR) were tested. Field observations for thrips catches on the sticky traps were made weekly until crop senescence. Sticky traps were replaced with new ones at each observation time. Additionally, both destructive and non-destructive samplings for thrips were done at each observation. Frankliniella schultzei (Trybom) and Ceratothripoides brunneus (Bagnall) were more attracted to blue than yellow traps. Frankliniella occidentalis (Pergande) attraction to blue and yellow traps was not distinctive. The addition of Lurem-TR on traps increased captures of F. schultzei and F. occidentalis but not of C. brunneus. Blue traps with Lurem-TR captures had the highest correlation with absolute estimate of thrips density on the plants. Rainfall had significant negative correlation with thrips population on the crops. Our results show that blue traps and Lurem-TR have strong potential for improving monitoring and management of thrips on tomato.

Binary and ternary combinations of volatile organic compounds identified earlier from caterpillar-infested apple foliage caught more than one thousand individuals of both sexes of several adult tortricid leafroller species in several days of trials conducted in apple orchards in southern British Columbia. A series of combinations with phenylacetonitrile, benzyl alcohol, and/or 2-phenylethanol and acetic acid enabled substantial catches of both sexes of eye-spotted budmoth, Spilonota ocellana, oblique-banded leafroller, Choristoneura rosaceana and three-lined leafroller, Pandemis limitata. These findings suggest that new monitoring aides can be developed to seasonally track populations, enabling practical applications in surveillance of female leafroller populations for the first time. It may also be possible to develop suppression tools based on combinations of kairomone compounds originally identified from leafroller larval-damaged apple trees, given the level of attraction. The discovery of these adult tortricid attractants (aromatic compounds plus acetic acid) raises new ecological questions about evolved direct plant defences against herbivores. Larval feeding-induced attraction of adult herbivores produces signals that are potentially harmful to the plant by increasing herbivory in the same family and probably feeding guild, but evidence for effects on plant fitness is needed.

Predators have been widely demonstrated to influence developmental plasticity in aquatic prey. We investigated the body size of the amphipod Hyalella azteca raised with predatory sunfish by exposing solitary or groups of three amphipods to sunfish kairomones or a control for 30 days. Field studies indicate that small body size in H. azteca is likely an adaptive response to size-selective sunfish predation. Grouped amphipods chronically exposed to the kairomones had significantly smaller body lengths than grouped amphipods exposed to controls, while individual amphipods exhibited no significant differences. Behavioral trials revealed that grouped amphipods sought refuge less than solitary amphipods. To examine if a conspecific chemical cue was related to the reduction in body size of the grouped amphipods exposed to kairomones, individual amphipods were exposed to a combination of conspecific chemical cues and kairomones or to controls for 30 days. Amphipods exposed to kairomones in combination with conspecific cues had significantly smaller body length than amphipods exposed to conspecific cues alone. These results mirrored the group versus individual exposure experiment, suggesting that a conspecific chemical cue is required to induce an anti-predator response. The present study highlights the importance of conspecific cues for plastic responses to predators.

Prey must balance the conflicting demands of foraging and defensive behavior. Foraging under the threat of predation may be further complicated among species that engage in caudal autotomy, the loss of a portion of the tail at preformed breakage planes, because the tail may serve as an important energy storage organ and contribute to motility, culminating in a trade-off between foraging and predator avoidance. As a result of the advantages conferred by the presence of a tail, individuals that have recently undergone autotomy may be more motivated to forage despite elevated levels of threat indicated by predator kairomones. We used a full factorial design to evaluate the combined effects of body size, exposure to predator kairomones, and experience with autotomy on the latency to strike at Drosophila prey, number of strikes, and prey captured per strike by Allegheny Mountain dusky salamanders (Desmognathus ochrophaeus). In our study, caudal autotomy was the only significant main effect and influenced both the latency to attack prey and the number of strikes attempted. In terms of latency to attack prey, there was a significant interaction between body size and autotomy such that “small” salamanders (≤3.2 cm SVL) without tails delayed their foraging behavior. In terms of the number of strikes toward prey, there was a significant interaction between autotomy and exposure to predator kairomones such that individuals with intact tails exhibited a greater number of strikes, with the exception of the “large” (>3.2 cm SVL) salamanders, which performed fewer strikes when exposed to the snake kairomones. There was no significant effect on foraging efficiency, although the trend in the data suggests that autotomized individuals forage more efficiently. This study was designed to evaluate the confluence of factors related to size, caudal autotomy, and exposure to stimuli from predators and hints at the magnitude of caudal autotomy on antipredator decision-making. Our data suggest that despite the importance of tail tissue for energy storage, locomotion, and mating, salamanders without tails are cautious when foraging under elevated risk.

The aquatic immature stages of species with complex life histories exhibit a range of defense mechanisms in response to predator released kairomones (PRK). Employing these costly mechanisms often results in delayed metamorphosis. Larvae of the house mosquito Culex pipiens (Linnaeus) show a rare exception of accelerated metamorphosis in response to kairomones originated from the mosquitofish Gambusia affinis (Baird and Girard). In a series of lab experiments we examined whether this response is context-dependent with respect to food availability (i.e. applied only when food is abundant and cost is low). We examined life history variables of C. pipiens larvae, reared at different levels of food availability, either with or without PRK. We further examined the effect of PRK on the foraging behavior of the larvae at different instars. We also examined the effect of PRK-induced behavior on larvae survival under actual predation. We showed that the response of C. pipiens larvae to PRK was independent of food availability. Larvae exposed to PRK were less active and survived longer when exposed to direct predation. Exposure to both PRK and small food amounts also resulted in reduced adult size and survival period. The effects of food and PRK were independent of one another. We argue that for organisms with short development time, such as mosquitoes, decreasing time to metamorphosis may be the main feasible refuge from increased predation risk. Hence, Culex larvae exploit their capability for rapid development rate as a main anti-predator mechanism, minimizing the time spent in high-risk environments by accelerating metamorphosis, regardless of available resources, at the expense of other life history traits.

The behavioral response of the larval parasitoid Spintherus dubius (Hymenoptera: Pteromalidae) to volatile compounds derived from its Apion weevil hosts was investigated in two-choice bioassays. Odor source candidates were the larval and adult stages of weevils, clover flowers, and feces from adult weevils. Despite S. dubius being a larval parasitoid, the odor of weevil larvae isolated from the clover flowers was not attractive to female parasitoids. Surprisingly, S. dubius females were instead attracted by the odor from the feces of adult weevils. The female parasitoids were similarly attracted to the feces produced by the two main hosts, the red clover weevil (A. trifolii) and the white clover weevil (A. fulvipes). Chemical analysis of the volatile composition of feces produced by the two hosts revealed qualitatively similar odor profiles, correlating with the observed attraction by the parasitoid towards both odor sources. Some of the identified volatile compounds are commonly present in clover plant headspace fractions and may function as a kairomone to facilitate orientation by S. dubius to Apion-infested clover flowers. Larval and adult weevils were not attractive for parasitoid females, whereas, for the white clover weevil-plant association, infested flowers were highly attractive. These data show the use by the clover weevil parasitoid of an alternative source of olfactory information for locating its host.

This study identified chemicals found on the eggs of two stink bug species, one native to western North America, Euschistus conspersus, and an invasive species from Asia, Halyomorpha halys. The responses of two scelionid egg parasitoids, Trissolcus erugatus and Telenomus podisi, toward natural stink bug egg volatiles, and synthetic reconstructions of egg volatiles, were tested in bioassays. A compound, methyl (2E,4Z)-2,4-decadienoate, previously identified as the major component of the male-produced aggregation pheromone of E. conspersus, was the major volatile identified from extracts of E. conspersus eggs. In contrast, for H. halys, the sesquiterpenoids that compose the male-produced aggregation pheromone of this species were not detected on eggs, whereas the presence of hexadecanal, octadecanal, and eicosanal was detected. In laboratory olfactometer tests, both Tr. erugatus and Te. podisi females were attracted to extracts of E. conspersus eggs, and to synthetic methyl (2E,4Z)-2,4-decadienoate. However, female Tr. erugatus and Te. podisi wasps were repelled, both by extracts of H. halys eggs and by a blend of the aldehydes identified from H. halys eggs. A follow-up field study, using hexane-washed and intact E. conspersus as sentinel eggs, showed that the parasitoids Trissolcus erugatus and Gryon obesum emerged from these eggs. Sentinel hexane-washed eggs treated with 3 ng of methyl (2E,4Z)-2,4-decadienoate were parasitized more by these two species than were hexane-washed or unwashed eggs, whereas hexane-washed eggs treated with a comparable dose of the C16,18,20 aldehyde mixture were avoided by these parasitoids. In a further field experiment, Trissolcus basalis was the primary parasitoid found in sticky traps baited with methyl (2E,4Z)-2,4-decadienoate, indicating that this species was attracted to, but either did not oviposit or develop in the E. conspersus sentinel eggs in the previous experiment.

The Afro-tropical scarab Oplostomus haroldi (Witte) is a pest of honeybees in East Africa with little information available on its chemical ecology. Recently, we identified a female-produced contact sex pheromone, (Z)-9-pentacosene, from the cuticular lipids that attracted males. Here, we investigated the kairomonal basis of host location in O. haroldi. We used coupled gas chromatography/electroantennographic detection (GC/EAD) and GC/mass spectrometry to identify antennally-active compounds from volatiles collected from honeybee colonies. Antennae of both sexes of the beetle consistently detected seven components, which were identified as 3-hydroxy-2-butanone, 2,3-butanediol, butyl acetate, isopentyl acetate, butyl butyrate, hexyl acetate, and methyl benzoate. In olfactometer bioassays, both sexes responded to the full seven-component synthetic blend over solvent controls, but chose honeybee colony odors over the blend. These findings suggest that the seven compounds are components of a kairomone from honeybee colonies used by O. haroldi.

A wide range of chemical signals have been demonstrated to affect the swimming behaviour of Daphnia, including molecules associated with predation threat. In this contribution, we investigate how the concomitant presence of kairomones from the predaceous fish Lepomis macrochirus and alarm pheromones from crushed conspecifics affect the small-scale swimming behaviour of Daphnia pulicaria. In particular, we studied both the light/dark and summer/winter variations in the swimming motion of the cladoceran in the presence and absence of these infochemicals, and related them to the limnology of the environment. At summertime temperature, in the presence of light and infochemicals D. pulicaria confined its motion to the first few centimetres of the observation vessel, expressing positive phototaxis. In all other conditions, instead, no significant difference in the time spent in the upper and lower parts of the chamber was recorded. The upward displacement of D. pulicaria recorded in our experiments deviates from the most traditionally accepted downward migration used to move into darker layers to avoid visual predation. Our results highlight additional behavioural mechanisms that might be efficiently exploited by D. pulicaria to contrast predation by L. macrochirus.

The micro-crustacean Daphnia pulex is a model species for studying predator-induced defenses. When exposed to chemical cues released by its predator, the phantom midge larvae Chaoborus (Diptera), it develops protective neckteeth that reduce the predator’s success of predation in the juvenile instars. Defensive traits need to be expressed as soon as possible, which requires an early sensitivity to predator cues. We investigated the exact kairomone-sensitive period in three D. pulex strains and the timeline of neckteeth expression in early juvenile instars. We divided embryonic development into five major stages based on successive morphological landmarks. We exposed animals in these developmental stages to kairomones in order to determine the sensitive periods for neckteeth expression in the 1st and 2nd juvenile instar. Our results indicate that kairomone sensitivity starts during embryogenesis when compound eye spots begin to fuse and egg membranes are shed. Neckteeth develop with a stage-dependent time lag, being shorter when exposed in the first kairomone-sensitive stage and longer when exposed in the following developmental stages. Evolution of early kairomone sensitivity and fast defense development is a crucial step in D. pulex’s defenses against Chaoborus as it allows for protection of the most vulnerable juvenile stages.

In 2007–2012 we assessed dendrobiotic insects at three locations in stands of Pinus nigra, Pinus halepensis and Pinus sylvestris in Slovenia. The samples were collected from May to November using four (three in 2007) cross vane funnel traps per location with wet collecting cups and attractants. In 2007 we used ethanol+α-pinene, and from 2008 to 2010, ethanol+α-pinene, Pheroprax® (ipsdienol, cis-verbenol, 2-methylbut-3-en-2-ol) and Gallowit® (ipsdienol CAS 14434-41-4, ipsenol CAS 60894-96-4, DMWK CAS 115-18-4, cis-verbenol CAS 18881-04-4, α-pinene CAS 80-56-8, ethanol CAS 64-17-5) were used with traps 1.5 m above the ground. In 2011–2012 ethanol+α-pinene and Galloprotect 2D® (Galloprotect F: an aggregation pheromone [2-undecyloxy-1-ethanol] and Galloprotect A: kairomonal substances [ipsenol and 2-methyl-3-buten-1-ol]) were used with traps in the lower canopy. We collected 31,228 individuals from 45 beetle families. Curculinidae (Scolytinae, 23,325) were the most numerous, and the target family Cerambycidae was represented with 1945 specimens from 28 taxa and 25 species. In 2007 Spondylis buprestoides was by far the most abundant species. In 2008–2010 ethanol+α-pinene more effectively attracted S. buprestoides and A. rusticus, whereas Monochamus galloprovincialis showed a clear preference for Gallowit®. In 2011–2012 Galloprotect 2D® attracted significantly more cerambycids than ethanol+α-pinene, and M. galloprovincialis was by far the most numerous species. In addition to cerambycids, other saproxylic beetle species and also scolytine predators (mostly Cleridae, Histeridae, Trogossitidae) were found in the traps, highlighting the need to consider the potential negative impacts of the long-term monitoring of PWN vectors on species with important functional-trophic traits in forests.

Numerous studies have examined how predator diets influence prey responses to predation risk, but the role predator diet plays in modulating prey responses remains equivocal. We reviewed 405 predator–prey studies in 109 published articles that investigated changes in prey responses when predators consumed different prey items. In 54 % of reviewed studies, prey responses were influenced by predator diet. The value of responding based on a predator’s recent diet increased when predators specialized more strongly on particular prey species, which may create patterns in diet cue use among prey depending upon whether they are preyed upon by generalist or specialist predators. Further, prey can alleviate costs or accrue greater benefits using diet cues as secondary sources of information to fine tune responses to predators and to learn novel risk cues from exotic predators or alarm cues from sympatric prey species. However, the ability to draw broad conclusions regarding use of predator diet cues by prey was limited by a lack of research identifying molecular structures of the chemicals that mediate these interactions. Conclusions are also limited by a narrow research focus. Seventy percent of reviewed studies were performed in freshwater systems, with a limited range of model predator–prey systems, and 98 % of reviewed studies were performed in laboratory settings. Besides identifying the molecules prey use to detect predators, future studies should strive to manipulate different aspects of prey responses to predator diet across a broader range of predator–prey species, particularly in marine and terrestrial systems, and to expand studies into the field.

Mesopredators need to satisfy their energetic requirements while avoiding potentially lethal encounters with apex predators. Predators release odours into the environment through natural processes, and many antipredator adaptations are induced by the detection of these scents. We tested whether a mesopredator adjusted its behaviour when it encountered dominant predator odour in an outdoor arena. Eighteen wild-captured stoats (Mustela erminea) were exposed to the body odour of three predators: two previously encountered sympatric apex predators [cat (Felis catus) and ferret (Mustela furo)] and a novel apex predator (African wild dog (Lycaon pictus)). Foraging areas were created that varied in perceived risk, based on the presence or absence of predator odour. Detection of kairomones (chemical cues from predators) triggered cautious inspection and altered the mesopredator’s foraging activity. However, in contrast to our predictions, dominant predator odour was an attractant rather than a deterrent; food was consumed earlier in foraging areas with apex predator odour than in unscented controls. Sympatric predator odour elicited the most pronounced behavioural changes, with stoats cautiously approaching, but readily investigating, the odour source. Ferret odour stimulated the most marked changes. Mesopredators may benefit from exploitative eavesdropping as detection of predator odour primes antipredator behaviours, avoids the energetic cost of unnecessary flight and may also help a mesopredator to locate resources. This experiment highlights the role of odour in the assessment of risk and its capacity to alter foraging behaviour by a subordinate member of a predator guild. A predator encounters a myriad of scents when foraging, which can then be used to make inferences about its environment. In an outdoor arena, we tested behavioural responses of stoats to the odour of three dominant predators. Upon detecting the scent of a co-evolved predator (cat or ferret), stoats increased their cautious behaviour, but contrary to our initial prediction, they were attracted to the odour; food was consumed earlier in foraging areas with co-evolved predator odour than in unscented areas, or areas with the scent of a novel predator (African wild dog). Mesopredators ‘eavesdropped’ on the olfactory communication system of larger predators to reduce an encounter risk while obtaining food resources. Our results have practical applications for wildlife management and also increase our understanding of the role of scent communication in predator assemblages.

We propose a simple and sensitive bioassay for analyzing zooplankton escape behavior and present results of its testing on four Daphnia species under varying temperature, and in either the presence or absence of chemical cues of fish predation. In the assay, the animals are blindly transferred with a pipette through subsequent containers and their final distributions are compared. For testing the effects of a single factor, comparing distributions of the animals is a sensitive tool to detect differences in escape ability. We propose single-value measures to be used in larger experiments with multigroup comparisons in order to enable studying global effects and reduce the loss of statistical significance due to correction for multiple testing. Our results show that if escape ability is considered an important fitness component, among the tested species, which were D. longispina, D. lumholtzi, D. magna, and D. pulicaria, the last may be the most vulnerable to increased fish predation associated with increased lake water temperatures.

The European corn borer (ECB) is an important pest of maize in the northern hemisphere, but no reliable techniques exist for monitoring females during their reproductive period. In this study, we aimed to identify host-plant volatiles used by gravid Z-strain females in search for oviposition sites. Headspace of maize plants, to which gravid females orientated in a wind tunnel, was collected, and physiologically-active components were identified by using gas chromatography (GC) coupled with electroantennographic detection followed by GC-mass spectrometry. The antennae of female moths consistently responded to two maize volatiles, nonanal and decanal. Although these compounds are individually not characteristic for maize, a synthetic mix in a ratio found in maize headspace, 1:2.4 at 1 μg μl(-1) induced source contact and landing responses similar to maize plants in the wind tunnel. However, fewer females took flight in response to the mix, and those that took flight did so with an increased latency. To our knowledge, this is the first blend of host-plant volatiles that has been found to be physiologically active and to be able to induce attraction of gravid ECB females under laboratory conditions. Future tests will evaluate the attractiveness of the blend to the E-strain of ECB, the attractiveness of the blend in the field, and its potential in monitoring ECB populations.