Parasitoid Behaviour Research Articles

Selective responses of Trissolcus basalis and Telenomus podisi to chemical footprints of preferred hosts

AbstractChemical trails of the hosts (footprints) are important cues for the host searching behaviour of egg parasitoids of the family Scelionidae. The present study aims to determine the influence of the footprints of three neotropical stink bugs (Euchistus heros, Dichelops melacanthus and Nezara viridula) on the foraging behaviour of two parasitoids, Trissolcus basalis and Telenomus podisi, as well as a possible selective response to fooprints of their preferred hosts. Accordingly, Tr. basalis and Te. podisi females are allowed to forage on open arenas where E. heros, D. melacanthus or N. viridula had walked or on open arenas that had been treated with samples of an extract from each stink bug's footprints. Hexane extracts of stink bug footprints are obtained from solvent‐washed Petri dishes where insects were allowed to walk for 24 h, and these extracts were analyzed by gas chromatography‐flame ionization detection and gas chromatography‐mass spectrometry. Each parasitoid responds selectively to the footprints of their preferred host (Tr. basalis to footprints of N. viridula and Te. podisi to footprints of E. heros). Twenty‐six compounds comprising of C18 to C35 (saturated and unsaturated) and methyl branched hydrocarbons were identified in extracts of E. heros, D. melacanthus and N. viridula, respectively. There are significant differences in the total amount of the compounds identified in the footprint stink bug's extracts and also a difference in the amounts of individual compounds. In addition, the behavioural assays showed that footprints of stink bugs are stimuli that are used by egg parasitoids to search, discriminate and selectively locate their preferred host.

The effects of a parasitoid wasp of a gall-making insect on host plant characteristics and the abundance of sharing host-plant herbivore

Abstract. Triyogo A, Yasuda H. 2019. The effects of a parasitoid wasp of a gall-making insect on host plant characteristics and the abundance of sharing host-plant herbivore. Biodiversitas 20: 3499-3507. The present study has evaluated the indirect, top-down effects of a parasitoid wasp, Torymus beneficus Yasumatsu et Kamijo (Hymenoptera: Torymidae), of a gall-maker, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), on the characteristics of the chestnut tree, Castanea crenata Siebold & Zucc. (Fagales: Fagaceae), and the implications for other herbivores, the aphid, Myzocallis kuricola (Matsumura) (Homoptera: Aphididae). sharing the same host plant. In a field experiment, the behavior of D. kuriphilus larvae on chestnut tree was influenced by the T. beneficus as indicated by a small increment of gall volume. However, parasitism did not affect certain other leaf characteristics that were induced by the gall wasp. Here we show that the characteristics of chestnut tree induced by the gall-making wasp affected M. kuricola that subsequently attacked the chestnut tree. However, the hypothesis that top-down effects by natural enemies may affect other herbivores on chestnut tree through its influence on gall-making wasp was not supported in this study. This study shows that parasitism of a gall-maker does not affect the other herbivore sharing the same host plant. Furthermore, the top-down effects of the parasitoid's behavior on plants may have different effects on sharing host herbivores that attack galled plants.

Primeiro registro da vespa parasitoide Pachysomoides, associada a ninhos de Mischocyttarus cerberus e alguns comentários sobre o comportamento da espécie de vespa parasitoide

In this work, we are reporting, for the first time, a parasitoid wasp associated to the nests of Mischocyttarus cerberus, also we provide information concerning the parasitoid behavior when close to its host. We believe that the parasitism process is not easily accomplished, because the host resident females keep guarding and attacking whenever they detect any kind of parasitoid approach. Our results provide more detailed and important information about the host-parasitoid interaction behavior involving the Pachysomoides sp. and M. cerberus, which so far is scarce scientific literature.

Bottom-up regulation of a tritrophic system by Beet yellows virus infection: consequences for aphid-parasitoid foraging behaviour and development.

Effects of plants on herbivores can cascade up the food web and modulate the abundance of higher trophic levels. In agro-ecosystems, plant viruses can affect the interactions between crops, crop pests, and natural enemies. Little is known, however, about the effects of viruses on higher trophic levels, including parasitoids and their ability for pest regulation. We tested the hypothesis that a plant virus affects parasitoid foraging behaviour through cascading effects on higher trophic levels. We predicted that the semi-persistent Beet yellows virus (BYV) would influence plant (Beta vulgaris) quality, as well as aphid host (Aphis fabae) quality for a parasitoid Lysiphlebus fabarum. We determined amino acid and sugar content in healthy and infected plants (first trophic level), lipid content and body size of aphids (second trophic level) fed on both plants, as well as foraging behaviour and body size of parasitoids (third trophic level) that developed on aphids fed on both plants. Our results showed that virus infection increased sugars and decreased total amino acid content in B. vulgaris. We further observed an increase in aphid size without modification in host aphid quality (i.e., lipid content), and a slight effect on parasitoid behaviour through an increased number of antennal contacts with host aphids. Although the BYV virus clearly affected the first two trophic levels, it did not affect development or emergence of parasitoids. As the parasitoid L. fabarum does not seem to be affected by the virus, we discuss the possibility of using it for the development of targeted biological control against aphids.

The ethological significance and olfactory detection of herbivore-induced plant volatiles in interactions of plants, herbivorous insects, and parasitoids

Tritrophic interactions play a pivotal role in maintaining a functional agroecosystem. After damaged by phytophagous insects, host plants release a blend of odorants called herbivore-induced plant volatiles (HIPVs) that are attractive to natural enemies including arthropod predators and, in particular, parasitoids. In the last three decades, the identities of HIPVs have been meticulously characterized in a variety of tritrophic systems by gas chromatography–mass spectrometry (GC–MS) analysis. A plethora of HIPV components have been physiologically screened by gas chromatography-electroantennogram detection (GC-EAD) and single sensillum recording (SSR). The effects of induced odorants on behavior of herbivores and parasitoids have been investigated using Y-tube olfactometer assays and wind tunnels in the laboratory and bait trap tests in the field. Given the potential utility of parasitic wasps for pest control, the understanding of olfactory mechanisms of how HIPVs are detected by herbivores and parasitic wasps could facilitate the exploitation of parasitoids as bio-control agents. As the advent of the genome sequencing and transcriptome analysis, a large repertoire of chemosensory protein genes including odorant receptors and odorant binding proteins has been identified in herbivores and parasitic wasps, providing an unprecedented opportunity to debunk the molecular basis of olfaction-based interactions. In this review, we will summarize the recent progresses in characterization of HIPVs, the studies of olfactory mechanisms underlying tritrophic interactions with a focus on parasitoids, Lepidopteran pests, and related host plants.

Foraging behavior of two egg parasitoids exploiting chemical cues from the stink bug Piezodorus guildinii (Hemiptera: Pentatomidae).

Several parasitoids attacking the same host may lead to competition. Adult parasitoids' abilities to find, parasitize and defend hosts determine resource's retention potential. In soybean, two egg parasitoid species, Telenomus podisi and Trissolcus urichi (Hymenoptera: Platygastridae), compete on the egg masses of Piezodorus guildinii (Hemiptera: Pentatomidae) one of the major pest of this crop. We evaluated parasitoid's abilities to exploit hosts' footprints; and parasitoid's behavior when competing for the same host. Both arena residence time and retention time were similar for T. podisi and T. urichi on male or female host footprints. In its turn, T. urichi reentered the area contaminated with P. guildinii more times and staid longer in it than T. podisi. Furthermore, when competing for the same egg mass, each parasitoid species won (was in possession of the host by the end of the experiment) half of the replicates, and the number of times each wasp species contacted host in the first place was similar, without affecting replicate outcome (who ultimately won). Both species started agonistic and non-agonistic encounters. This study provides information about the potential interspecific competition between these parasitoids, which contributes to evaluate the compatibility of multiple natural enemies' biological control programs for stink bugs.

Understanding the mismatch between behaviour and development in a novel host-parasitoid association

Foraging parasitoid females should preferentially oviposit on hosts most suitable for progeny development to maximize their fitness. However, the introduction of a new host species may disrupt the link between the reliability of the cues and the expected adaptive outcome of female choice, leading to an evolutionary trap. This mismatch between behavioural acceptance and lack of development exists for North American and European egg parasitoids (Scelionidae) that encounter invasive Halyomorpha halys in areas where this exotic host has recently established. To explain this mismatch, we utilized an L9 orthogonal array design to assess and rank the influence of several critical factors characterizing host resource (host species, egg age, egg status, and surface wash) on behaviour (acceptance, patch residence and patch exploitation) and development of North American native Trissolcus euschisti egg parasitoid. Our results indicate that the host egg age is most important for behaviour, but is least influential for development of the progeny. This study suggests that the maladaptive decision to oviposit in an unsuitable host is due to a mismatch between the cues that females use, and the subsequent expected outcome of this choice. Therefore, it is the relative importance of individual factors when assessed simultaneously that influences the decision-making of female parasitoids.

Intraspecific variation in herbivore‐induced plant volatiles influences the spatial range of plant–parasitoid interactions

Chemical information influences the behaviour of many animals, thus affecting species interactions. Many animals forage for resources that are heterogeneously distributed in space and time, and have evolved foraging behaviour that utilizes information related to these resources. Herbivore‐induced plant volatiles (HIPVs), emitted by plants upon herbivore attack, provide information on herbivory to various animal species, including parasitoids. Little is known about the spatial scale at which plants attract parasitoids via HIPVs under field conditions and how intraspecific variation in HIPV emission affects this spatial scale. Here, we investigated the spatial scale of parasitoid attraction to two cabbage accessions that differ in relative preference of the parasitoid Cotesia glomerata when plants were damaged by Pieris brassicae caterpillars. Parasitoids were released in a field experiment with plants at distances of up to 60 m from the release site using intervals between plants of 10 or 20 m to assess parasitism rates over time and distance. Additionally, we observed host‐location behaviour of parasitoids in detail in a semi‐field tent experiment with plant spacing up to 8 m. Plant accession strongly affected successful host location in field set‐ups with 10 or 20 m intervals between plants. In the semi‐field set‐up, plant finding success by parasitoids decreased with increasing plant spacing, differed between plant accessions, and was higher for host‐infested plants than for uninfested plants. We demonstrate that parasitoids can be attracted to herbivore‐infested plants over large distances (10 m or 20 m) in the field, and that stronger plant attractiveness via HIPVs increases this distance (up to at least 20 m). Our study indicates that variation in plant traits can affect attraction distance, movement patterns of parasitoids, and ultimately spatial patterns of plant–insect interactions. It is therefore important to consider plant‐trait variation in HIPVs when studying animal foraging behaviour and multi‐trophic interactions in a spatial context.

Diversidad de la entomofauna asociada a vegetación aledaña a cultivos de arroz, maíz y algodón

Los sistemas de monocultivo degradan el suelo afectando sus propiedades físicas y químicas, y su regeneración es muy lenta. Con el objetivo de conocer cambios en las propiedades físicas del suelo de la Estación Experimental Tropical Pichilingue, por efecto del uso, se empleó un diseño de bloques completos al azar con tres repeticiones, en los suelos de bosque nativo y monocultivos de maíz (30 años), cacao (50 años), pasto (4 años) y palma aceitera (26 años) en diferentes profundidades cada 0,10 m hasta los 0,6 m. Se evaluaron propiedades físicas como conductividad hidráulica, densidad aparente, densidad real, porosidad total, porosidad de aireación, humedad volumétrica, textura, arcilla dispersa en agua, grado de floculación, materia orgánica e índice de materia orgánica/ limo+arcilla. Los datos fueron analizados estadísticamente y se realizó la prueba de Tuckey (P≤0,05). Se encontró que maíz, palma aceitera y pasto provocaron incrementos estadísticos significativos en la densidad aparente del suelo sin llegar a sobrepasar los niveles críticos de 1390 kg m-3 y no significativos en reducción de la porosidad total en la profundidad de 0,1-0,2 m. También, hubo alta concentración de arcillas en las primeras profundidades de los suelos cultivados, que provocó susceptibilidad a los procesos de erosión hídrica, concluyendo que el suelo bajo cultivo de palma aceitera mostró mayores diferencias estadísticas debido a la textura, afectando negativamente la densidad aparente del suelo, conductividad hidráulica, arcilla dispersa en agua, que en suma contribuyen a disminuir la estabilidad de agregados.

Learning Influences Host Versus Nonhost Discrimination and Postalighting Searching Behavior in the Tephritid Fruit Fly Parasitoid Diachasmimorpha kraussii (Hymenoptera: Braconidae).

Compared with the extensive body of research on the olfactory behavior of parasitoids of leaf-feeding insects, less is known about the fine-tuning of olfactory behavior in parasitoids that use fruit-feeding insects as hosts. We investigated whether a tephritid fruit fly parasitoid, Diachasmimorpha kraussii (Fullaway) (Hymenoptera: Braconidae), could discriminate between odors of fruits infested by larvae of a host species, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), compared to fruits infested by non-host larvae, Drosophila melanogaster (Diptera: Drosophilidae). Female wasps showed a significant preference for nectarines infested with B. tryoni, over uninfested fruits or fruits infested with D. melanogaster. When wasps were given prior experience of host or nonhost infested fruit, females demonstrated an increased ability to discriminate between host and nonhost related odors, but only when they were conditioned on host-infested (as opposed to nonhost infested) fruit. Insects provided with both host and nonhost stimuli showed no greater discriminatory learning compared to those provided with the rewarding stimuli alone. Previous experience also influenced postalighting behavior. Naïve females, and females with experience ovipositing at the top of fruit, oriented preferentially to the top of fruits upon alighting, while those with experience ovipositing at the base of fruits showed a significant difference in orientation, with 70% of wasps orientating preferentially toward the base. Similar learning-related changes were seen in search time and probing behavior. We discuss how pre- and post-alighting learning fine-tunes the behavioral responses of foraging wasps to their local environment.

Sustenance and Performance: Nutritional Reserves, Longevity, and Contest Outcomes of Fed and Starved Adult Parasitoid Wasps

Dyadic contests for possession of resources occur across a wide range of animal taxa, with contest outcome often being heavily influenced by the energetic reserves of the competitors. The majority of studied parasitoid wasps lack de novo lipogenesis, with adult lipid reserves being limited to those acquired throughout larval development. Carbohydrate- and lipid-rich adult diets can increase adult parasitoid lifespan and fecundity by potentially acting as a maintenance energy store. However, the effects of such diets on fat reserve compositions and some aspects of parasitoid behaviour contest outcome dynamics have not been examined. This study assesses the effect of a carbohydrate rich diet (honey) on the longevity, metabolic state and contest performance of Goniozus legneri, a bethylid wasp. The longevity of honey-fed diet adults was typically more than twice that of starved wasps. Compared to similarly-aged starved wasps, honey feeding increased concentrations of common haemolymph sugars and amino acids in a 3-day old and 7-day old wasps, and higher concentrations of stored lipid in7-day old wasps. However, nutritional status did not affect the outcome of dyadic contests over host possession when both contestants were either 3 days or 7 days old. While contest dynamics outcome may be unaffected by diet, it remains possible that an enhancing effect of feeding on contest ability is matched by an effect of higher value being placed on winning by starved wasps.

Potential use of Annona by products to control Drosophila suzukii and toxicity to its parasitoid Trichopria anastrephae

Extracts of Annona (Annonaceae) plants have been shown to satisfactorily control several insect pest species, especially on Neotropical regions. Here, we tested the potential use of formulated ethanolic seed-extracts of three Annona species (i.e., A. mucosa Jacq., A. muricata L. and A. sylvatica A. St.-Hil) to control the invasive pest Drosophila suzukii Matsumura, 1931 (Diptera: Drosophilidae). Using a discriminatory concentration (i.e., 2000mgL−1) for all the extracts, our results revealed that only the formulation based on A. mucosa seed-extract caused mortality above 85%, which was equivalent to the mortality caused by the synthetic insecticide spinetoram, our positive control. However, D. suzukii laid significantly fewer eggs in strawberry fruits treated with any of the formulated Annona extracts when compared to fruits that were not subjected to insecticide applications. The concentration-mortality curves for A. mucosa formulated extracts on D. suzukii were determined, and the application of this extract at LC90 (i.e., 1,995.04mgL−1) caused low mortality (33%) of the parasitoid Trichopria anastrephae Lima (Hymenoptera: Diapriidae) though ingestion exposure; however, it was toxic (70% mortality) to this natural enemy of D. suzukii by means of contact exposition. Behavior of parasitoids that survived exposure to the LC90 of A. mucosa formulated extract or of spinetoram (i.e., 105.34mgL−1) was not significantly affected. Thus, the A. mucosa formulated extract exhibited potential to be used in the management programs of D. suzukii, especially in organically based production systems where there are fewer control tools available.

Oviposition behaviour of Tamarixia radiata: effects of host density and exposure time

1. The number of hosts attacked as a function of host density is considered to be an important characteristic of parasitoid behaviour and is used to estimate key parameters such as handling time and ‘instantaneous rate of discovery’. However, little has been done to validate functional response models by direct observation of parasitoid oviposition behaviour.2. Tamarixia radiata is the most promising parasitoid for biological control attacking Diaphorina citri. Mass rearing and augmentative release seen as a potential strategy for suppression of D. citri has been documented in abandoned citrus, residential areas, and organic groves. Nevertheless, parasitism rates in culture and in the field are only moderate, leading to questions about oviposition behaviour in response to host density.3. Behaviours of gravid T. radiata females presented with susceptible host instars were categorised and documented by direct observation for 30 min and by camera recordings made over 12 h. Frequency of searching and antennating increased with host density during the 30 min. Probing rejection rates and search duration increased significantly with host density over 12 h. These factors resulted in significantly lower fecundity than expected, possibly due to host mark‐mediated deterrence within the small searching area. Females took approximately 3.6–4.2 min to probe and parasitise a host regardless of host density and exposure duration. These results were markedly different from the 52.2 min estimated from the functional response equation.4. Further experiments are required to assess the range and persistence of the putative host‐marking pheromone, and to better understand the relationship between functional response parameters and actual behaviour.

The spitting image of plant defenses: Effects of plant secondary chemistry on the efficacy of caterpillar regurgitant as an anti-predator defense.

In the arms race between plants, herbivores, and their natural enemies, specialized herbivores may use plant defenses for their own benefit, and variation in plant traits may affect the benefits that herbivores derive from these defenses. Pieris brassicae is a specialist herbivore of plants containing glucosinolates, a specific class of defensive secondary metabolites. Caterpillars of P. brassicae are known to actively spit on attacking natural enemies, including their main parasitoid, the braconid wasp Cotesia glomerata. Here, we tested the hypothesis that variation in the secondary metabolites of host plants affects the efficacy of caterpillar regurgitant as an anti‐predator defense. Using a total of 10 host plants with different glucosinolate profiles, we first studied natural regurgitation events of caterpillars on parasitoids. We then studied manual applications of water or regurgitant on parasitoids during parasitization events. Results from natural regurgitation events revealed that parasitoids spent more time grooming after attack when foraging on radish and nasturtium than on Brassica spp., and when the regurgitant came in contact with the wings rather than any other body part. Results from manual applications of regurgitant showed that all parameters of parasitoid behavior (initial attack duration, attack interruption, grooming time, and likelihood of a second attack) were more affected when regurgitant was applied rather than water. The proportion of parasitoids re‐attacking a caterpillar within 15 min was the lowest when regurgitant originated from radish‐fed caterpillars. However, we found no correlation between glucosinolate content and regurgitant effects, and parasitoid behavior was equally affected when regurgitant originated from a glucosinolate‐deficient Arabidopsis thaliana mutant line. In conclusion, host plant affects to a certain extent the efficacy of spit from P. brassicae caterpillars as a defense against parasitoids, but this is not due to glucosinolate content. The nature of the defensive compounds present in the spit remains to be determined, and the ecological relevance of this anti‐predator defense needs to be further evaluated in the field.

Response of parasitoid egg load to host dynamics and implications for egg load evolution.

A theoretical debate about whether parasitoids should be time or egg limited now recognizes both as feasible, and interest has turned to determining the circumstances under which each might arise in the field, and their implications for parasitoid behaviour and evolution. Egg loads of parasitoids sampled from the field are predicted to show a negative response to host availability, but empirical support for this relationship is scarce. We measured how a parasitoid's egg load responded to seasonal fluctuations in host population density and recorded the predicted correlation. In early summer, parasitoids were at high risk of time limitation due to low host availability, and in late summer, their offspring were at greater risk of egg limitation due to high host availability. Despite clear seasonal changes in selection pressures on egg load and lifespan, the parasitoid showed no evidence of seasonal variation in its reproductive strategy. We made minor modifications to a previously published model to explore the effects of seasonal variation in host availability on optimal investments in eggs and lifespan and obtained several new results. In particular, under circumstances analogous to some of those observed in our field study, temporal stochasticity in reproductive opportunities can cause investments in eggs to increase, rather than decrease as previously predicted. Our model results helped to explain the parasitoid's lack of a seasonally varying reproductive strategy. Understanding the evolution of parasitoid egg load would benefit from a shift of research emphasis from purely stochastic variation in parasitoid reproductive opportunities to greater consideration of host dynamics.

Infochemical use and dietary specialization in parasitoids: a meta-analysis.

Many parasitoid species use olfactory cues to locate their hosts. In tritrophic systems, parasitoids of herbivores can exploit the chemical blends emitted by plants in reaction to herbivore‐induced damage, known as herbivore‐induced plant volatiles (HIPVs). In this study, we explored the specificity and innateness of parasitoid responses to HIPVs using a meta‐analysis of data from the literature. Based on the concept of dietary specialization and infochemical use, we hypothesized that (i) specialist parasitoids (i.e., with narrow host ranges) should be attracted to specific HIPV signals, whereas generalist parasitoids (i.e., with broad host ranges) should be attracted to more generic HIPV signals and (ii) specialist parasitoids should innately respond to HIPVs, whereas generalist parasitoids should have to learn to associate HIPVs with host presence. We characterized the responses of 66 parasitoid species based on published studies of parasitoid behavior. Our meta‐analysis showed that (i) as predicted, specialist parasitoids were attracted to more specific signals than were generalist parasitoids but, (ii) contrary to expectations, response innateness depended on a parasitoid's target host life stage rather than on its degree of host specialization: parasitoids of larvae were more likely to show an innate response to HIPVs than were parasitoids of adults. This result changes our understanding of dietary specialization and highlights the need for further theoretical research that will help clarify infochemical use by parasitoids.

Foraging behaviour of an egg parasitoid exploiting plant volatiles induced by pentatomids: the role of adaxial and abaxial leaf surfaces.

Several phases of herbivorous insect attack including feeding and oviposition are known to induce plant defenses. Plants emit volatiles induced by herbivores to recruit insect parasitoids as an indirect defense strategy. So far, volatiles induced by herbivore walking and their putative role in the foraging behavior of egg parasitoids have not been investigated. In this paper we studied the response of the egg parasitoid Trissolcus basalis toward volatiles emitted by Vicia faba plants as consequence of the walking activity of the host Nezara viridula. Olfactometer bioassays were carried out to evaluate wasp responses to plants in which the abaxial or the adaxial surfaces were subjected to walking or/and oviposition. Results showed that host female walking on the abaxial but not on the adaxial surface caused a repellence effect in T. basalis 24 h after plant treatment. The emission of active volatiles also occurred when the leaf was turned upside-down, indicating a specificity of stress localization. This specificity was supported by the results, which showed that oviposition combined with feeding elicit the induction of plant volatiles, attracting the parasitoid, when the attack occurred on the abaxial surface. Analyses of plant volatile blends showed significant differences between the treatments.

An invasive insect herbivore disrupts plant volatile-mediated tritrophic signalling

Plants respond to insect attack by emission of volatile organic compounds, which recruit natural enemies of the attacking herbivore, constituting an indirect plant defence strategy. In this context, the egg parasitoid Trissolcus basalis is attracted by oviposition-induced plant volatiles emitted by Vicia faba plants as a consequence of feeding and oviposition by the pentatomid host Nezara viridula. However, this local tritrophic web could be affected by the recent invasion by the alien pentatomid bug Halyomorpha halys, an herbivore that shares the same environments as native pentatomid pests. Therefore, we investigated in laboratory conditions the possible impact of H. halys on the plant volatile-mediated signalling in the local tritrophic web V. faba–N. viridula–T. basalis. We found that T. basalis wasps were not attracted by volatiles induced in the plants by feeding and oviposition activities of H. halys, indicating specificity in the wasps’ response. However, the parasitoid attraction towards plant volatiles emitted as a consequence of feeding and oviposition by the associated host was disrupted when host, N. viridula, and non-associated host, H. halys, were concurrently present on the same plant, indicating that invasion by the alien herbivore interferes with established semiochemical webs. These outcomes are discussed in a context of multiple herbivory by evaluating the possible influences of alien insects on local parasitoid foraging behaviour.

Bactrocera oleae-induced olive VOCs routing mate searching in Psyttalia concolor males: impact of associative learning.

Olfaction is a key sense routing foraging behaviour in parasitoids. Preferences for food, mate and host stimuli can be innate in parasitic wasps. Alternatively, learning-mediated mechanisms play a crucial role. Females of the braconid parasitoid Psyttalia concolor exploit olfactory cues arising from tephritid hosts and related microhabitats. However, little is known on the olfactory stimuli routing males searching for mates. In this study, we focused on the attractiveness of Bactrocera oleae-induced olive volatiles towards P. concolor males. Furthermore, we evaluated learning occurrence in virgin males, when trained for selected unattractive volatile organic compounds (VOCs) associated with mate rewards. (E)-β-Ocimene, α-pinene and limonene attracted virgin males in Y-tube bioassays. Unattractive VOCs evoked positive chemotaxis after associative learning training. P. concolor males exposed to VOCs during a successful or unsuccessful mating, showed short-term preference for these VOCs (<1 h). However, memory consolidation was strictly dependent on reward value. Indeed, males experiencing a successful mating showed a fast consolidation into protein dependent long-term memory, appearing after 24 h. On the other hand, males experiencing a less valuable training experience (i.e. unsuccessful courtship), did not show consolidated memory after 24 h. Overall, our findings suggest that P. concolor virgin males may exploit VOCs from the host microhabitat to boost their mate searching activity, thus their reproductive success. However, since learning is a costly process, P. concolor males retained durable memories just in presence of a valuable reward, thus avoiding maladaptive behaviours.

Studi keberadaan hiperparasitoid dalam mempengaruhi perilaku imago parasitoid pada kutudaun, Aphis gossypii (Hemiptera: Aphididae)

Study Hyperparasitoid Existing Affected to Adul Parasitoid Behavior on Aphid, Aphis gossypii (Hemiptera: Aphididae). In general, hyperparasitoid is needed for establishing food and chain webs, but in contrary, it could become a limiting factor in existing biological control program. An observation to aim positive impact of hyperparasitoid existence has been carried out. Chili plant, Capsicum annuum, Aphis gossypii, Trioxys sinensis parasitoid and Aphidencyrtus sp. were used in this observation. Results showed that hyperparasitoid existence assisted parasitoid distribution. Parasitoids were placed with hyperparasitoids enhanced parasitoid distribution or dispersion two times farther compare to without hyperparasitoids. It was concluded that dispersal behaviour of hyperparasitoid adult was a parasitoid adult’s response to avoid its suppression by the hyperparasitoid and also increase parasitoid’s searching ability.