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Honeydew is a sugar-rich sweet substance excreted by the phloem-feeding herbivorous insects like aphids, leafhoppers, mealybugs and scales of the Order Hemiptera. The honeydew is generally deposite...

A chamber, named SOIL-INSECT toolbox, was developed to analyse the effect of various factors on the behaviour of soil-dwelling insects. It is equipped with sensors that continuously monitor the concentration of CO2 in the different compartments of the chamber without disturbing the air balance in the soil. The chamber can be adapted to study different stimuli, including volatile compounds, both in the presence and absence of plants. The chamber was tested using the larvae of Melolontha spp., which confi rmed its suitability for carrying out complex studies on insect-insect and insect-plant-microbiome interactions in a complex environment such as soil. The results of behavioural experiments using L3 larvae of Melolontha spp. in sterilized and natural soils revealed that the soil condition affected the behaviour of the larvae, likely due to its effect on the soil microbiome and physicochemical characteristics.

(+)-7-iso-Jasmonoyl-l-isoleucine (JA-Ile) is a lipid-derived phytohormone implicated in plant development, reproduction, and defense in response to pathogens and herbivorous insects. All these effects are instigated by the perception of JA-Ile by the COI1-JAZ co-receptor in the plant body, which in Arabidopsis thaliana is profoundly influenced by the short JAZ degron sequence (V/L)P(Q/I)AR(R/K) of the JAZ protein. Here, we report that SlJAZ-SlCOI1, the COI1-JAZ co-receptor found in the tomato plant, relies on the extended JAZ degron sequence (V/L)P(Q/I)AR(R/K)XSLX instead of the canonical JAZ degron. This finding illuminates our understanding of the mechanism of ligand perception by JA-Ile in this plant, and will inform both efforts to improve it by genetic modification of the SlCOI1-SlJAZ co-receptor, and the development of the synthetic agonists/antagonists.

Repellency of celery essential oil (Apium graveolens L.) against Spodoptera frugiperda (Lepidoptera: Noctuidae) in thelaboratory. Essential oil is one of the ingredients that has repellent ability to herbivorous insects. Celery is one of plantscontaining essential oil which may also have the repellent ability. This study was aimed to determine the differences in therepellent ability of celery essential oils compounds that were taken from 3 different locations against S. frugiperda in thelaboratory. This research was arranged in a factorial completely randomized design (CRD) with two factors. The first factorwas the origin of the celery plants (Malang, Surabaya, and Lamongan) and the second factor was the concentration level ofessential oils (1000, 2000, and 3000 ppm) which was repeated three times. The reliability test was carried out using filter papermethod. The results showed that the essential oil extracted from celery originated from Malang with 3000 ppm concentrationhad the highest percentage level of repellency (level 5) that reached 93.33% of repellency. Location and concentration factorshad no different effect on S. frugiperda larvae repellency. There was no correlation between location and concentration on therepellency of S. frugiperda larvae.

Most herbivorous insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade‐offs on alternative host plants, yet the evidence of such trade‐offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population‐genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored scale insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more‐specialized species occur on fewer of their potential hosts than do less‐specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored scale insects at two widely separated sites, more‐specialized species do not appear to outperform more generalist species., In tropical canopies, we find evidence that diet specialization in armored scale insects might be nonadaptive. Diet generalists occur on more of their potential host plants and are no less abundant than diet specialists.

Herbivorous insects have their density limited by biotic and abiotic factors, which influence their survival. For subsocial tortoise beetles (Chrysomelidae: Cassidinae) little is known about natura...

Ovipositional decisions in herbivorous insects may be affected by social information from conspecifics. Social facilitation of oviposition has been suggested for the onion fly Delia antiqua. In the current study, we found that D. antiqua oviposition was unequal between paired oviposition stations of equal quality and that more eggs were laid on an oviposition station baited with decoy flies than on the control. The increased oviposition toward the decoys continued over time >8 h. When decoys were placed upside down, the number of eggs laid did not differ between the decoy and control sides of oviposition stations, suggesting that social facilitation of oviposition is mediated by visual cues. Based on these findings, mechanisms of social facilitation of oviposition in D. antiqua were discussed.

The polyphagous cotton leafworm (Spodoptera littoralis) is one of the most destructive herbivorous insects worldwide. The present study reports the complete mitochondrial genome of S. littoralis collected from Egypt. The circular-mapping mitogenome was 15,408 bp in length with an overall A + T content of 81.1%, encoding a common set of 37 genes, including 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes. Most PCGs were found to use conventional ATN as the start codon and TAN as the stop codon. The phylogenetic tree based on the nucleic acid sequences of 13 shared PCGs of 29 Noctuidae species revealed that S. littoralis and Spodoptera litura are sister species. The data in this study will be helpful to understand geographical genetic variations, phylogenetic relationships, and species identification of S. littoralis.

Herbivorous insects, likewise, other organisms, are exposed to diverse communities of microbes from the surrounding environment. Insects and microorganisms associated with them share a range of relationships, including symbiotic and pathogenic. Insects damage plants by feeding on them and delivering plant pathogens to wounded places, from where pathogens spread over the plant. Thus insects can be considered as both pests and reservoirs or vectors of plant pathogens. Although beetles are not mentioned in the first place as plant pathogen vectors, their transmission of pathogens also takes place and affects the ecosystem. Here we present an overview of beetles as vectors of plant pathogens, including viruses, bacteria, fungi, nematodes, and Oomycota, which are responsible for developing plant diseases that can have a significant impact on crop yield and quality.

Herbivorous insects can escape the strong pressure of parasitoids by switching to feeding on new host plants. Parasitoids can adapt to this change but at the cost of changing their preferences and performance. For gregarious parasitoids, fitness changes are not always observable in the F1 generation but only in the F2 generation. Here, with the model species and gregarious parasitoid Anaphes flavipes, we examined fitness changes in the F1 generation under pressure from the simulation of host switching, and by a new two-generation approach, we determined the impact of these changes on fitness in the F2 generation. We showed that the parasitoid preference for host plants depends on hatched or oviposited learning in relation to the possibility of parasitoid decisions between different host plants. Interestingly, we showed that after simulation of parasitoids following host switching, in the new environment of a fictitious host plant, parasitoids reduced the fictitious host. At the same time, parasitoids also reduced fertility because in fictitious hosts, they are not able to complete larval development. However, from a two-generation approach, the distribution of parasitoid offspring into both native and fictitious hosts caused lower parasitoid clutch size in native hosts and higher individual offspring fertility in the F2 generation.

Crops are exposed to myriad abiotic and biotic stressors with negative consequences. Two stressors that are expected to increase under climate change are drought and infestation with herbivorous insects, including important aphid species. Expanding our understanding of the impact drought has on the plant-aphid relationship will become increasingly important under future climate scenarios. Here we use a previously characterised plant-aphid system comprising a susceptible variety of barley, a wild relative of barley with partial-aphid resistance, and the bird cherry-oat aphid to examine the drought-plant-aphid relationship. We show that drought has a negative effect on plant physiology and aphid fitness and provide evidence to suggest that plant resistance influences aphid responses to drought stress, with the expression of aphid detoxification genes increasing under drought when feeding on the susceptible plant but decreasing on the partially-resistant plant. Furthermore, we show that the expression of thionin genes, plant defensive compounds that contribute aphid resistance, increase ten-fold in susceptible plants exposed to drought stress but remain at constant levels in the partially-resistant plant, suggesting they play an important role in modulating aphid populations. This study highlights the role of plant defensive processes in mediating the interactions between the environment, plants, and herbivorous insects.

Made available in DSpace on 2022-05-01T05:29:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-01 Intensification of urbanization has been shown to be associated with taxonomic and functional modifications of biological communities, leading to changes in trophic interactions. These changes may reduce the delivery of ecosystem services provided by urban ecosystems. For instance, predation on herbivorous insects is an important ecological process operating in urban biological communities. Specifically, on one hand, herbivorous insects serve as food resources for many organisms, and on the other hand predation on herbivorous insects may reduce pest populations on urban vegetation. In this study, we assessed the relationship between urbanization intensity and bird and arthropod predation pressure on herbivorous insects across the streetscape of Xalapa (Mexico), a Neotropical city with half a million people immersed in a cloud forest context. We exposed dummy caterpillar models at 16 sites across the streetscape and two sites in a peri-urban cloud forest patch, comprising a wide range of urbanization intensities. We observed that in streets where the proportion of built cover was higher, dummy caterpillars’ attack probability was substantially lower. Moreover, we observed that caterpillars were most often attacked by arthropods (62.41%), followed by birds (21.53%), independent of built cover. Our study provides evidence that built cover surrounding streets may negatively influence the interactions between herbivorous insects and their natural enemies. Spatial Ecology and Conservation Lab (LEEC) Department of Biodiversity Institute of Biosciences Sao Paulo State University - UNESP Red de Ambiente y Sustentabilidad Instituto de Ecología A.C. Red de Biología Evolutiva Instituto de Ecología A.C. Red de Ecoetología Instituto de Ecología A.C. Spatial Ecology and Conservation Lab (LEEC) Department of Biodiversity Institute of Biosciences Sao Paulo State University - UNESP

Trichomycetes are fungi and protists living in the guts of arthropods. Herbivorous insects in freshwater habitats commonly house these microbes, and there are over 300 species described. One very common group of aquatic insects occurring in most freshwater systems is caddisflies, belonging to the Order Trichoptera. Although these are potentially good hosts for trichomycetes, there has been little published on trichomycetes in this host and none have been described from caddisflies. We collected and dissected caddisfly larvae from multiple sites in Canada from 2001 to 2018 and describe five new species of trichomycetes from trichopteran larvae. Data are presented on the prevalence and seasonal variation of trichomycetes in caddisfly larvae at one site in Nova Scotia where multi-year collections were made.

Outbreaks of eastern spruce budworm (Choristoneura fumiferana; hereafter SBW) are a major natural disturbance in coniferous forests of eastern North America. These outbreaks provide a superabundant source of food for insectivorous birds. Three species, referred to as budworm-linked warblers, exhibit strong positive numerical responses to early increases of SBW density: Tennessee Warbler (Leiothlypis peregrina), Cape May Warbler (Setophaga tigrina), and Bay-breasted Warbler (S. castanea). Their abundance increases even before defoliation is visible from aerial surveys. Budworm-linked warblers may detect new epicenters of SBW outbreaks through natal dispersal, as this movement is typically much more extensive than subsequent (breeding dispersal) movements. Our main objectives were, thus, (1) to determine whether sudden increases in the abundance of budworm-linked warblers could be used to detect early stages of SBW outbreaks, and (2) to examine age-specific responses of budworm-linked warblers to local and landscape-level habitat characteristics, in order to investigate the potential role of natal dispersal in the detection of new epicenters. To do so, we estimated the abundance of each species of budworm-linked warbler in 75 study plots sampling a gradient of SBW density and related them to 7 stand variables and landscape metrics with generalized additive mixed models. We also compared the responses of yearling (second-year; SY) and older (after-second-year; ASY) individuals to the density of SBW larvae and habitat variables at different spatial scales. We captured 31 Tennessee Warblers, 27 Cape May Warblers, and 57 Bay-breasted Warblers. The abundance of all three species of budworm-linked warblers increased with SBW larval density, but the numerical response of Bay-breasted Warbler was initiated earlier and it varied with age. SY individuals tended to be associated with stands supporting lower larval densities than ASY individuals and, as suggested by other authors, Bay-breasted Warbler appeared to be more efficient at exploiting SBW larvae at low density. For that reason, this species represents an early indicator of stands undergoing SBW outbreaks and we propose to use its abundance as an indicator to orient labour-intensive ground surveys of SBW larvae.

Under habitat loss and fragmentation, the intensity of local ecological processes involving species interactions changes pervasively, accelerating local species extinctions, and disrupting essential ecosystem functions. We addressed this issue by examining the direct population drivers of apex predators (five felid species), armadillo mesopredators, leafcutter ants (Atta sexdens and Atta cephalotes), and the indirect effects mediated by their inter‐trophic relationships in a ~25‐yr‐old land‐bridge island system formed by a hydroelectric dam in the Central Amazon. These trophic groups and pioneer tree abundance were surveyed across 34 variable‐sized islands and three continuous forest sites. Leafcutter populations were characterized in relation to their occurrence, colony density, and proportion of inactive colonies, and for each leafcutter response, we considered the direct and/or indirect effects of forest area on each trophic group. Leafcutter occupancy was best explained by the direct model, colony density by either the direct or the indirect model, and proportion of inactive colonies by an indirect model via the effects of pioneer tree abundance. The direct forest area effects were positive for apex predators and leafcutter occupancy, but negative for armadillos and pioneer trees. Yet leafcutter colony density declined in increasingly larger forest areas. The absence or low abundance of apex predators on small islands released armadillo hyper‐abundance, which contrary to expectation from top‐down control, covaried positively with leafcutter colony density. Finally, the indirect model showed that leafcutter colonies were more active under higher pioneer tree abundances. That leafcutter density increases on smaller islands whenever present is likely attributed to the hyper‐abundance of pioneer plants and canopy gaps. Although apex predators apparently suppressed armadillos, the remaining fraction of the food web seems to be controlled by bottom‐up mechanisms most likely related the overall low foliage palatability typical of wet evergreen forests. Our findings can be used to inform the long‐term viability of forest ecosystems affected by hydropower development in lowland Amazonia.

AIM: The strength of species interactions is traditionally expected to increase toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom-up (plant quality) and top-down (natural enemies) forces driving herbivory. In addition, these forces have rarely been studied together thus limiting previous attempts to understand the effect of large-scale climatic gradients on herbivory. LOCATION: Europe. TIME PERIOD: 2018–2019. MAJOR TAXA STUDIED: Quercus robur. METHODS: We simultaneously tested for latitudinal variation in plant–herbivore–natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect leaf damage and the incidence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees. RESULTS: Climatic factors rather than latitude per se were the best predictors of the large-scale (geographical) variation in the incidence of gall-inducers and leaf-miners as well as in leaf nutritional content. However, leaf damage, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by climatic factors or latitude. The incidence of leaf-miners increased with increasing concentrations of hydrolysable tannins, whereas the incidence of gall-inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C : N ratios and lignins. However, leaf traits and bird attack rates did not vary with leaf damage. MAIN CONCLUSIONS: These findings help to refine our understanding of the bottom-up and top-down mechanisms driving geographical variation in plant–herbivore interactions, and indicate the need for further examination of the drivers of herbivory on trees. This study was carried out with financial support from the French National Research Agency (ANR) in the frame of the Investments for the Future Programme, within the Cluster of Excellence COTE (Continental To coastal Ecosystems: evolution, adaptability and governance) (ANR-10-LABX-45). E.V.C. was funded by the BiodivERsA (BiodivERsA is a network of national and regional funding organisations promoting pan-European research on biodiversity and ecosystem services, and offering innovative opportunities for the conservation and sustainable management of biodiversity) project SPONFOREST (Unraveling the potential of spontaneous forest establishment for improving ecosystem functions and services in dynamic landscapes) (BiodivERsA3-2015-58). info:eu-repo/semantics/publishedVersion

Predicting how climate change affects biotic interactions and their evolution poses a challenge. Plant-insect herbivore interactions are particularly sensitive to climate change, as climate-induced changes in plant quality cascade into the performance of insect herbivores. Whereas the immediate survival of herbivore individuals depends on plastic responses to climate change induced nutritional stress, long-term population persistence via evolutionary adaptation requires genetic variation for these responses. In order to assess the prospects for population persistence under climate change, it is therefore crucial to characterise response mechanisms to climate change induced stressors, and quantify their variability in natural populations. Here, we test developmental and transcriptomic responses to water limitation induced host plant quality change in a Glanville fritillary butterfly (Melitaea cinxia) metapopulation. We combine nuclear magnetic resonance spectroscopy on the plant metabolome, larval developmental assays and an RNA seq analysis of the larval transcriptome. We observed that responses to feeding on water limited plants, in which amino acids and aromatic compounds are enriched, showed marked intrapopulation variation, with individuals of some families performing better on control and others on water limited plants. The transcriptomic responses were concordant with the developmental responses: Families exhibiting opposite developmental responses also produced opposite transcriptomic responses, e.g. in growth associated intracellular signalling. The opposite developmental and transcriptomic responses are associated with between families differences in organic compound catabolism and storage protein production. The results reveal heritable intrapopulation variability in plasticity, suggesting potential for evolutionary responses to drought-induced changes in host plant quality in the Finnish M. cinxia metapopulation.

6th International Entomophagous Insects Conference, Perugia, 9-13 September 2019. Since the late 19th century, exotic ladybirds (Coleoptera: Coccinellidae) have been used extensively for suppressing herbivorous insects of economic importance. In recent decades, the introduction of non-native biological control (BC) agents has been greatly limited due to the awareness of the potential non-target effects of introductions. Nonetheless, recent episodes of biological invasions of economically important pests have raised the need to carefully consider whether the expected benefits of pest control go beyond the possible environmental risks of introduction. To better understand the factors that contributed to successful BC programs, here we review the literature behind classical and augmentative BC using exotic ladybirds. Additionally, by means of case studies, we discuss the BC efficacy of selected exotic species, e.g., Coccinella septempunctata L., Harmonia axyridis (Pallas), and Hippodamia variegata (Goeze), and their position within the communities of predators in the introduced areas of USA, Canada, and Chile. In Europe, much of the research on exotic ladybirds has been conducted on the undesired impact of H. axyridis. Therefore, we summarize the risk assessment data for this species and review the field research investigating the ecological impact on European aphidophagous predators. According to the BIOCAT database of classical BC programs, 212 ladybird species belonging to 68 genera have been released in about 130 years of BC activity, with 14.6% of introductions having resulted in partial, substantial, or complete control of the target pest. However, because post-release evaluation of establishment and BC success has not always been conducted, this rate could underestimate the successful cases. Among other factors, ladybird establishment and pest suppression mostly depend on (1) intrinsic factors, i.e., high voracity, synchronized predator-prey life cycle, and high dispersal ability, and (2) extrinsic factors, i.e., adaptability to the new environment and landscape composition. This review contributes to improved understanding of ladybirds as exotic BC agents. info:eu-repo/semantics/publishedVersion

Grasshopper Optimization algorithm (GOA) is one of the newly introduced algorithms. The swarming ability of the grasshopper makes them unique herbivorous insects. A detailed description and step by step mathematical model of the GOA is presented in this study. GOA model for solving a real-life problem is revealed and numerical example are used to illustrate the approach. The model was implemented in MATLAB using 100 search agents (n = 100) and the maximum number of iterations was set to 1000. The best solution obtained by GOA is [101] and the best optimal value of the objective function found by GOA is 0.2361. The parameter space, the test history, the trajectory of the first grasshopper, and the convergence test are also presented in this study.

Leaf rolls by herbivorous insects evolved in various lepidopteran groups, aphids, and some attelabid weevil species. Leaf rolls are known to have a positive effect on the survival of immature insects, protecting them from natural enemies such as birds, ants, predatory wasps, and parasitoids as well as environmental stress. On the other hand, leaf rolls are considered to have a negative effect on immature survival, attracting natural enemies because of their noticeability and subsequent learning or specialization. In this study, we directly tested the effects of leaf rolls using an attelabid species by comparing the fate of immature insects between artificial leaf rolls and unrolled leaves. The results showed the following positive effects of leaf rolls: avoidance of parasitism by eulophid wasps and avoidance of egg predation by unknown predators. On the other hand, a negative effect of leaf rolls was also detected, specifically and increase in mortality via leaf roll herbivory. This study indicated that leaf shelters are not only protective refuges but are also sometimes risky hiding places, although total survival rates increased in leaf shelters.

Phasmatodea (stick and leaf insects) are herbivorous insects well camouflaged on the plant substrates due to cryptic masquerade. Also their close association with plants makes them adapted to different substrate geometries and surface topographies of the plants they imitate. During past years, stick insects gained increasing attention in attachment- and locomotion-focused research. However, most studies experimentally investigating stick insect attachment have been performed either on single attachment pads or on flat surfaces. In contrast, curved surfaces, especially twigs or stems of plants, are dominant substrates for phytophagous insects, but not much is known about the influence of curvature on their attachment. In this study, by combining the analysis of the tarsal usage with mechanical traction and pull-off force measurements, we investigate the attachment performance on curved substrates with different diameters in two species of stick insects with different tarsal length. We provide the first quantitative data for forces generated by stick insects on convex curved substrates and show that the curvature significantly influences the attachment abilities in both species. Within the studied range of substrate curvatures, traction force decreases and the pull-off force increases with increasing curvature. Shorter tarsi demonstrate reduced forces, however, the tarsus length only has an influence for diameters thinner than the tarsal length. The attachment force generally depends on the number of tarsi/tarsomeres in contact, tarsus/leg orientation and body posture on the surface. Pull-off force is also influenced by the tibiotarsal angle, with higher pull-off force for lower angles, while traction force is mainly influenced by load, i.e. adduction force.

For many organisms, dispersal may be a high-risk activity, and dispersers are likely to have behavioral, physiological, or other adaptations that increase the probability they will successfully settle in new habitat. Dispersing aphids, for example, are small-bodied, relatively weak flyers that must navigate through a complex landscape where non-host species may be much more common than suitable hosts are. While previous research has focused on how dispersing aphids locate and evaluate host species, little is known about how they interact with the non-host species they encounter while host searching. Here, I report on an experiment to test the hypothesis that dispersers of Aphis fabae spend less time evaluating non-host species with which they have had prior experience than novel non-host species. Aphids consistently spent less time in contact with familiar non-host species than novel non-host species, but the magnitude of this effect varied for different non-host species. Aphids that had previously encountered rose spent less time interacting with rose than with raspberry or goldenrod, and aphids that had previously encountered raspberry spent less time interacting with raspberry than with goldenrod. Aphids that had previously encountered goldenrod showed a less pronounced and statistically non-significant reduction in time spent interacting with goldenrod relative to either raspberry or rose. The ability to recognize previously encountered non-hosts may allow aphids to navigate more efficiently through an environment in which they face many more non-hosts than hosts, and therefore increase the probability that a disperser will ultimately locate and settle on an appropriate host plant.

Endophytic fungi have roles to protect the plant from herbivorous insects and diseases, and to support the absorption process of nutrients needed by plants for photosynthesis. Related to the important role of endophytic fungi, research was aimed to identify fungal endophytes associated with young, mature and old leaves on apple and to evaluate the effect of leaf ages on the abundance and diversity of endophytic fungi. The research was conducted in Biological Control Laboratory, Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Brawijaya from May to September 2016. Apple leaves sampling was done diagonally, and taken from nine apple trees. Based on macroscopic and microscopic characteristics, 38 isolates were identified. In the old apple leaves, it obtained 17 isolates that consisted of 5 genera, mature leaves obtained 14 isolates consisted of 6 genera, and young leaves 7 isolates obtained consists of 2 genera. The mature leaves have highest abundance and diversity of endophytic fungi compared to young and old leaves. Endophytic fungi apple leaf dominated by Aspergillus. Mature and young leaves were different from old one based on Bray-Curtis similarity.

The majority of herbivorous insects are specialized in host use. Even among insects that use many hosts, local specialization is common with a single host plant often being used in any given locality. Here, we establish such a pattern for the European swallowtail butterfly, Papilio machaon. We sampled larvae on five different natural hosts at eight sites in Sweden, each locality showing local monophagy. We ask what is the underlying reason for this pattern, (1) local genetic adaptation with each population being genetically adapted to the local host, (2) Hopkins' host selection principle with adult females retaining a memory of the larval host and preferring to oviposit on that plant, or (3) the preference/performance hypothesis which posits that females should oviposit on the local plant(s) on which larval fitness is highest. Allozyme analysis supported a relatively low level of population structuring, and oviposition preference tests showed that females from all sites had similar preference rankings of the five host plants. Hence, there was no support for local genetic adaptation or Hopkins' host selection principle. Instead, the results are consistent with the preference/performance hypothesis with local monophagy probably being implemented by a preference ranking of plants in accordance with larval performance. (Less)

As soybean (Glycine max [L.] Merrill) is an important crop throughout the world, the action of herbivorous insects responsible for economic and productivity losses is the subject of constant research. Spodoptera frugiperda (J.E. Smith) caterpillars can cause extensive damage to soybean culture; this work investigated possible harmful effects on these caterpillars associated with the possible induced defenses of soybean plants. For this purpose, we assessed the biology of the insect (leaf consumption and performance traits) and chemical composition of the soybean leaves by ultraviolet–visible spectroscopy and chemometrics of three treatments: control, mechanically wounded soybean leaves, and S. frugiperda-damaged soybean leaves. The results reveal that both types of injuries induce changes in soybean metabolism regarding the production of phenolic substances, although only the herbivore-damaged plants provoke negative effects on insect biology. Variations in carotenoid production during the circadian cycle were also found in the control group. These results confirm that the soybean plants could endure and activate chemical defense mechanisms that impair the developmental lifecycle of the insect, suggesting possibilities for sustainable control strategies.

Woody encroachment in grasslands has become increasingly problematic globally. Grazing by domestic animals can facilitate woody encroachment by reducing competition from herbaceous plants and fire frequency. Herbivorous insects and parasitic plants can each exert forces that result in the natural biological control of encroaching woody plants through reducing seeding of their host woody plants. However, the interplay of grazing and dynamics of herbivorous insects or parasitic plants, and its effects on the potential biological control of woody encroachment in grasslands remains unclear. We investigated the flower and pod damage by herbivorous insects, and the infection rates of a parasitic plant on the shrub Caragana microphylla, which is currently encroaching in Inner Mongolia Steppe, under different grazing management treatments (33-year non-grazed, 7-year non-grazed, currently grazed). Our results showed that Caragana biomass was highest at the currently grazed site, and lowest at the 33-year non-grazed site. Herbaceous plant biomass followed the opposite pattern, suggesting that grazing is indeed facilitating the encroachment of Caragana plants in Inner Mongolia Steppe. Grazing also reduced the abundance of herbivorous insects per Caragana flower, numbers of flowers and pods damaged by insect herbivores, and the infection rates of the parasitic plant on Caragana plants. Our results suggest that grazing may facilitate woody encroachment in grasslands not only through canonical mechanisms (e.g. competitive release via feeding on grasses, reductions in fires, etc.), but also by limiting natural biological controls of woody plants (herbivorous insects and parasitic plants). Thus, management efforts must focus on preventing overgrazing to better protect grassland ecosystems from woody encroachment., Summary: Grazing can negatively affect herbivorous insects and parasitic plants on woody plants, and thus limit the effectiveness of their natural biological control effects on woody encroachment.

Social plasticity may be an important originator of divergence in mating signals and other sexual traits. Understanding the evolutionary causes and consequences of social plasticity requires analyzing how different features of the social environment influence the expression of signals and preferences. Here we focus on experience of signaling environments. We adopt the vantage point of a hypothetical focal juvenile individual, and ask whether its experience of the interactions between other individuals in the group would vary across groups of different size and species composition. We worked with Enchenopa treehoppers, group-living herbivorous insects that communicate with plant-borne vibrational signals as juveniles and adults. We manipulated group composition and size experimentally and monitored the behavior of the juvenile treehoppers. We found that the treehoppers’ signaling rates varied with group type, size, and disturbance. Although our results likely underestimate the range of variation in behavio...

Brazilian peppertree, Schinus terebinthifolia Raddi (Anacardiaceae), is a South American plant that is highly invasive in Florida. The impact of insect herbivores on the performance of Brazilian peppertree was evaluated at two locations in Florida using an insecticide exclusion method. Although 38 species of insect herbivores were collected on the invasive tree, there were no differences in growth or reproductive output of insecticide protected and unprotected trees, providing evidence that insect feeding had no measurable impact on tree performance. The majority of insects collected on Brazilian peppertree were generalists, and several were serious agricultural pests.

Miscanthus × giganteus is considered as a perspective energy crop for biomass production in Ukraine where its commercial production has been observed. The herbivorous pest may pose a risk of yield reduction when an energy crop is growing on monoculture. The herbivorous diversity, species composition and potential damage associated with growing M. × giganteus were studied on seven experimental sites at three locations in Ukraine. The different life stages of herbivorous insects from seven orders representing thirteen families were found on M. × giganteus during the herbivorous survey and most of the insects had a pest status. Research indicated that crop was an alternate host for key cereal pest the Hessian fly Mayetiola destructor (Say) (Diptera: Cecidomyiidae). A comparative analysis of the biodiversity of herbivorous insects across research locations was done using statistical analysis. It was found that site location played a significant role in the level of biodiversity and an increase in the insect’s herbivores diversity was associated with the type of researched lands. The massive scale commercial use of M. × giganteus should take into account a responsible consideration of the benefits and risks associated with that crop in order to protect agroecosystems.

As most vegetable growers know, plants have a lot of predators. Repetitive wounding events caused by herbivorous insects and necrotrophic pathogens often lead to tissue damage and growth restriction. When Arabidopsis ( Arabidopsis thaliana ) is subjected to recurrent wounding, leaf growth is

To understand the diveregence of herbivorous insects associated to plants, in terms of speciation, is useful to consider the evolutionary trends of the species, the geography and hystoricity of insect-plant interactions. In this chapter I will point out the major hypothesis in the speciation of herbivorous insects and describe a more integrative view of their speciation process, as an example, I will describe the results that I had obtained in the study of evolution of the weevils of the genus Trichobaris using several approaches, such as geometric morphometric, phylogenetics, and phylogeography. Finally, I conclude describing the trend in the evolution of this weevils.

The enemy-release hypothesis is one of the most popular but also most discussed hypotheses to explain invasion success. However, there is a lack of explicit, experimental tests of predictions of the enemy-release hypothesis (ERH), particularly regarding the effects of above- and belowground herbivory. Long-term studies investigating the relative effect of herbivores on invasive vs. native plant species within a community are still lacking. Here, we report on a long-term field experiment in an old-field community, invaded by Solidago canadensis s. l., with exclusion of above- and belowground insect herbivores. We monitored population dynamics of the invader and changes in the diversity and functioning of the plant community across eight years. Above- and belowground insects favoured the establishment of the invasive plant species and thereby increased biomass and decreased diversity of the plant community. Effects of invertebrate herbivores on population dynamics of S. canadensis appeared after six years and increased over time, suggesting that long-term studies are needed to understand invasion dynamics and consequences for plant community structure. We suggest that the release from co-evolved trophic linkages is of importance not only for the effect of invasive species on ecosystems, but also for the functioning of novel species assemblages arising from climate change.

Herbivorous insects have developed a series of behavioral responses to insecticides used in agricultural systems. The aim of the present study was to investigate behavioral changes in populations of diamondback moths exposed to areas treated with the oxine methylcarbamate insecticide. Populations of Plutella xylostella from the municipalities of Camocim de São Félix-PE (CSF), Sairé-PE (SR), Lajedo-PE (LJ) and laboratory populations: Recife-PE (RCF) and Viçosa-MG (VÇS) were exposed to dry residues of the insecticide in increasing doses. These populations had the behavioral parameters analyzed (Walking Distance (DC), Walking Time (DC), Average Speed ​​(VM), Number of Stops (NP) and Rest Time (TR)). Regarding CD, the populations of SR, CSF, LJ and VÇS did not show a clear pattern of reduction or increase of CD. The FHR population did not show any change in CD and differed statistically between studied areas. Regarding the TC parameter, the SR population showed an increase in this parameter, the FHR decreased and the other populations did not show a defined pattern. For Parameter VM, there was a reduction in the SR and CSF populations, and an increase in the MV in the FHR population. For the TR variable, the LJ, VSÇ and CSF populations did not present a definite pattern, therefore, the RCF population increased and SR reduced this parameter. Changes resulting from insect behavioral responses to insecticide-treated areas contribute to the poorer control effectiveness of insecticides as they are less exposed to lethal concentrations. Os insetos herbívoros tem desenvolvido uma série de respostas comportamentais para os inseticidas utilizados nos sistemas agrícolas. O presente estudo teve por objetivo averiguar alterações comportamentais de populações de traça-das-crucíferas expostas a áreas tratadas com o inseticida Metilcarbamato de oxina. Populações de Plutella xylostella provenientes dos municípios de Camocim de São Félix–PE (CSF), Sairé–PE (SR), Lajedo–PE (LJ) eduas populações de laboratório: Recife–PE (RCF) e Viçosa–MG (VÇS) foram expostas a resíduos secos do inseticida, em doses crescentes. Estas populações tiveram os parâmetros comportamentais analisados (Distância de caminhamento (DC),Tempo de caminhamento (DC), Velocidade Média (VM), Número de paradas (NP) e Tempo de Repouso (TR)). Em relação a DC, as populações de SR, CSF, LJ e VÇS não apresentaram padrão claro de redução ou aumento da DC. A população de RCF não apresentou alteração da DC e diferiu estatisticamente entre áreas estudadas. Em relação ao parâmetro TC, a população de SR apresentou aumento deste parâmetro, RCF diminuiu e as demais populações não demonstraram padrão definido. Para o Parâmetro VM, se verificou redução desta nas populações de SR e CSF, e aumento da VM na população de RCF. Para a variável do TR, as populações de LJ, VSÇ e CSF não apresentaram padrão definido, logo, a população do RCF aumentou e SR reduziu tal parâmetro. As alterações resultantes das respostas comportamentais dos insetos a áreas tratadas com inseticidas contribuem para uma menor eficácia de controle desempenhada pelos inseticidas, uma vez que estes vãos se exporem menos a concentrações letais.

This chapter presents information on the role of symbiotes in insect-plant interactions with emphasis on the endosymbiotes. Extracellular symbiotes between microorganisms and insects has developed both internally and externally in insects. The two most thoroughly studied groups of herbivorous insects which possess endosymbiotes are the Homoptera and Coleoptera. As in nonherbivorous insects, the presence of endosymbiotes in certain members of these herbivorous insects generally connotes a relatively restricted diet confined to one or two particular tissue-types of the host plant. Symbiotic microorganisms of beetles appear to be chief producers of an array of digestive enzymes which are capable of the hydrolytic breakdown of plant matrix polysaccharides. Most of the studies on the acquisition of digestive enzymes from saprophytic or mutualistic ectosymbiotic bacteria or fungi have been by Michael M. Martin and colleagues at the University of Michigan. The role of extracellular symbiotes associated with the alimentary tract of dipteran larvae and/or adults is only partially understood at present.

The shapes of plant leaves are remarkably diverse, but their ecological functions are largely unknown. Reports on the effects of leaf shape on biotic interactions such as herbivory are especially scarce, partly because herbivorous insects rarely rely on leaf shape for host selection. Here, we show that leaf shape acts as a physical deterrent against a leaf-processing herbivore. Plants in the genus Isodon (Lamiaceae) host a specialized leaf-rolling weevil (Apoderus praecellens) whose ovipositing females process an entire leaf into a leaf roll to serve as larval food and shelter. Among the species of Isodon, I. umbrosus var. hakusanensis is exceptional in that it has deeply lobed leaves. Because leaf processing follows a consistent sequence of complex behaviours, the unusual shape of I. umbrosus leaves may disrupt this process. Under both natural and laboratory conditions, female weevils preferred I. trichocarpus, a close relative with non-lobed leaves, over I. umbrosus. Nutritional properties of the leaves do not explain this preference because weevil larvae developed equally well on both hosts. Modifying the non-lobed I. trichocarpus leaves to mimic the shape of I. umbrosus leaves also discouraged leaf processing. Leaf processing often terminated because weevils failed to complete the inspection routine on I. umbrosus leaves. Leaf shape may be an important but overlooked factor that affects the interactions between plants and leaf-processing herbivores.

In their technical comment, Janz et al. take issue with our recent study examining the association between host breadth and diversification rates in the brush-footed butterflies (Lepidoptera: Nymphalidae) (Hamm and Fordyce 2015). Specifically, they are concerned that we misrepresent their "oscillation hypothesis" (OH) (Janz et al. 2006; Janz and Nylin 2008) and that one of our models was inadequate to test hypotheses regarding host breadth and diversification rate. Given our mutual interests in the macroevolutionary patterns of herbivorous insects, we appreciate the opportunity to respond to their concerns.

Conspecific individuals often exhibit behavioral differences that influence susceptibility to predation. Yet, how such trait differences scale to affect prey population regulation and community structure remains unclear. We used an 8 day field mesocosm experiment to explore the effects of intraspecific prey behavioral trait variation on survival in an herbivorous insect community. We further manipulated spider predator composition to test for top-down context-dependence of behavioral effects. Insect prey behavioral trait variance influenced survival through both direct (i.e., variation among conspecifics) and indirect (i.e., variation among heterospecifics) mechanisms. The behavioral variance of two prey species, Philaenus and Orchelimum, directly reduced their survival, though for Philaenus, this direct negative effect only occurred in the presence of a single spider predator species. In contrast, the survival of Scudderia was enhanced by the behavioral trait variance of the surrounding insect community, an indirect positive effect. Taken together, these results emphasize the importance of accounting for intraspecific variation in community ecology, demonstrating novel pathways by which individual-level behavioral differences scale to alter population and community level patterns.

Plants evolve diverse strategies to cope with herbivorous insects, in which the lipid-derived phytohormone jasmonic acid (JA) plays a crucial role. This study was conducted to investigate the differential responses of tomato and maize plants to Spodoptera exiguaherbivory and to clarify the role played by JA, methyl-jasmonate (MeJA) and jasmonoyl-L-isoleucine (JA-L-Ile) in their defense responses. JA, MeJA and JA-L-Ile were quantified using HPLC-MS/MS. The results showed that maize plant was more tolerant toS. exiguaherbivory than tomato. Spodopteraexigua attack induced JA, MeJA, and JA-L-Ile to high levels after 2 h of infestation in both test plants. Then, all studied JAsconcentration decreased gradually by increasing infestation time up to 1 week. JA concentration in infested maize was much higher than that in infested tomato leaves. However, MeJA concentration in infested tomato leaves was higher than that in maize. In control plants, JA was not recorded, while MeJA was recorded in comparable values both in tomato and maize. Our results showed that JA plays the main role in increasing defense responses to S. exigua infestation in the studied plants as a direct signaling molecule; however, MeJA could play an indirect role by inducing JA accumulation. JA-L-Ile indicated a less efficient role in defense responses to S. exigua attack in both test plants where its level is much lower than JA and MeJA.

Secondary plant metabolites such as those present in essential oils can be toxic to herbivorous insects and also repel attack, given they play a role in selection and acceptance of host plants. However, few studies have dealt with the use of plant-based repellents to manage invasive wasps. The objective was to assess essential oils with potential as wasp repellents, and to gain further insight as to how they affect the learning capacities of these insects. Five essential oils were tested on Vespula germanica (Fabricius) wasps in field choice and no-choice tests. When given a choice, foragers avoided the treated baits almost completely. Wind tunnel bioassays demonstrated that wasps recognise the repellent essential oils through olfactory cues, leading to a dose-dependent decreased response to the food stimulus. The effect of the repellents on the cognitive ability of V. germanica workers was also studied in relation to food search efficiency. Naive workers landed on the treated baits, although it took them longer than to land on control baits. When workers were allowed to forage on a food bait twice before a repellent was added, an effect on relocation behaviour was observed. The returning workers arriving to a feeding site with essential oil were reticent to land on it, suggesting that there is indeed a repellent effect and not just masking of the food source. A push–pull system combining attractive baits with the use of plant-based repellents is a promising management strategy in urban settings for this insect pest.

Experimental evolution has provided little support for the hypothesis that the narrow diets of herbivorous insects reflect trade-offs in performance across hosts; selection lines can sometimes adapt to an inferior novel host without a decline in performance on the ancestral host. An alternative approach for detecting trade-offs would be to measure adaptation decay after selection is relaxed, that is, when populations newly adapted to a novel host are reverted to the ancestral one. Lines of the seed beetle Callosobruchus maculatus rapidly adapted to a poor host (lentil); survival in lentil seeds increased from 2% to > 90% in < 30 generations. After the lines had reached a plateau with respect to survival in lentil, sublines were reverted to the ancestral host, mung bean. Twelve generations of reversion had little effect on performance in lentil, but after 25-35 generations, the reverted lines exhibited lower survival, slower development and smaller size. The most divergent pair of lines was then assayed on both lentil and mung bean. Performance on lentil was again much poorer in the reverted line than in the nonreverted one, but the lines performed equally well on mung bean. Moreover, the performance of the nonreverted line on mung bean remained comparable to that of the original mung-bean population. Our results thus present a paradox: loss of adaptation to lentil following reversion implies a trade-off, but the continued strong performance of lentil-adapted lines on mung bean does not. Genomic comparisons of the reverted, nonreverted and ancestral lines may resolve this paradox and determine the importance of selection vs. drift in causing a loss of adaptation following reversion.

15 pages; International audience; How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator-prey interactions to considering the full set of interacting species.

This chapter describes the ecology of foliar endophytes of the Acadian Forest that dominates Canada’s Maritime Provinces extending into Eastern Quebec and Maine. Recent evidence has illuminated the ‘foraging ascomycete’ life habit of fungi that can be endophytic in conifer needles. These fungi can occupy several eco-niches other than the needles including as saprophytes in aquatic or terrestrial environments or as endophytes of understory species. Structurally diverse secondary antifungal and antiinsectan metabolites appear to mediate the exchange between plant and fungus. The plant provides nutrients and shelter, the fungus increases plant fitness by contributing to tolerance to herbivorous insects or needle pathogens. This work is enabled by the advent of affordable sequencing capability, a dedication to fieldwork and alpha taxonomy, and directed investigations of the metabolites produced by these interesting fungi.

Plants can respond to insect egg deposition and thus resist attack by herbivorous insects from the beginning of the attack, egg deposition. We review ecological effects of plant responses to insect eggs and differentiate between egg-induced plant defenses that directly harm the eggs and indirect defenses that involve egg parasitoids. Furthermore, we discuss the ability of plants to take insect eggs as warning signals; the eggs indicate future larval feeding damage and trigger plant changes that either directly impair larval performance or attract enemies of the larvae. We address the questions of how egg-associated cues elicit plant defenses, how the information that eggs have been laid is transmitted within a plant, and which molecular and chemical plant responses are induced by egg deposition. Finally, we highlight evolutionary aspects of the interactions between plants and insect eggs and ask how the herbivorous insect copes with egg-induced plant defenses and may avoid them by counteradaptations.

Elevated ground-level ozone (O3) reduced C-based defense chemicals, however, severe grazing damages were found in leaves grown in the low O3 condition of a free air O3-concentration enrichment (O3-FACE) system. To explain this phenomenon, this study investigates the role of BVOCs (biogenic volatile organic compounds) as signaling compounds for insect herbivores. BVOCs act as scents for herbivore insects to locate host plants, while some BVOCs show high reactivity to O3, inducing changes in the composition of BVOCs in atmospheres with elevated O3. To assess the aforementioned phenomenon, profiles of BVOCs emitted from birch (Betula platyphylla var. japonica Hara) leaves were analyzed ex situ, and Y-tube insect preference tests were conducted in vitro to study the insect olfactory response. The assays were conducted in June and August or September, according to the life cycle of the adult alder leaf beetle Agelastica coerulea Baly (Coleoptera: Chrysomelidae). The Y-tube tests revealed that the leaf beetles were attracted to BVOCs, and O3 per se had neither an attractant nor a repellent effect. BVOCs became less attractant when mixed with highly concentrated O3 (&gt, 80 ppb). About 20% of the total BVOCs emitted were highly O3-reactive compounds, such as &beta, ocimene. The results suggest that BVOCs emitted from the birch leaves can be altered by elevated O3, thus potentially reducing the attractiveness of leaves to herbivorous insects searching for food.

Herbivorous insects may have significant impacts on litter decomposi- tion through modification of plant litter quality and quantity. The effects of herbivorous insects on decomposition processes are of growing interest. 2. Here, experiments were conducted to examine how sap-feeding aphids modify plant litter and whether the aphid-induced modification influences litter decomposition processes, using a plant-herbivore system consisting of soybean (Glycine max (L.)) and soybean aphids (Aphis glycines Matsumura). 3. First, litter traits produced by aphid-free and aphid-infected plants were compared, and it was found that aphids did not affect litter mass and carbon concentration, but significantly decreased the nitrogen concentration. Such aphid-mediated modification of litter quality may cause deceleration of litter decomposition as the higher C/N ratio inhibits litter decomposition. 4. A decomposition experiment was then carried out to compare the decomposition of litter between the aphid-free and aphid-infected plants. No impacts of aphid herbivory were found on litter carbon mineralisation but negative impacts were found on nitrogen mineralisation. Litter nitrogen mineralisation of aphid-infected plants decreased by 40% and 28% compared with that of aphid-free plants 1 and 3 months after commencement of the experiment, respectively. 5. The experimental results clearly showed that aphids decelerated litter nitrogen mineralisation by modifying litter quality.

Interactions among herbivores or between herbivores and other plant natural enemies, such as fungal pathogens, range from competition to facilitation. Moreover, the outcome of these interactions depends on the ecological context where they occur. In this study we examined the effects of clipping, as a surrogate of herbivory by ungulates, on the damage caused by two types of natural enemies (herbivorous insects and foliar fungal pathogens) on bilberry, Vaccinium myrtillus, in combination with nitrogen (N) fertilization representing current N atmospheric deposition. To examine whether the responses of both these natural enemies were mediated by changes in the plant, we estimated the effects of the treatments on bilberry growth and branching and on chlorophyll content as proxy of N content in leaves. Clipping increased the proportion of leaves damaged by herbivorous insects regardless of whether it was combined with N fertilization or not in 2008. In 2007 and 2009 repeated damage to the shrub also facilitated insect herbivory but only under N applications. Regarding fungal infestation incidence, clipping decreased the proportion of infected leaves in all the years considered but only in fertilized plots. Our results suggest that vertebrate herbivores facilitate insect herbivory and reduce fungal infestation but that these effects are dependent on nutritional conditions. Moreover, we found a negative residual correlation between insect herbivory and fungal infestation on bilberry leaves. Therefore, interactions between insect herbivores and fungal pathogens could be implicated in the final outcome of interactions between browsing ungulates and both bilberry natural enemies.

Predicting western corn rootworm (Diabrotica virgifera virgifera LeConte; WCR) development in the field depends on models that use experimentally determined degree-days (°D). For constant temperature regimes, this temperature sum can be reliably used to predict hatch and development of WCR larvae. In the first experiment in climate cabinets, we evaluated the effects of varying day–night (4 and 6 °C difference) temperature regimes compared to equivalent constant temperature regimes on hatch, development, and recovery of WCR larvae from a non-diapausing population. Relative to constant diurnal temperatures, varying day–night temperatures resulted in earlier larval hatch and accelerated larval development (especially when day–night temperatures differed by 6 °C) due to direct temperature effects (i.e., the Kaufmann-effect) and to enhanced plant growth. For WCR eggs, the temperature sums needed for hatch in the field are overestimated when they are determined by models based on constant experimental temperatures. Recovery of larvae from soil was not affected by temperature, but was positively associated with plant height. In a second experiment we evaluated whether the found effect of varying temperature ranges on the acceleration of larval hatch is also influenced by the level of these varying temperatures. Initial hatch started earlier by varying diurnal temperatures only under a low-temperature regime (14 ± 4 °C). For herbivorous insects like WCR, plant growth effects induced by varying temperature regimes may result in increased variation in temperature-based developmental parameters. Consideration of these effects will improve models that predict WCR hatching patterns and will improve the development and timing of control strategies.

Milkweed plants produce latex, which works as a defence against some herbivorous insects. The cerambycid beetles Tetraopes femoratus (LeConte) puncture the leaf midrib vein to extravasate the latex, and thus render the leaf edible. Nonetheless, it has not yet been investigated whether there is any further implication beyond food acquisition regarding this behaviour. The present study examined the hypothesis that leaf latex drainage is done mainly by females of T. femoratus, and that the males opportunistically prefer to feed on those ‘disarmed’ leaves. The experiments revealed that puncturing the leaf midrib vein to extravasate latex is done mainly by females of T. femoratus and not only serves their purpose of food acquisition, but also mediates an opportunistic feeding behaviour among males. Males of T. femoratus preferred to feed on milkweed leaves that had previously been fed upon by females. In addition, field observations showed that mating occurred more frequently on recently ‘disarmed’ leaves, suggesting increased copulation opportunities for females during leaf feeding. In sum, the results reveal that the feeding defence strategy of T. femoratusfemales to toxic milkweed foliage has created an opportunity for males to feed on milkweed leaves with a reduced risk of latex exposure and entanglement. Thus, this research provides empirical evidence of plant–insect interactions contributing to the appearance of an opportunistic adaptive feeding behaviour, which has broader implications for eco-evolutionary systems.

Herbivorous insects have been categorized as generalists or specialists depending on the taxonomic relatedness of the plants they use as food or oviposition substrates. The plasticity in host plant selection behavior of species belonging to the two categories received little attention. In the present work, fifth instar caterpillars of the generalist herbivore Helicoverpa armigera and its closely related species, the specialist Helicoverpa assulta, were fed on common host plants or artificial diet, after which their feeding preference was assessed individually by using dual - and triple- plant choice assays. Results show both the two Helicoverpa species have a preference hierarchy for host plants. Compared to the fixed preference hierarchy of the specialist H. assulta, the generalist H. armigera exhibited extensive plasticity in feeding preference depending on the host plant experienced during larval development. Whereas the specialist H. assulta exhibited a rigid preference in both dual and triple-plant choice assays, our findings demonstrate that the generalist H. armigera expressed stronger preferences in the dual-plant choice assay than in the triple-plant choice assay. Our results provide additional evidence supporting the neural constraints hypothesis which predicts that generalist herbivores make less accurate decisions than specialists when selecting plants.