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It is known that many social insects and arthropod predators and parasitoids can learn the association between a resource and volatile cues. Although there are various studies on the effect of experience in immature arthropods on behavior later in adult life, not much is known about the effects of such experiences on immature behavior. This was investigated here in the lacewing Ceraeochrysa cubana (Hagen) (Neuroptera: Chrysopidae). Whereas adults of this lacewing feed on plant‐provided food and honeydew, larvae are voracious polyphagous predators of several insect pests, and therefore important for biological control. Hence, studying the foraging behavior and the effects of learning in immatures of this species is important. We exposed immatures to the volatile methyl salicylate (MeSA), which was either associated with food or with the absence of food. Subsequently, their response to this volatile was tested in an olfactometer. Immatures that had experienced the association of MeSA with food were attracted to it and immatures that were exposed to MeSA during food deprivation were repelled. Subsequently, predator immatures that had experienced the association between MeSA and food were released on a plant without food and were found to use this volatile in locating patches with food. In contrast, larvae without such experience were found equally on food patches with and without the volatile. We conclude that these immature predators are capable of learning the association between volatiles and food, or the absence of food, and use this during foraging.

Jasmonates such as jasmonic acid (JA) are plant-signaling compounds that trigger induced resistance (IR) to a broad range of arthropod herbivores. JA-dependent defenses are known to reduce the growth and survivorship of many chewing insects, but their impact on piercing‐sucking insects such as aphids has not been extensively investigated. In this study, induced resistance was activated in tomato ( Lycopersicon esculentum Mill) (Solanaceae) using a foliar application of synthetic JA, and control plants were treated with carrier solution. The life parameters of individual potato aphids and their progeny ( Macrosiphum euphorbiae Thomas) (Hemiptera: Aphididae) were evaluated on the unsprayed leaves of plants in order to access the systemic effects of the foliar treatments. IR significantly reduced the longevity and net reproduction of adult aphids, as well as the percentage of juveniles to survive to maturity. These results indicate that JA application induces systemic defenses in tomato that have a direct negative impact on aphid survivorship. This study also examined aphid honeydew excretion, in order to evaluate the potential influence of induced resistance on aphid feeding behavior. The average honeydew production per aphid was comparable on plants with or without JA treatment, indicating that JA-dependent defenses did not deter feeding. This suggests that the observed effects of JA on aphid survivorship were due to antibiotic rather than antixenotic factors. In addition to studying the effects of JA treatment on a tomato cultivar that is susceptible to aphids, this study also examined the effects of exogenous application of JA on tomato plants that carry the aphid resistance gene, Mi-1.2 . JA application did not significantly enhance or inhibit aphid control on resistant tomato. These findings expand our understanding of the effects of JA-dependent defenses on piercing‐sucking insects, and of the potential interactions between induced resistance and R-gene mediated aphid resistance in tomato.

Parasitoids as well as many of their herbivorous hosts, depend on carbohydrate-rich food during the adult stage. Different types of nectar and honeydew vary with regard to their sugar composition. In order to successfully exploit a food source, the insect must show a positive gustatory response to its component sugars and be able to digest and metabolise them. Here we tested the herbivore Plutella xylostella L. (Lepidoptera: Plutellidae) and its parasitoid Diadegma semiclausum (Hellén) (Ichneumonidae: Campopleginae) with respect to their feeding response and longevity when provided with one of nine sugars (fructose, glucose, lactose, maltose, melibiose, melezitose, raffinose, sucrose, or trehalose). Both species responded to and showed a prolonged life span on a broad range of sugars. The impact of food supply on life span was about sixfold higher for the parasitoid than for the herbivore. In general, there was a good fit between gustatory response and achieved longevity, with some outliers. Both species showed only weak responses to melibiose, which significantly prolonged life span. The parasitoid showed a gustatory response to melezitose, which did not prolong its life span. The parasitoid and its herbivorous host responded differently to trehalose. These differences in gustatory response and longevity show the potential for application of selective sugar sources in conservation biological control. At the same time it also reveals a risk that the indiscriminate application of sugar sources may stimulate herbivory. [KEYWORDS: herbivore ; selectivity ; food supply ; conservation biological control ; Lepidoptera ; Plutellidae ; Ichneumonidae ;Campopleginae]

The host-discrimination behavior of two species of phloem-feeding membracid nymphs was examined through pair-wise choice experiments using whole twigs, leaf extracts and sap exudates. Both species have restricted host ranges in the field: Vanduzeea arquata is monophagous, while Enchenopa binotata may best be considered narrowly oligophagous in that it represents a complex of sympatric, reproductively isolated populations each associated with a different species or genus of plants. Nymphs of both species settled preferentially on twigs of their respective host plants but those of V. arquata showed absolute discrimination while those of E. binotata selected the alternative twigs a small percentage of the time. Vanduzeea arquata nymphs also showed a greater sensitivity to plant extracts, as a larger proportion of their responses, both positive and negative, were significant. Leaf extracts of all plants tested discouraged ingestion but not probing, and most nymphs exhibited a positive probing response to the extracts of their respective hosts. Only the sap exudates of the hop-tree (Ptelea trifoliata) inhibited ingestion. Enchenopa binotata nymphs from the population associated with the hop-tree also showed a negative response to these extracts but only at a higher concentration. Water-soluble quaternary alkaloids are the secondary metabolites of the hop-tree most likely to be present in the extracts used in this study and in the phloem sap of the plant. They also occur in the honeydew of nymphs feeding on this species. Because these compounds are known to be cytotoxic, it is likely that hop-tree E. binotata nymphs possess physiological specializations to detoxify or tolerate them. RESUME Comportement de selection de l'hote par les larves de Vanduzeea arquata et des especes du complexe Enchenopa binotata (Homoptera: Membracidae): distinction des pousses saines, des extraits de feuilles et d'exsudats de seve Les larves de Vanduzeea arquata Say et de 3 membres du complexe Enchenopa binotata Say preferent legerement plus les pousses des especes de leurs hotes respectifs dans des choix binaires. Les reponses (alimentation et sondage) des larves a des extraits de feuille et a des exsudats de seve d'especes de plantes hotes ou non ont ete examinees avec des sachets a couche simple ou double de parafilm. Les extraits de feuille de plante hote stimulaient le sondage par beaucoup de larves. Les extraits de feuille et de seve de Ptelea trifoliata (Rutacees) inhibaient la prise de nourriture des larves de toutes les especes, mais l'effet dissuadant etait moins prononce sur les larves des especes d'Enchenopa associees a cet arbre que sur les autres. La presence d'alcaloides quaternaires dans le phloem de cet arbre peut dissuader les autres larves de membracides de s'alimenter sur cette essence, mais ces substances ont ete decelees dans les larves d'Enchenopa et dans leur miellat. Des glucosides flavonoides, presents dans les extraits de feuille et les exsudats de seve de Robinia pseudoacacia (Fabacees) et de Celastrus scandens et C. orbiculatus (Celastracees), n'ont pas modifie significativement le comportement alimentaire des larves d'Enchenopa, mais peuvent avoir influence celui des larves de V. arquata. Les larves d'Enchenopa presentaient une plus faible aptitude que les larves de V. arquata a choisir leur hote; leur tolerance relative pour des especes non hotes peut ětre liee a la speciation en fonction de la filiation de vegetaux qui semble avoir eu lieu dans ce groupe.