Theory on condition-dependent risk-taking indicates that when prey are in poor condition, their anti-predator responses should be weak. However, variation in responses resulting from differences in condition is generally considered an incidental by-product of organisms living in a heterogeneous environment. Using Leptinotarsa decemlineata beetles and stinkbug (Podisus maculiventris) predators, we hypothesised that in response to predation risk, parents improve larval nutritional condition and expression of anti-predator responses by promoting intraclutch cannibalism. We showed that mothers experiencing predation risk increase production of unviable trophic eggs, which assures provisioning of an egg meal to the newly hatched offspring. Next, we experimentally demonstrated that egg cannibalism reduces L. decemlineata vulnerability to predation by improving larval nutritional condition and expression of anti-predator responses. Intraclutch cannibalism in herbivorous insects might be a ubiquitous strategy, aimed to overcome the dual challenge of feeding on protein-limited diets while living under constant predation threat.

BACKGROUND: Cultivation of grapes is a major crop globally, particularly in support of the wine production industry which has significant economic impact in numerous countries. Sour rot is an economically important disease of grapes. It is caused by an interaction of yeast + acetic acid bacteria, and vectored by Drosophila spp. Substantial control of sour rot in wine grape vineyards has been achieved by control of Drosophila using insecticides such as zeta-cypermethrin. An outbreak of sour rot and high populations of Drosophila melanogaster were observed in 2018 in a vineyard in New York (Finger Lakes region), USA. Flies from this population were found to be resistant to zeta-cypermethrin (the active ingredient in Mustang Maxx®), but whether or not this was a widespread problem was not known. To determine if resistance was geographically limited, we surveyed populations of D. melanogaster collected from 11 vineyards across New York State and one in Missouri (USA). We also evaluated 19 alternative insecticides for their potential use for control of D. melanogaster, by determining their toxicity to a susceptible strain and by examining cross-resistance using a field-collected population.RESULTS: There were high levels of resistance to zeta-cypermethrin, malathion, and acetamiprid found in all populations sampled. Resistance to zeta-cypermethrin and malathion was stable over 33 months. Results from two vineyards also suggested that resistance to spinetoram was starting to evolve. The alternative insecticides we evaluated had LC 50 values to the susceptible strain ranging from 0.65 to 15 000 ng•cm −2 . CONCLUSION: Resistance to zeta-cypermethrin, malathion, and acetamiprid is geographically widespread and the levels of resistance are similar between early season and late season collections. Cross-resistance was detected against all the insecticides tested, with the lowest levels seen for broflanilide, fipronil, and flumethrin. These patterns of resistance/cross-resistance/multiple resistance are discussed in terms of selection within and outside of vineyards. The implications of these results to insecticide resistance monitoring and management are discussed.

1. Maternal provisioning can reduce offspring vulnerability to predators by promoting offspring growth and eliciting of antipredator behaviours. Mothers perceiving predation risk may improve offspring survival if producing larger, higher‐quality offspring. However, empirical evidence suggests that offspring quality is often reduced, probably reflecting predator‐induced physiological costs, or a selfish maternal strategy aimed at producing more offspring by sacrificing their quality. While perception and impact of predators can vary across the prey's life stage, a majority of studies have focused on understanding how reproductive allocation decisions are influenced by the risk of predation during adulthood. 2. In this study, Leptinotarsa decemlineata beetles were used to examine if the risk of predation during the larval stage: (i) impacts the mother's physiological condition, including body mass and metabolic rate; and (ii) alters maternal allocation of reproductive resources to offspring quantity versus quality. 3. Results revealed that L. decemlineata mothers responded to perceived predation risk by producing clutches with fewer but larger eggs, thus increasing offspring provisioning. Surprisingly, while females that had faced predation risk as larva emerged with a similar body mass to control females, they exhibited lower metabolic rates. 4. Although predation risk in L. decemlineata larvae is known to impair their ability to acquire and maintain energy resources, adult females appeared to ameliorate such costs by improving their metabolic efficiency and by allocating more of their limited reproductive resources to produce fewer but better‐quality offspring.

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