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Abstract More than 30% of human food crop yield requires animal pollination. In addition, successful crop production depends on agrochemicals to control pests. However, agrochemicals can have negative consequences on beneficial insect pollinators, such as bees. We investigated the effects of an emerging class of pesticides, sulfoximines, on the common eastern bumblebee, Bombus impatiens. We performed a series of 96-hour toxicity tests on microcolonies of laboratory-reared B. impatiens. Our data showed that sulfoxaflor (SFX) is significantly less toxic to B. impatiens than historically used neonicotinoid pesticides, such as thiamethoxam. Further, for the first time, we found significant differences among castes in sensitivity to SFX; workers and drones were more sensitive than queens. These findings are notable because they reveal both caste and sex-specific differences in bumblebee sensitivity to pesticides. Interestingly, we found no evidence that bumblebees avoid SFX-contaminated sugar syrup. To the contrary, B. impatiens workers had an apparent preference for SFX-contaminated sugar syrup over sugar syrup alone. Overall, our investigation provides novel information on an important pesticide and may help inform regulatory decisions regarding pesticide use. 

Females of many species are polyandrous. However, polyandry can give rise to conflict among individuals within families. We examined the level of polyandry and paternity skew in the common eastern yellowjacket wasp,Vespula maculifrons, in order to gain a greater understanding of conflict in social insects. We collected 10 colonies ofV. maculifronsand genotyped workers and prereproductive queens at highly variable microsatellite markers to assign each to a patriline. Genotypic data revealed evidence of significant paternity skew among patrilines. In addition, we found that patrilines contributed differentially to caste production (worker vs. queen), suggesting an important role for reproductive conflict not previously discovered. We also investigated if patterns of paternity skew and mate number varied over time. However, we found no evidence of changes in levels of polyandry when compared to historical data dating back almost 40 years. Finally, we measured a suite of morphological traits in individuals from the most common and least common patrilines in each colony to test if males that showed highly skewed reproductive success also produced offspring that differed in phenotype. Our data revealed weak correlation between paternity skew and morphological phenotype of offspring sired by different males, suggesting no evidence of evolutionary tradeoffs at the level investigated. Overall, this study is the first to report significant paternity and caste‐associated skew inV. maculifrons, and to investigate the phenotypic consequences of skew in a social wasp. Our results suggest that polyandry can have important consequences on the genetic and social structure of insect societies.