Parental Effects of Insecticide Use Frequency on Fluctuating Asymmetry in the European Earwig Forficula auricularia s.l.

We measured fluctuating asymmetry (FA) on seven morphometric traits in unexposed progeny of Forficula auricularia mothers sampled in orchards ranging from no insecticide use to frequent applications. Among these traits, tibia, femur, and elytra lengths showed consistently higher fluctuating asymmetry in offspring from insecticide-treated orchards, with median asymmetry approximately 50% higher in IPM and twice as high in conventional orchards than in organic orchards. No difference was observed in forceps measurements, suggesting the development of this fitness-related structure in earwigs may be buffered against insecticide effects. Measuring FA in locomotor appendages of progeny from parents originating from agroecosystems may represent a reliable and easy-to-use tool to monitor the environmental effects of insecticides.