Investigating how UV radiation affects egg parasitoid fitness and behavior

Insects navigate highly variable conditions of exposure to ultraviolet (UV) radiation, which can have physiological and behavioral effects on their fitness. Accordingly, integrated pest management strategies that manipulate UV exposure are being developed to exploit agricultural pests’ attraction to UV radiation and susceptibility to UV damage. Considering the lack of knowledge on how such techniques could affect their natural enemies, we studied the influence of UV radiation across the lifecycle of two egg parasitoid species: Telenomus podisi and Trissolcus utahensis (Hymenoptera: Scelionidae). Using UV lamps and UV-filtering materials, we conducted multiple laboratory and field experiments to examine parasitoid life history parameters, host location and exploitation. We show that UV radiation can have negative consequences on parasitoid fitness, as long-term exposure of immature and mature individuals to mild UV intensities reduced their emergence and longevity. We also describe behavioral responses to UV radiation, as UV-microhabitats were attractive to foraging females but also reduced their walking activity. Nonetheless, we observed a high parasitism rate under UV-attenuated macrohabitats in field cages. During host selection and protection, females did not discriminate for photoprotective quality, as revealed by brood guarding videos and choice tests between egg masses placed under different UV exposure conditions. However, maternal investment was higher in less phototoxic conditions as females spent more time protecting progeny under UV-attenuated microhabitat (leaf bottom) in the field. Together, these different experimental approaches provide important insight on the complex relationship between beneficial insects and an understudied abiotic factor that is both environmental hazard and visual cue.