Adult female exposure to mild ultraviolet radiation reduces longevity but not egg load in two parasitoid wasps

Insects can be exposed to ultraviolet (UV) radiation throughout their lifecycle when they rest, forage, and mate. The negative effects that such highly energetic photons can have on insect fitness are not well-known, especially for natural exposure during the adult stage. Adult insects are considered to be more resistant to UV radiation than their immature stages, but this assumption is supported by only a few studies on a restricted set of pest species. We conducted the first investigation of the vulnerability of parasitoid adults to UV exposure, by assessing the longevity and potential fecundity of female Telenomus podisi Ashmead and Trissolcus utahensis Ashmead (Hymenoptera: Scelionidae) receiving low doses of UV-A and visible radiation daily in the laboratory. Parasitoids died up to 2x faster with increasing levels of UV radiation, and, to a lesser extent, of visible radiation. There was no effect of UV radiation on maximum egg load resulting from oogenesis in early adulthood. This study on beneficial insects indicates that the physiological consequences of cumulative exposure to even mild doses of more energetic optical radiation, particularly in the UV range, should not be underestimated in natural and managed ecosystems.