Perception of solar UVB radiation by phytophagous insects: Behavioral responses and ecosystem implications

Most of our present knowledge about the impacts of solar UVB radiation on t errestrial ecosystems comes from studies with plants. Recently, the effects of UVB on the growth and survival of consumer species have begun to receiv e attention, but very little is known about UVB impacts on animal behavior. Here we report that manipulations of the flux of solar UVB received by fie ld-grown soybean crops had large and consistent effects on the density of t he thrips (Caliothrips phaseoli, Thysanoptera: Thripidae) populations that invaded the canopies, as well as on the amount of leaf damage caused by the insects, Solar UVB strongly reduced thrips herbivory. Thrips not only pref erred leaves from plants that were not exposed to solar UVB over leaves fro m UVB-exposed plants in laboratory and field choice experiments, but they a lso appeared to directly sense and avoid exposure to solar UVB, Additional choice experiments showed that soybean leaf consumption by the late-season soybean worm Anticarsia gemmatalis (Lepidoptera: Noctuidae) was much less i ntense in leaves with even slight symptoms of an early thrips attack than i n undamaged leaves. These experiments suggest that phytophagous insects can present direct and indirect behavioral responses to solar UVB, The indirec t responses are mediated by changes in the plant host that are induced by U VB and, possibly, by other insects whose behavior is affected by UVB.