Mathilde Gaudreau

Université de Montréal
Shedding UV light on brood guarding parasitoids Mathilde Gaudreau,

Paul K. Abram & Jacques Brodeur

Some parasitoid wasps engage in lengthy maternal care behavior to defend their progeny against predators and parasites. Because parasitoids that exploit immobile hosts like insect eggs must endure a range of local environmental conditions, investment in brood guarding is expected to vary according to the effect of microhabitat quality on both maternal and offspring fitness. Parasitoid perception of potentially damaging abiotic factors such as ultraviolet (UV) light could affect brood guarding behavior and its resulting impact on offspring survival and the success of biological control programs. Despite the ubiquity of UV light in nature, its influence on insect behavior (e.g. host selection and exploitation) has been neglected. Using female stink bug egg parasitoids Telenomus podisi and Trissolcus cosmopeplae – known for staying on parasitized host egg masses for up to 24 h – we performed the first extensive observations of brood guarding behavior in the field under naturally distinct UV light environments (leaf top/bottom). The presence of a female parasitoid on Podisus maculiventris host egg masses placed on soybean plants was checked every 20 minutes for 8 h and then once after 24 h. We showed that brood guarding duration was reduced on leaf tops with species-specific effects and tended to be overestimated in laboratory settings restricting parasitoids to confined conditions in Petri dishes. As UV-blocking materials are becoming more prevalent in agricultural practices, we highlight the importance of using realistic settings to test behavioral responses of natural enemies to this important environmental factor.