Exploitative competition for floral resources reduces sugar intake but differently impacts the foraging behaviour of two non-bee flower visitors

Identifying which behavioural strategies maximize individual fitness is a key objective in ecology. Organisms are known to adapt their foraging behaviour to their environment in response to abiotic and biotic constraints, such as the distribution of resources or the presence of competitors. For instance, bees are known to avoid recently visited flowers and thus focus their foraging on more rewarding patches. Whether other flower-visiting insects adapt their foraging behaviour in response to exploitative competition for floral resources remains unknown. Here, we asked if a predatory hoverfly (Episyrphus balteatus) and a parasitoid (Aphidius colemani) 1) are physiologically impacted by flower resource limitation following exploitation of flowers by a competitor (either the bumblebee Bombus terrestris or E. balteatus); 2) have the ability to discriminate flowers that were previously exploited by a competitor; and 3) modify their foraging behaviour accordingly. Episyrphus balteatus and A. c...