Description:
Summary Foraging is a result of innate and acquired mechanisms, and is optimized in order to increase fitness. During foraging an animal faces many threats - such as predation and infection. The uptake of parasites and diseases while foraging is common and an individual should be adapted to detect and avoid such threats, using cues either from the abiotic environment, or the parasite. Social animals possess an additional cue to detect such contaminated food sources: information provided by conspecifics. Bumblebees avoid contaminated flowers, but the cues used by the bees to distinguish contamination remain unknown. We tested under controlled laboratory conditions the use of scent marks derived from other foragers in choosing between a contaminated and uncontaminated flower. As a positive control we tested the bees' choice towards two flowers, one scented with geraniol and including a highly rewarding sugar solution and the other not scented and containing a poorer reward. The bees mainly chose the uncontaminated and the rewarding scented flower. Scent marks did not increase the efficiency of the bumblebees in choosing the better flower. The bees from both experiments behaved similarly, showing that the main and most relevant cue used by them to choose the uncontaminated flower is the odour from the parasite itself. The adaptation of bumblebees to avoid flowers contaminated by Crithidia bombi, arose from the long term host-parasite interaction between these species. This strong adaptation results in an innate behaviour of bees and a detection and aversion of the odour of contaminated flower nectar.