The influence of floral character on the foraging behaviour of the hoverfly, Episyrphus balteatus

A bioassay to examine the foraging behaviour of the aphidophagous hoverfly, Episyrphus balteatus was used in which various stimuli purported to influe nce flower choice were tested using model flowers. In choice experiments, E . balteatus exhibited enhanced behavioural responses to the colour yellow, as previously seen in Eristalis by several workers. Previous suggestions th at the generalist forager E. balteatus has no preference for colour are re- examined in the light of this new evidence. The other advertisement cue tes ted, size, was also demonstrated to play an important role in determining f oraging behaviour, with the smaller artificial flowers seemingly preferred. Of the rewards tested, E. balteatus showed preference for the greatest nec tar concentrations, whilst increasing pollen did not affect behaviour. Thes e bioassays provided an opportunity to isolate the individual components of decision-making by E. balteatus during foraging. The separation of sexes a nd ages in these experiments permitted analysis of inter-sexual and inter-g eneration differences in behaviour, a factor apparently not investigated in previous work.