A size continuum of 8 similarly-shaped species of tiger beetles,Cicindelaspp., with dark or orange abdomens was presented to wild, female robber flies of the speciesEfferia tricella(Bromley). A significant inverse correlation between prey size and attack rate was found. In addition, medium sized tiger beetles (surface area = 86 mm2) with orange abdomens were attacked 13–18% less frequently than were medium sized tiger beetles with dark abdomens. However, small tiger beetles (surface area = 53 mm2) with orange abdomens were attacked only 7% less frequently than were small tiger beetles with dark abdomens.