The role of escape in mimicry and polymorphism: I. The response of captive birds to artificial prey

The effectiveness of active escape as an alternative to chemical and physical irritants in defensive mimicry was tested. Philaenus spumarius is a polymorphic insect used to illustrate the hypothesis that an efficient escape mechanism could be associated with conspicuousness by potential predators causing them to avoid this type of prey. Tile experiment used robins (Erithacus rubecula) as predators and mealworms {Tenebrio mulilur), with colour bands of either green, orange or blue, as prey. To simulate escape the prey was offered from a lunged platform which could be dropped allowing the mealworm to roll away and out ol'sigln of the bird before it could be pecked. During the first half of the experiment (day 1–10) only one of the tin ee colours of mealworm was allowed to be caught, within a 180 s time limit. This was a cryptic non-mimetic (blue) form. The other two were the cryptic (green) and conspicuous (orange) escaping models. In the second half of the experiment (day 11–17) the platform was not lowered within the lime limit. The three forms of prey remain available; the models thus becoming the mimics. During the first part of the experiment the birds took the non-mimetic form Ireely and learned to avoid the conspicuous and to a lesser degree the cryptic models. Throughout the second pan of the experiment the conspicuous form continued to be avoided more than the cryptic, illustrating the greater efficiency of conspicuous colour combined with escape.