Protean behaviour of a neustonic insect: factors releasing the fright reaction of whirligig beetles (Coleoptera: Gyrinidae)

Abstract

Whirligig beetles are common neustonic insects whose response to approach of any object is a rapid, irregular swimming. We recorded the incidence of swimming and diving of individual Gyrinus pleuralis Fall in response to the movement of black and white circular models. The frequency of response increased with model size up to 5 cm diameter beyond which no increase occurred. Swimming occurred more often in response to black models. The role of this response in a more comprehensive antipredator stategy is considered.