PREY CAPTURE BY DRAGONFLY LARVAE (ODONATA; ANISOPTERA)

Abstract

Dragonfly larvae catch prey by rapid protraction of a curiously modified labium. There are two main types of predatory behavior; 'climbers' move amongst aquatic vegetation and use their large compound eyes to detect prey at a distance and subsequently to orient towards it, while 'sprawlers' live at the bottom and detect most of their prey by tactile stimulation. Five species of dragonfly larvae were successful in 60 to 70% of their attacks on mosquito larvae, but in only 25 to 28% on gammarids. Size and movement of prey are important in its recognition, while shape, color, and odor are not. The forward thrust of the labium takes only 15 to 20 milliseconds, and at the time of the strike the anal siphon is closed so that the blood pressure, which provides the force for labial extension, is all directed forwards and is not used to expel water from the colon.