The visual field of swarming male Episyrphus balteatus (Diptera: Syrphidae).

摘要

One of the challenges faced by swarming Diptera is that of detecting and identifying an approaching flying insect on the basis that it may present a potential mating opportunity. This paper discusses the measurement of the visual field and orientation changes exhibited by males of the common swarming hoverfly Episyrphus balteatus (De Geer). The visual field extended 320 degrees in the horizontal plane and 315 degrees in the vertical plane. The probability of detecting an approaching flying insect was an estimated 0.97. Members of the swarm turned 25 degrees at each change in orientation. Changes in orientation are a proposed method of placing an approaching insect within the visual field of the dorsal fovea for early recognition. This enables male E. balteatus to initiate a chase without the reaction response and consequent delay which would otherwise occur.