Response of the Praying Mantis, Sphodromantis Viridis, to Target Change in Size and to Target Visual Occlusion

Abstract

Mantises (Mantodea, Mantidae) visually detect insect prey and capture it by a ballistic strike of their specialized forelegs. We tested predatory responses of female mantis, Sphodromantis viridis, to computer generated visual stimuli, to determine the effects of (i) target size and velocity (ii) discrete changes in target size and (iii) visual occlusion. Maximal predatory responses were elicited by stimuli that (i) subtended ~20°–23° horizontally and ~16°–19° vertically, at the eye, and moved across the screen at angular velocities of ~46°–119°/s, (ii) increased in size in a stepwise manner, with step duration ≥0.8 s, while stimuli decreasing in size elicited only peering movements, (iii) Stimuli disappearing gradually behind a virtual occlusion elicited one or more head saccades but not actual interception.