Eye morphology, visual orienting, and responses to stationary prey objects by the praying mantis, Euchomenella macrops

Euchomenella is a genus of praying mantis (Insecta: Mantodea) restricted to Asia (including India) which inhabits shrubbery and trees. Euchomenella macrops has many unique morphological and behavioral characteristics. Those of particular interest are (1) the unique morphology of its compound eyes and the resultant extent of its binocular visual field, (2) its unusual propensity to strike at stationary prey objects, and (3) the relationships between its head and prothorax movements during visual orientation, fixation, and tracking of prey. Eye morphology was analyzed with computer measuring software techniques applied to enlarged digitized micrographs. Visually elicited behaviors were assessed via frame-by-frame analyses of video recordings. In these experiments, tethered female mantises viewed computer generated visual stimuli designed to simulate key aspects of prey objects. Compound eye morphology is such that E. macrops’ binocular visual field is as much as 25% larger than that of more well known species such as Tenodera sinensis. Unlike other species, E. macrops will readily strike at prey objects many seconds after they have stopped moving; this is often preceded by orienting movements in which the head and prothorax pivot in opposite directions so as to keep the head parallel to the frontal visual plane.