Small or far away? Size and distance perception in the praying mantis

Area of Science:

• * Neuroethology and comparative vision research.
• * Investigating the evolution of sensory systems in insects.

Background:

• * Stereo vision, or 3D vision, is a complex trait found across diverse animal lineages, including primates, birds, and insects.
• * Potential evolutionary advantages include enhanced range finding, improved camouflage breaking, and accurate object size estimation.
• * The selective pressures driving the evolution of stereo vision remain an active area of research.

Purpose of the Study:

• * To determine if praying mantises utilize stereo vision to estimate prey size through disparity and angular size cues.
• * To test for size constancy, where an organism perceives an object's size as constant despite changes in its retinal image size due to distance.
• * To explore the role of 3D visual cues in the predatory behavior of mantises.

Main Methods:

• * A novel insect 3D cinema paradigm was employed to present virtual prey to praying mantises.
• * Virtual prey stimuli manipulated disparity cues (implying distance) and angular size cues.
• * The number of strikes by mantises was recorded as a measure of prey selection.

Main Results:

• * Mantises exhibited peak striking behavior when virtual prey implied a distance of 2.5 cm.
• * A significant decrease in strikes occurred as the implied distance increased beyond 2.5 cm.
• * No evidence of size constancy was observed; mantises did not preferentially strike prey of a specific physical size across simulated distances.

Conclusions:

• * Praying mantises do not appear to use stereo vision for estimating absolute object size or achieving size constancy.
• * The interaction between simulated distance and angular size suggests complex processing but not size constancy.
• * Evolutionary drivers for stereo vision in mantises likely stem from advantages other than precise size estimation, such as depth perception for capture.