Visual stimuli that elicit visual tracking, approaching and striking behavior from an unusual praying mantis,...

Area of Science:

• * Entomology
• * Ethology
• * Visual Ecology

Background:

• * Euchomenella macrops possesses distinct morphological traits: a smaller head, shorter foreleg tibia, and longer prothorax.
• * These features are hypothesized to be adaptations for capturing smaller, slower prey compared to other mantis species.
• * Previous research suggests specialized predatory adaptations in mantis species.

Purpose of the Study:

• * To test the conjecture that Euchomenella macrops is specialized for smaller, slower prey.
• * To assess the influence of visual stimulus characteristics (size, speed, color, shape) on predatory behaviors (tracking, approaching, striking).
• * To analyze the kinematic basis of visual tracking in E. macrops.

Main Methods:

• * Computer-generated visual stimuli (disks, rectangles) with controlled size, speed, color, and movement patterns were presented to adult female E. macrops.
• * Predatory responses, including visual tracking, approaching, and striking, were recorded and quantified.
• * Stimulus parameters such as visual angle, speed (deg/s), and color (red, blue, green, grey) were systematically varied.

Main Results:

• * Strike rates varied with stimulus size and speed; larger, faster disks (up to 44 deg at 143 deg/s) or smaller disks at slower speeds (<27 deg at 113-127 deg/s) were preferred for erratic movement.
• * E. macrops consistently struck at small (5 deg) stationary disks after linear movement from the periphery.
• * Higher strike rates were observed for red disks (23 deg) compared to blue or green, despite equal tracking rates across colors. Elongated stimuli elicited more approaching but not striking.
• * Tracking behavior predominantly involved head rotation rather than prothorax rotation.

Conclusions:

• * Euchomenella macrops demonstrates a complex and size-dependent predatory response to visual stimuli, supporting the hypothesis of specialization for smaller prey.
• * Prey size and movement dynamics significantly influence strike behavior, with distinct preferences for speed and size.
• * Color perception plays a role in prey selection, with a preference for red stimuli, and predatory movements are primarily driven by head rotation.