Cycloalexy

Definition

A pre-emptive, tight circular grouping behavior exhibited by gregarious immature insects in which individuals arrange themselves in a ring with heads oriented either toward or away from the center. Unlike predator-induced defenses, cycloalexy occurs during rest and serves as a passive, collective shield against detection or attack.

Etymology

Greek kyklos (circle) + alek- (to defend), coined 1988 by entomologists João Vasconcellos-Neto and Pierre Jolivet

Example

Nymphs of the tortoise beetle Acromis sparsa form tight cycloalexy rings on host-plant stems, with heads outward presenting a perimeter of spiny shields; some sawfly larvae rest in heads-inward circles that conceal vulnerable body regions.

Related Terms

• gregariousness
• collective defense
• resting behavior
• predator avoidance
• nymphal aggregation

Usage Notes

Originally defined to include both heads-inward and heads-outward orientations, though subsequent authors have debated whether stricter criteria (e.g., mandatory heads-outward posture) should apply. Distinguished from predator-responsive behaviors such as thanatosis or startle displays by its occurrence during undisturbed rest. The term applies specifically to circular formations; linear or irregular aggregations do not qualify.