Fig. 1.

Variation in horn morphology and fighting styles in rhinoceros beetles. (A) Trypoxylus dichotomus males have a long, forked head horn that is used like a pitchfork to lift and twist opponents off tree trunks during fights. (B) Dynastes hercules males have a long head horn and long thoracic horn that are used together similar to pliers to lift, squeeze, and then toss opponents to the ground. (C) Golofa porteri males have a long, slender head horn that is used similar to a fencing sword to both lift opponents off narrow shoots and push them sideways off balance. Vectors represent the typical forces experienced by horns during fights: vertical bending (red), lateral bending (blue), twisting (green). Illustrations by David J. Tuss.