Table of Contents

17 August 2012
Vol 337, Issue 6096

About The Cover

Cover image expansion

COVER Male rhinoceros beetles (Trypoxylus dichotomus) wield a huge forked horn on their heads. Sexual selection may favor the evolution of exaggerated trait sizes because the developmental mechanism responsible for increased growth also results in signal reliability. See page 860. Photo: Will Freihofer and Douglas Emlen