Credit: SCIENCE/AAAS

Science 323, 773–776 (2009)

Among many insects there are two male types, dominant and subordinate. But researchers studying the horns of dung beetles have found that some species have three types.

Mark Rowland at the University of New Mexico in Albuquerque and Douglas Emlen at the University of Montana in Missoula trapped and studied closely related dung beetles, the phanaeine. They noticed that males could have big horns, little horns or no horns at all. Some species had a developmental mechanism that entirely halted horn growth in subordinates, and others had one that merely attenuated horn growth. Five species had both — resulting in alpha, beta and gamma males (pictured, clockwise from top right: female, gamma, beta and alpha).