It’s just amazing how nature can shape insect appendages and forms in the race for cometition. In a New York Times article entitled Extravagant Results of Nature’s Arms Race Nicholas Wade wrote:
Competition among males is often expressed in the form of elaborate weapons made of bone, horn or chitin. The weapons often start off small and then, under the pressure of competition, may evolve to attain gigantic proportions.
This is indeed an interesting article and many samples of beetles, predominantly Scarabs and genus Onthophagus, are shown in the accompanying slideshow.
Dynastinae and several subfamilies of Scarabaeidae and Lucanidae have these armaments. In the Philippines, we also have several species of which Chalcosoma atlas LINNAEUS 1758 is a prime example. Xylotrupes gideon philippinensis ENDROEDI 1957, Theodosia rodriguezi NAGAI 1980 (right) and several species of Onthophagus are just a few other species. And of course, stag beetles, family Lucanidae, are one of the most spectacular.
Note: Thanx to Armand Frasco for sending me the link. Top photo from NY Times website is Onthophagus (Proagoderus) rangifer.