Rhinoceros Beetles, female (left) and male. This sort of dimorphism is common when males compete for access to females. Tucson, Arizona, USA.

strategusscarabscarabaeidaeox beetlesrhinocerusrhinocerus beetlessexual dimorphism picturehornsbeetlebeetlesbugbugssexual selectionevolutionnatureentomologyinsectinsectsColeopteraPolyphaga

From Coleoptera: Beetles