Male (top) and female western hercules beetles (Dynastes granti) on their host plant, an ash tree.
Rhinoceros Beetles, female (left) and male. This sort of dimorphism is common when males compete for access to females. Tucson, Arizona, USA.
Onthophagus gazella - Gazelle Scarab. Arizona, USA.
Strategus Rhinocerus Beetle. Tucson, Arizona, USA.
Male (right) and female ox beetles (Strategus sp.), showing the strong dimorphism between the sexes. Males use their impressive horns to fight each other over access to females.