Mandibles and labium of D. hercules; engaged regions of mandibles were exposed using a file. A Interior view of the male head from the dorsal side; arrows indicate projections from the labium into the mouth cavity B lateral view of labium from the left side; arrows indicate projections into the mouth cavity.

  Part of: Ichiishi W, Shimada S, Motobayashi T, Abe H (2019) Completely engaged three-dimensional mandibular gear-like structures in the adult horned beetles: reconsideration of bark-carving behaviors (Coleoptera, Scarabaeidae, Dynastinae). ZooKeys 813: 89-110.