National Museum of Natural Science

The awe-inspiring mandibles provide many benefits for male stag beetles. But, they also come at a considerable cost. The different shapes and forms of mandibles inspire people to collect these beetles, leading to their demise. Large mandibles also restrict movement by adding weight and shifting the center of gravity forward and upward. The increased length due to the mandibles makes it difficult for these beetles to hide. Other parts of the male anatomy have to undergo changes to adjust posture and to decrease the burden of the mandibles when moving.

Image is of male Darwin's beetle (Chiasognathus granti Stephens). 

Image source: Flickr image-sharing database. Photographer: María Jesús.

The cost of mandibles