Antlers of the Insect World

What am I looking at?

This image shows two male stag beetles (members of the Lucanidae family) competing for a mate. These particular beetles were photographed in West Papua, a province in Indonesia, but the species can be found all over Southeast Asia. This species has mandibles (1) that can be longer than the rest of its body (2), plus long legs equipped with large, strong tarsal claws (3) for gripping tree bark. Click on the right arrow to see how a stag beetle uses its mandibles to grasp another male and toss it off a tree branch.

Biology in the background

Stag beetles are an excellent example of the concept of sexual dimorphism. This means that the appearance and anatomy of the males and females of the species are very different. This often occurs in so-called tournament species – those in which one sex competes for access to mates. In this case, the male beetles have developed oversized mandibles that resemble the horns of a stag – hence their name. The heads and mandibles of the females are much smaller and less prominent.

The males use their mandibles to grasp and toss other males off tree branches. Body and mandible size are indicators of a male’s so-called resource holding potential – a biological term describing an animal’s ability to win a fight. Having more access to resources means having more offspring and hence passing along more copies of one’s genes to the next generation. Through that process of sexual selection, stag beetle males have developed disproportionately large mandibles.

While most male stag beetles are around 5 centimeters long, they can grow up to 12 centimeters long, or about the size of a human palm.

Technique

These images were created using macrophotography.