Stag Beetle

Quick Take

• Those giant mandibles look deadly, but they have absolutely nothing to do with eating or defense. See the wrestling mandibles →
• Stag beetle larvae are actually larger than the adults, and the reason why is stranger than you'd expect. Explore larval size details →
• This insect's fossil record stretches back further than most people would guess, and the preservation method makes it even more remarkable. Discover the fossil record →
• Adult stag beetles barely eat, yet somehow they survive. The way they pull it off is surprisingly clever. See how adults survive →

The stag beetle belongs to a family of large, hard-shelled, flying insects whose distinguishing trait is the ability to consume rotting wood as a larva. The name of this insect is derived from the giant mandibles on the male, which resemble the antlers of a deer (a “stag”) in the way they curve and branch. Their numbers appear to be declining in some parts of their range due to the loss of habitats and food sources.

3 Incredible Stag Beetle Facts

• The giant mandibles for which this species is known have nothing to do with feeding. Instead, they allow the males to wrestle each other for access to females. The larger and stronger male usually emerges as the victor from the contest.
• After copulating with her partner, the female will often return to the place of her birth and lay around 30 eggs near rotting wood in the soil. The larvae emerge shortly afterward and spend a few years in grub form, feeding on the rotting wood. They undergo a few different larval stages before becoming adults. The total lifespan from the larval stage through adulthood can sometimes reach up to seven years.
• The oldest known fossil of this insect dates back to the Middle Jurassic Period, approximately 150 to 160 million years ago. The form they were found in is known as a compression fossil, literally imprinted into sedimentary rock. Better-preserved fossils, dating back around 20 to 30 million years, from the modern-day Dominican Republic, were later found encased in amber.

Species, Types, and Scientific Name

The scientific name for the stag beetle family is Lucanidae. This name comes from the ancient Italian region of Lucania, at the southern end of the peninsula, where these beetles were used to make amulets. There are some 1,200 documented stag beetle species around the world. The best-known species is perhaps the European stag beetle, found all across the continent. Other well-known species include the multi-colored rainbow stag beetle of Australia and the cottonwood stag beetle of Arizona and the southwestern United States.

Appearance: How to Identify Stag Beetles

An adult is characterized by a wide, segmented body and two pairs of wings. It is usually colored black or brown, but a select few species exhibit all manner of bright colors such as metallic green and iridescent red. The rainbow stag beetle has an entire range of bright rainbow colors. Adults normally grow 1 or 2 inches in length, but the largest species in the world, the giraffe stag beetle of Asia, measures up to about 4.7 inches long, much of which consists of the massive mandibles. Males are noticeably larger than females, primarily because of their mandibles. The larvae, by contrast, have a more grub-like appearance with an orange head. Measuring up to around 4.3 inches long, they’re generally larger than the adults, even without the giant mandibles.

While stag beetles have large mandibles, they generally do not bite humans. If they do feel threatened and bite, however, male stag beetle bites aren’t harmful, while female bites can be quite painful.

Habitat: Where to Find Stag Beetles

These insects are found all over the world, usually in places with loose soil and high average temperatures. While they tend to be found in wooded lands, they also occupy many unexpected habitats. The cottonwood stag beetle of Arizona is even known to consume the wood chips of playgrounds.

Diet: What Do Stag Beetles Eat?

The stag beetle is an herbivorous insect. Its digestive system is specifically adapted for consuming wood as food. The technical term for an animal that depends mostly on wood in its diet is a xylophage.

What eats the stag beetle?

This species is preyed on by a wide range of birds, amphibians, lizards, small mammals, and insects. Crows, foxes, and kestrels are particularly common predators, especially when the beetle is most vulnerable in the mating season.

What does the stag beetle eat?

This insect spends the first several years of its life as a larva, feeding on rotten wood. The adult largely relies on the fat reserves left over from the larval stage to survive for the rest of its lifespan. When it does eat at all, the adult will consume rotting fruit or sap with its soft tongue.

Prevention: How to Get Rid of Stag Beetles

This species does not generally cause any harm to humans, because (unlike termites and other pests) they tend to live underground and feed only on rotting wood, rather than on structural timber. Nevertheless, if you don’t want stag beetles lurking around your home, then the best way to get rid of them is to remove any remnants of rotting wood from your property. They are most likely to be found around rotting fences. Chemical use is generally not recommended, because it might cause more problems than it solves. Since population numbers have declined in many parts of their range (particularly Europe), it’s a good idea to just leave them alone unless it’s absolutely necessary to remove them. Some people even deliberately attract stag beetles by placing decaying wood on their property.