Stag Beetles

About 24 species in North America north of Mexico
Family

Lucanidae (stag beetles) in the order Coleoptera (beetles)

Description

While stag beetles are not very colorful, they make up for it in pincers! Male stag beetles usually have enlarged, sometimes astonishing jaws. Most are black, brownish, or reddish brown. They are strong, elongated beetles. The antennae are enlarged at the tip or clubbed, with segments that fan open like leaves but that cannot be pressed together tightly into a ball. The antennae have 10 segments, and on many species the antennae are elbowed.

The jaws of male stag beetles are enlarged, imposing pincers that are used for fighting over females. On some species, they look like antlers (hence the name “stag beetle”). The pincers of females, though less spectacular, are still well-developed.

The larvae of stag beetles are whitish, C-shaped grubs that live in rotting wood. The heads are often brownish or black, and they have three pairs of legs. They look a lot like the larvae of scarabs and other beetles.

Size

Length: from less than ½ inch to nearly 2½ inches (adults; varies with species).

giant_stag_beetle_10-09-13.jpg

Photo of a male giant stag beetle on moss
Giant Stag Beetle (Elephant Stag Beetle) (Male)
Habitat and conservation

Most stag beetles are found on the ground in forests. Others frequent sandy stream banks near driftwood. As with other insects, although they can go almost anywhere by foot or by wing, they tend to be near their food sources and egg-laying places. The larvae live in rotting logs, and the adults consume tree sap. In some places, stag beetle larvae have been found in deep layers of hardwood mulch used in hiking trails and playgrounds. Stag beetles are sometimes attracted to lights at night.

Foods

Larvae eat rotting wood and the juices associated with it. Adults eat tree sap where it runs after a branch or the bark has been injured. They may also eat rotting fruit, and some species apparently eat the sweet “honeydew” secretions of aphids.

image of Stag Beetles Distribution Map
Distribution in Missouri

Statewide.

Life cycle

Those jaws don’t just look like antlers; male stag beetles combat each other for mating opportunities just as male elk and deer do. The best mating sites are where females go to eat, or near the rotting wood where females lay eggs. Using their huge jaws, males grapple with each other for the best locations. After hatching from eggs, the larvae live in rotting wood, growing and molting, often for years. When fully grown, the larvae pupate surrounded by wood chips, then emerge as adults.

Human connections

“Will it pinch me?” Maybe, if you handle it—but the jaws of males are used primarily for fighting other males, and they don’t bite people aggressively. Just about any creature with a jaw can potentially bite, and will, in defense. The larvae, meanwhile, are important decomposers of dead wood.

Ecosystem connections

Several animals, including raccoons and woodpeckers, probe or poke through rotting logs and eat the grubs. Many other animals, including birds, bats, and skunks, frogs, eat the adults. Several types of flies and wasps parasitize the larvae, laying eggs on them that hatch and devour the host.