Habits and Traits of Darkling Beetles

Darkling beetle
Darkling beetle. Getty Images/up close with nature

The family Tenebrionidae, the darkling beetles, is one of the largest beetle families. The family name comes from the Latin tenebrio, meaning one who loves darkness. People raise darkling beetle larvae, known as mealworms, as food for birds, reptiles, and other animals.

Description

Most darkling beetles look similar to ground beetles — black or brown and smooth. They're often found hiding under rocks or leaf litter and will come to light traps.

Darkling beetles are primarily scavengers. The larvae are sometimes called false wireworms because they look like click beetle larvae (which are known as wireworms).

Though the Tenebrionidae family is quite large, numbering close to 15,000 species, all darkling beetles share certain characteristics. They have 5 visible abdominal sternites, the first of which is not divided by coxae (as in the ground beetles). The antennae usually have 11 segments and may be filiform or moniliform. Their eyes are notched. The tarsal formula is 5-5-4.

Classification

Kingdom – Animalia
Phylum – Arthropoda
Class – Insecta
Order – Coleoptera
Family – Tenebrionidae

Diet

Most darkling beetles (adults and larvae) scavenge on plant matter of some kind, including stored grains and flour. Some species feed on fungi, dead insects, or even dung.

Life Cycle

Like all beetles, darkling beetles undergo complete metamorphosis with four stages of development: egg, larva, pupa, and adult.

Female darkling beetles deposit their eggs in the soil. Larvae are worm-like, with slender, elongate bodies. Pupation usually occurs in the soil.

Special Adaptations and Defenses

When disturbed, many darkling beetles will emit a foul-smelling liquid to dissuade predators from dining on them. Members of the genus Eleodes engage in a somewhat bizarre defensive behavior when threatened.

Eleodes beetles raise their abdomens high in the air, so they almost appear to be standing on their heads, while fleeing the suspected danger.

Range and Distribution

Darkling beetles live worldwide, in both temperate and tropical habitats. The family Tenebrionidae is one of the largest in the beetle order, with well over 15,000 species known. In North America, darkling beetles are most diverse and abundant in the west. Scientists have described 1,300 western species, but only around 225 eastern Tenebrionids.

Sources:

Family Tenebrionidae - Darkling Beetles - BugGuide.Net

Darkling Beetle, St. Louis Zoo

Darkling Beetle Fact Sheet, Woodland Park Zoo

Borror and Delong's Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson