Tiny rove beetles are everywhere, yet most people rarely notice these beneficial insects. Rove beetles, which belong to the family Staphylinidae, inhabit a variety of interesting ecological niches, including ant nests, fungi, decaying plant matter, dung, and carrion.
Most rove beetles make their living after sunset, when they emerge from hiding to pursue insect prey. You’ll find rove beetles by looking in moist environments crawling with maggots, mites, or other even springtails. Some rove beetles react to perceived threats by tipping their abdomens up, like scorpions do, but this gesture is all bark and no bite. Rove beetles can’t sting, but the larger ones can inflict a nasty bite if mishandled.
Adult rove beetles rarely top 25 mm in length, and most measure considerably less (under 7 mm or so long). Their elytra are noticeably shortened, though they can fly quite well thanks to functional hindwings tucked carefully underneath. In most rove beetles, you can see several exposed abdominal segments because of this diminished wing structure. Rove beetles have mouthparts modified for chewing, often with long, sharp mandibles that close sideways across the front of the head. Because many species sport a pair of short projections at the end of the abdomen, people often mistake them for earwigs.
Rove beetle larvae have elongated bodies, and appear slightly flattened when viewed from the side. They’re usually off-white or beige in color, with a darker head. Like the adults, the larvae often have a pair of projections alongside the tip of the abdomen.
The large family Staphylinidae includes many rove beetle genera with eating habits as diverse as the group. Most rove beetles are predatory as adults and larvae, feeding on other, smaller arthropods. Within the family, however, you’ll find rove beetles that specialize on a diet of fungal spores, others that eat pollen, and still others that feed on the regurgitated food from ants.
As all beetles do, rove beetles undergo complete metamorphosis. The mated female deposits a cluster of eggs near a source of food for her offspring. Rove beetle larvae typically inhabit moist environments, such as in soil covered by decaying leaf litter. The larvae feed and molt until they are ready to pupate. Pupation occurs in moist leaf litter or in the soil. When the adults emerge, they are very active, especially at night.
Special Adaptations and Defenses:
Some rove beetles use chemicals in clever ways to their own advantage. Those in the genus Stenus, for example, live around ponds and streams, where they can find their favorite prey, springtails. Should a Stenus rove beetle suffer the unfortunate mishap of slipping into the water, it will release a chemical from its hind end which magically lowers the surface tension behind it, effectively thrusting it forward. Paederus beetles defend themselves by emitting the toxic pederin chemical when threatened. More than one entomology student has borne the blisters and burns from handling Paederus rove beetles. And at least one male rove beetle, Aleochara curtula, applies an anti-aphrodisiac pheromone to his female partner, rendering her undesirable to any future suitors.
Range and Distribution:
Rove beetles inhabit moist environments throughout the world. Though the family Staphylinidae numbers well over 40,000 species worldwide, we still know relatively little about rove beetles. The classification of rove beetles and related groups is ever changing, and some entomologists estimate that Staphylinids may eventually number well over 100,000.
- Borror and DeLong’s Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson
- Insects: Their Natural History and Diversity, by Stephen A. Marshall
- Kaufman Field Guide to Insects of North America, by Eric R. Eaton and Kenn Kaufman
- Rove Beetles, by Carol A. Sutherland, Extension and State Entomologist, New Mexico State University, accessed November 28, 2011