Hosts or Prey
Caterpillars, root-feeding insects, soil-dwelling insects, and other ground-dwelling invertebrates including millipedes, slugs, and snails
Identification
Predaceous ground beetle (carabid) adults are elongate with a hard, shiny, upper surface. They have prominent, long legs and antennae. Most species are medium to large, about 1/8 to 1 inches (4–25 mm) long. Their color varies greatly, but many species are blackish or dark reddish. Some carabids are brilliantly colored or iridescent, such as the endangered delta green ground beetle, Elaphrus viridis.
The length, shape, and width of the head and thorax relative to the width of the abdomen varies greatly among species; for example Scaphinotus species (called snail eaters) have an unusually long, narrow head that can reach into the opening of the shell of snails on which they feed. Most species have a prominent thorax that is narrower than their abdomen. Their long antennae have 11 segments and are not clubbed at the end.
Eggs are oblong and laid in moist soil. Larvae dwell in organic litter on the ground or in topsoil. Larvae are elongate and have a relatively large head with distinct, curved, chewing mouthparts.
Pupae are brown to yellowish. In most species pupae occur in a cocoon underground, in a soil cell formed by the last instar.
Lookalikes
Carabid adults resemble those of plant-feeding darkling beetles (Tenebrionidae). Carabids have enlarged basal segments (coxae and trochanters) at the base of their rear pair of legs; trochanters on their underside partly cover several abdominal segments. Darkling beetles lack enlarged basal segments on the legs. Darkling beetles' antennae are attached beneath a distinct ridge on each side of their head; carabids lack this ridge.
Life Cycle
Carabids develop through 4 life stages: egg, larva, pupa, and adult. Adult females lay eggs individually in soil, commonly about 100 or more eggs during her lifetime. After hatching, larvae develop through 4, increasingly larger instars. Most species pupate in a cell they form in soil, commonly several inches beneath the surface.
Carabids can live for 2 or more years, and take several months to more than 1 year to complete their development from egg to adult, varying by diet, location, and species. Many species complete their life cycle from egg to adult in about 1 year.
Habitat
Carabids occur in most terrestrial habitats. They are common in crops, gardens, landscapes, and wildlands. Adults are mostly night-active, ground-dwellers. However, adults of many species will climb plants during the night to feed on caterpillars and immatures of other insects.
Adults are fast runners and rarely fly; many species have the forewings fused and are flightless. Adults during the day and larvae at all times can be found in compost piles, leaf litter, mulch and under objects on the soil and rocks, especially in moist locations. At night adults seek prey on the surface of plants or soil.
Species
Over 2,500 species are known in North America. There are at least 800 species of predaceous ground beetles in California.
More Information
- California Insects, UC Press
- Coleoptera (Beetles) of Orange County, California (and Nearby Places), UC Irvine
- Immature Stages of Carabidae, UC Riverside
- Natural Enemies Handbook, UC Integrated Pest Management Program
- Protecting Natural Enemies and Pollinators, UC Integrated Pest Management Program
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Coleoptera
- Family: Carabidae
