Ground beetles are insects that belong to the family Carabidae. They rank among the largest, diverse and, most common families of beetles in North America, with more than 2,600 different species found across the continent. Over 800 species of ground beetles occur in Canada alone. They are commonly found in the soil living on ground surface where they prey on a variety of invertebrate pests. Certain species also help control the spread of weeds by feeding on the seeds that spawn the pesky plants. Despite being beneficial to the environment, ground beetles can sometimes be pests that overrun buildings in large numbers or eat the seeds of important crops, such as corn.
Appearance / Identification
Ground beetles vary in size and shape but most are oval and elongated. They range in size from about 2 to 25 mm or more in length. Most species are black or otherwise dark in colour, though certain types of ground beetles feature an iridescent quality characterized by metallic hues of blue, green, orange, red, yellow, copper, or a combination thereof. Like other insects, the body is divided into three body parts: head, thorax, and abdomen. They have three pairs of legs and two pairs of wings, with the outer wings hardened into elytra used as protective covers. Because most are predators, they have prominent mandibles for capturing and devouring their prey. In fact, ground beetles can be identified and distinguished from similar-looking species by their ability to run quickly and their tendency to scurry for cover when disturbed.
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Ground beetles live and breed in the soil. True to their name, the insects are regularly found on the ground under logs, rocks, wood, leaves, boards, and other debris. Ground beetles commonly reside in agricultural zones, such as fruit orchards, and rank as the most frequently encountered type of beetle in the yards and gardens of many Canadian provinces. When the pests move indoors, they can often be found hiding in damp basement areas or under objects on the floor. Most ground beetles are nocturnal creatures that remain hidden during the day. Although they invade buildings from time to time, ground beetles only reproduce outdoors.
Widely regarded as beneficial insects due to their eating habits, ground beetles are predators which feed on common invertebrate pests such as ants, aphids, caterpillars, maggots, slugs, and worms. Some species, such as the caterpillar hunter, focus on a particular food source exclusively, while others are generalist feeders. Certain ground beetle species even demonstrate phytophagous tendencies by preying on the seeds, shoots, and pollen of plants rather than feeding on other animals. Some ground beetles can eat as much as four times their own body weight in prey on a daily basis.
Life Cycle / Reproduction
Ground beetles develop and mature by undergoing complete metamorphosis from egg to adult. Females typically produce one generation of offspring each year and lay their eggs individually in the soil. A single litter of ground beetles contains 30 to 600 offspring that hatch from the eggs as larvae and usually complete three larval instars before pupating. Ground beetles emerge as adults shortly after completing the pupal stage of the life cycle, which occurs in the soil and is rarely witnessed. Full development from egg to adulthood can take place within a single season. Adult ground beetles typically live for one to four years and are usually most active between the months of April and October.
Problems Caused by Ground Beetles
As beneficial insects that play an important role in curbing populations of pests and weeds, ground beetles generally only become a problem when they occur in large numbers and move indoors. A typical ground beetle infestation comprises just a handful of the harmless insects. In some cases, however, ground beetles will enter buildings in large numbers and cause panic or alarm, even though the pests do not pose a health threat to people or damage property. Certain species are capable of releasing odorous secretions, while other types of ground beetles can be major crop pests that feed on seeds of corn.
Detection / Signs of Infestation
Ground beetles are occasional invaders, they are typically encountered from spring to fall and enter homes most frequently during the middle or end of summer. Attracted to light, ground beetles are noticeable when they congregate around well-lit structures, before entering all at once and creating an infestation. Since ground beetles do not breed indoors, they leave behind few other signs of an infestation.
Ground beetles often gain access to buildings through cracks, crevices, and other small openings, repairing and sealing these potential entry points will help keep the pests from invading. Other ways to prevent a ground beetle infestation include keeping mulch away from the building foundation and either reducing the level of outdoor lighting within the immediate vicinity of the structure or using yellow light bulbs instead of bright white ones. Furthermore, the yard should remain free of rocks, stones, wood, boards, leaves, and other debris under which ground beetles typically like to live.
Control / Removal
Smaller infestations of ground beetles can often be vacuumed up or captured in a container and removed. Sticky traps may also help control and manage the pests. Large infestations, on the other hand, may require the application of an appropriately labelled insecticide around the perimeter of the home. Insecticides must be handled carefully and applied in accordance to label directions for safety and in order to work effectively. A knowledgeable pest control professional can be consulted to manage an infestation while providing additional information on how to prevent ground beetles from invading in the future.
Pictures of ground beetles.