Ground beetles in homes
Ground beetles are one of the most common groups of beetles in North America. They are found in many types of environments including forests, fields, shorelines, agriculture. They are also found in landscapes and around homes and occasionally become a nuisance inside buildings.
Most ground beetles are small to moderate sized insects, about 1/8 - 1/2 inches long (a few can become as large as 1 inch in length). They are generally flattened insects with prominent mandibles (jaws). Most are black or brown and iridescent, although some species can be brightly colored, including blues, greens, and reds. The head is narrower than the neck (called the pronotum) and has moderate length, thread-like antennae. Ground beetles have long, slender legs. (Figs. 1, 2, 3, 4)
Ground beetles are active at night and are occasionally attracted to lights. They hide during the day and are typically found on the ground under leaves, logs, stones, loose bark, and in grassy areas. When exposed, ground beetles typically move quickly to find shelter but rarely fly. Nearly all ground beetles are predaceous, feeding on other insects as well as other invertebrate animals, and are considered to be beneficial.
You can find ground beetles during spring and summer and into the fall. Ground beetles are most common entering homes in mid and late summer. They find their way into buildings through cracks, spaces and other small openings. Once inside, they are sometimes found in hidden, damp areas in the basement or under boxes or other objects on the floor.
Ground beetles are not harmful to people (It is possible that if they are mishandled, they could pinch the skin) nor are they are injurious to buildings, food, or clothing. They are just a nuisance when they are found indoors. In most cases, only a few ground beetles are found in buildings at any given time, although there are times when large numbers will enter structures. Ground beetles are relatively short lived indoors and do not reproduce there.
In most cases, you will only encounter just a small number of ground beetles indoors. The only necessary control is physical removal, e.g. capture them in a container or remove them with a vacuum. You could also try setting out sticky traps, such as those used for cockroaches. Place these traps in areas where ground beetles are most commonly found, especially along walls.
If you encounter a large number of ground beetles, you can reduce their numbers through a number of non-chemical steps:
- Seal and repair potential entry points, such as cracks in the foundation, gaps and spaces around doors, ground level windows and similar areas.
- Thin out or remove wood mulch or other organic mulch that is directly adjacent to the foundation.
- Stack firewood away from the home as far as is practical.
- Remove stones, leaves, boards, and other nearby debris.
- Cut or remove tall grass and weeds around the home.
- Minimize the use of lighting immediately next to the structure or switch the lights from bright white to yellow to minimize attracting ground beetles.
Insecticides are not necessary if only a few ground beetles are found indoors. In cases when large numbers are getting inside buildings, an insecticide treatment around the exterior of homes is an option. An insecticide applied around the foundation helps to reduce the number of ground beetles that may enter buildings. Common examples include products that have active ingredients like, bifenthrin, cyfluthrin, deltamethrin, and permethrin purchased as a liquid read-to-use or occasionally as a granular ready-to-use.
Caution: Read all label directions carefully before buying insecticides and again before applying them. Be sure the product you wish to use is labeled for use around the foundations of buildings. Information on the label is the final authority on how to use a pesticide.