Description of ground beetles
Ground beetles are very common "outdoor" insects that occasionally become pests by wandering into houses and buildings by mistake. They do not damage household structures or furniture and are harmless to people and pets. They are actually beneficial because they feed on insect larvae. However, large numbers are occasionally present and they become more annoying than beneficial. There are hundreds of species of ground beetles commonly found in Iowa.
Ground beetles live on the ground under leaves, logs, stones and other debris. They feed mostly at night, and may be attracted to lights. They usually gain entrance to the house by crawling in through small cracks or openings, or through open doorways and windows.
Management of ground beetles
Controlling ground beetles is usually not necessary. However, if invasion is persistent or especially troublesome you can eliminate or treat their outdoor hiding places as practical. Spot treatment of likely sources with the insecticide sprays mentioned below is possible. Invasion of ground beetles can be reduced by eliminating entry points by caulking gaps and cracks in the foundation and siding, or repairing windows and screens. In severe cases, it may be desirable to apply a residual insecticide in a 10-foot band around the house, to the house foundation, doorways and other points of entry. Additional residual insecticides are available to pest control operators if you choose to have this treatment professionally applied. The only effective control for ground beetles already inside is to pick them up and discard. For more information on insecticides please see this article.