Common black ground beetles are attracted to light, and for this reason they may accidentally make their way into the house since they are active at night. While this may seem like an annoyance at the time, common black ground beetles are actually quite beneficial to the home and garden.
Common black ground beetles (Pterostichus melanarius), also known as carabids, grow to lengths of 1.2 to 1.5 cm (1/2 to 5/8 inch). The body is flattened and long, the head is narrow with large eyes, a strong curved lower jaw and very tiny antennae. The hard-shell wing coverings have lengthwise grooves and meet in the centre of the back. They do not fly so they have long legs that enable them to run fast. Black beetles are glossy black in colour except for a small amount of reddish brown on the legs and antennae.
Breeding begins in late summer and then the female lays eggs just below the surface of the soil. After the larvae hatch, they live all winter in the ground and begin to feed in early spring as they turn into pupae. In the summer they will have grown into adults and emerged from the soil. It takes an entire year from the time the eggs are laid for a beetle to reach maturity. Many adult beetles can live to the age of 2 or 3 years old or older.
Beetles are sometimes considered a nuisance especially when one makes it into the house, but don't step on that bug just yet, as common black ground beetles are actually beneficial. These hard-shell insects feed on many harmful household and garden pests including cutworms, fly maggots, caterpillars, aphids, weevils, other beetles, slugs and snails. So if a beetle makes it into the house, picking it up and placing it back outside is ultimately better for the home and garden.
To control and prevent common black ground beetles, moving or getting rid of their hiding places is the first step to take. Beetles like to hide under rotten boards, in piles of leaves or rocks and in and around decayed logs or firewood. To keep beetles from entering the home, caulking or screening the areas of beetle entry will help. Spraying insecticides around the windows, doors and in the yard area can also aid in controlling beetles, but it is best to avoid the use of chemicals if at all possible.