The past week has brought in several calls about swarming beetles, which appear to be Carabid beetles of the genus Harpalus. Ground beetles are fast moving, predatory beetles that, as the name implies, forage on the ground. Outdoors they and their likewise predaceous larvae are found on the ground in all habitats, both grassy and forested areas.
Ground beetles have little interest in coming indoors, where there is little food. However they may accidentally enter homes when they slip under doors while trying to escape from daylight. Outdoors they hide under rocks, leaves, logs, etc. during the daylight hours.
Most ground beetles are relatively strong fliers and are readily attracted to lights when they embark on their nocturnal mating flights. Typically these flights occur once a year over a one or two week period.
The current flurry of calls about what one inquirer called those “crunchy black beetles” is likely the result of a recent mating swarm. The current ground beetle invasion will be short-lived, but other species of ground beetles, like the caterpillar hunter, may be evident at other times of year. None of these species pose any real harm to people or pets (some have large enough jaws to bite if you pick them up), and they do help feed the birds.
No control should be necessary for ground beetles. If you don’t like having all those crunchy beetles around, consider turning off the outdoor lighting around your home for part or all of the night. You should only need do this for a few days. For more information about ground beetles, the University of Kentucky has published a nice summary.