Carabid invasion

These inch-long beetles in the genus Harpalus are the latest insect
Texas plague to hit homes, businesses and schools.

The insect of the week, at least in east Texas, is a carabid beetle in the genus Harpalus. 

Ground beetles are fast-moving, predators 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 or businesses when they slip under doors in their escape from daylight. Outdoors they hide under rocks, leaves, logs, etc. during the daylight hours.

Most ground beetles are relatively strong fliers and will be readily attracted to lights during 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 chemical control should be necessary for ground beetles. Beetles that are drawn into lights are either (1) going to be eaten by birds or other predators, or (2) going to fly away the next evening.  The best advice you can give customers who don’t like having all those crunchy beetles around, is to consider turning off the outdoor lighting around the account for part or all of the night. This should be necessary for only a week or so, until the flights subside.

If a customer insists on some control action, be aware of the recent label changes for pyrethroid insecticides. New pyrethroid labels do not allow application to concrete surfaces that will be exposed to rain. This would include sidewalks around buildings, and sides of buildings over concrete that not protected by eaves or canopies from the rain. Granular baits designed for crickets or cockroaches will not be effective against these predatory beetles.  For more information about ground beetles, the University of Kentucky has published a nice summary.