ORIGINS: Native to Japan and China; brought to U.S. in 1900s to control certain pests. First noticeable U.S. outbreak occurred 20 years ago in Louisiana.
PREVALENCE: They’re more obvious now because they congregate in small groups over the winter. Most seek shelter in walls of buildings or elsewhere, but some find their way indoors.
NESTING: As insects, they can’t generate their own heat, so they winter in warm, dry cavities. They snooze on cold days and wake up and move around on warm ones. This will happen throughout the winter, resulting in days when they are out and days when you don’t see them.
CONTROL: Insecticides tend to be ineffective. Seal cracks and openings around your home. Vacuum up individual bugs — don’t squash them. They are attracted to light, so a light trap for flying insects might help.
HARMFUL? They do not eat building materials, they simply enter through existing openings. Their bite is not toxic, although some people may develop an allergic reaction.
BENEFITS: They devour pests such as aphids, which reduces use of insecticides on some crops and reduces crop losses.
BYE-BYE: They will leave your house in the spring.
Sources: USDA; University of Nebraska-Lincoln; Michigan State University
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