What's That Bug?

Are you finding little black bugs with red lines, about ½ inch long, inside your house or outside on the foundations on sunny walls? Do you have an invasion of these insects nearly every spring and again in fall? If so, chances are you have a female box elder tree in your yard or nearby. Box elder bugs, as they are called, feed on the seeds and foliage of female trees, and to a lesser extent, on ash and maple. In fall, the bugs move to protected sites where they can overwinter, such as inside or under you house. Box elder bugs you find in spring are those which survived the winter, perhaps in your house, and will soon die of “old age”. In fall, you can probably expect another invasion of the next generation of box elder bugs.

Adult box elder bugs are elongate, 1/2 inch long insects with sucking mouthparts. They are mostly black with some red markings. There are three narrow red lines on the segment behind the head, one down the center and one on either side and a thin red inverted "V" about the middle of the back. The wingless immature or nymphal stage has a black head, antennae, and legs. The red abdomen has an orange-yellow stripe and spot down the center of the back.

The good news, is that they cause little or no damage to the trees, so tree protection is not needed. You already know the bad news, that the bugs are a nuisance. However, they will not reproduce in the house, nor will they feed on plants or furnishings indoors. They will soon die of old age. Inside the house, you can vacuum them up periodically, and those that escape will soon die off. Reduce the numbers that will enter your house in fall by caulking cracks, mending screens, and attaching "sweep strips" to the bottom of doors. These efforts will keep other insects out as well.