The western conifer seed bug, Leptoglossus occidentalis, an insect that seeks shelter indoors during the fall, has been migrating slowly eastward across the country. Though common in the western states, it was first noticed in Maine in 1994. Since then, this bug has spread throughout many areas of the state.

Typically, most homeowners who experience these household invaders have pine trees in the yard. This insect is similar in appearance to the squash bug and is about ¾” long. It has black, brown and white patterning on the back, a straw-like beak for a mouth and flared hind legs. In preparing for its buzzing flight, the bug lifts its wings to reveal a back that is orange with black blotches. When crushed or disturbed, it emits an offensive odor. These insects are harmless to people and possessions.

The western conifer seed bug feeds on the growing cones and seeds of pine and spruce during the spring and summer. In the fall, the insects start to accumulate on the outside of houses in clumps. As the day cools off, they make their way into the house. This behavior is similar to certain lady beetles, cluster flies, and boxelder bugs.

With the arrival of warmer weather in the spring, the insects migrate outdoors and the females lay eggs on needles of spruce and pine. The eggs hatch in about 10 days and the young, called nymphs, feed on the developing cones. Before reaching the adult stage in late summer, the nymph sheds its skin (molts) five times.

If you’ve had a problem in the past with these insects in the house, here are some tips to think about. Accumulations of the insects on the outside of the house can be swept away. Seal or caulk cracks and crevices leading into the house to prevent entry. Door and window screens need to be in place and intact. Soffit, wall, and attic vents should be screened as well. Consider screening the chimney and fireplace. Insects inside the house can be vacuumed or swept up and disposed. We do not recommend spraying for this insect.