Western Conifer Seed Bugs

Western Conifer Seed Bug © Dawn Dailey O'Brien, Cornell University, bugwood.org
Western Conifer Seed Bug © Dawn Dailey O'Brien, Cornell University, bugwood.org

Residents of Massachusetts may see this large, brown home invader come fall. First described in California in 1910, Western Conifer Seed Bug (Leptoglossus occidentalis) has quickly moved eastward. In 1956 the WCSB was reported in Iowa and in 1990 several were found in New York State. 


A true bug (order Heteroptera) in the family Coreidae, the dull-brown WCSB is known as leaf-footed bugs because of a flattened segment resembling a leaf on their hind legs. As a defensive mechanism when alarmed or handled, the WCSB omits a pungent odor from glands between the second and third pair of legs. They are sometimes considered a “stink bug” due to the pungent odor they emit when alarmed, handled, or smooshed.

Life Cycle

The female lays rows of eggs on the needles coniferous trees (hence the name), including white pine, red pine, hemlock, and spruce. Eggs hatch in about 10 days and the nymphs feed on the scales of the cones and occasionally the needles. They reach adulthood in late August. 

In the fall, the Western Conifer Seed Bug enters buildings through cracks and crevices searching for protection from cold temperatures. Find out what to do if you encounter one.

Situations & Solutions

Even though they are harmless to people and do not sting, bite, or eat wood, the western conifer seed bug (WCSB) may cause concern. They are good but noisy flyers, and can sound like a buzzing bumblebee.


Prevent the entry of these bugs by calking openings around windows, doors, and chimneys, repair damaged window screens, and screen attic and wall vents.

The bugs can be easily captured and returned to the outdoors or vacuumed into a bag and disposed of. There is no need to resort to insecticides. Chemicals are dangerous—western conifer seed bugs are not.