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Western Conifer Seed Bugs

The large, brown bug, currently entering homes and causing concern among Massachusetts residents is the Western Conifer Seed Bug (WCSB), Leptoglossus occidentalis. This species, first described in California in 1910, has quickly moved eastward. In 1956 the WCSB was reported in Iowa and in1990 several were found in New York State.

Illustration by Gale E. Ridge, Connecticut Agricultural Experiment Station

Description:
The WCSB is a true bug, (order Heteroptera) in the family Coreidae. They are known as leaf-footed bugs because of a flattened segment resembling a leaf on their hind legs. This dull brown bug is 3/4 inch in length and has long hind legs. They are good, but noisy flyers and closely resembling the sound of a bumblebee. As a defensive mechanism when alarmed or handled, the WCSB omits a pungent odor from glands between the second and third pair of legs.

Life Cycle:
In the fall, the Western Conifer Seed Bug enters homes through cracks and crevices searching for protection from cold temperatures. In the spring they return to the outdoors to feed on the developing seeds and flowers of coniferous trees, including: white pine, red pine, hemlock, and spruce. The female lays rows of eggs on the needles and the eggs hatch in about ten days. The nymphs, which feed on the scales of the cones and occasionally the needles, pass through five stages of development and reach adulthood by late August. It is around this time that WCSBs begin their search for over-wintering sites.

Damage:
Even though they are harmless to people and do not sting, bite, or eat wood, the Western Conifer Seed Bug causes concern among the occupants of the homes they invade. At this time, it does not appear that the WCSB is destructive to conifer trees found in Massachusetts.

Control:
Prevent the entry of these bugs in buildings 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 vacumed into a bag and disposed of. We do not recommend the use of pesticides.

For more information:
View the The Connecticut Agricultural Experiment Station website fact-sheet: Western Conifer Seed Bug, Leptoglossus occidentalis Heidemann by Gale E. Ridge, Department of Entomology.

By Linda Cocca, October 2003

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