The Carlisle Mosquito Online

Friday, January 25, 2002


Biodiversity Corner:
Western Conifer Seed Bug

Name: Western Conifer Seed Bug or Leptoglossus occidentalis or leaf-footed bug or
unwanted house guest.

Found: by Tom Brownrigg, December, 2001, in the house.

Distinguishing characteristics: Dark brown and about 3/4 inch long, these bugs belong to the family Coreidae and like many other members of the family, part of the hind leg is flattened into a leaf-like shape. Bugs with this characteristic are commonly called leaf-footed bugs. When they fly, you can see yellowish-orange areas on their backs. They have a faint white zigzag marking across the middle of the upper surface when the wings are at rest.

Food: Western Conifer Seed Bugs are true bugs with piercing, sucking mouthparts which they use to pierce the scales and then suck out the pulp of seeds of over 30 species of trees including pine, spruce, fir, arborvitae and hemlock.

Travel Diary: This bug was first documented in the USA in California in 1910. With a total disregard for its name it traveled eastward, rather slowly, turning up in Iowa in 1956. May have something to do with being leaf-footed. Anyway, it moved steadfastly on ­ to Wisconsin and Illinois in the 70s, Minnesota and Michigan in the 80s, upstate New York in January 1990, and Acton Street in Carlisle about 5 years ago.

Behavior: In late summer and early fall these bugs start looking for protected dry sites in which to spend the winter. Tom's house is in a prime habitat of fir, spruce and pine making it a choice destination and in the fall he has seen these bugs massing on the sunny side of the house ­ probably counting down the ten best ways to get inside. In the wild they settle into tree crevices, under bark, and in bird and rodent nests where they remain torpid until spring. (I have a friend like that.)

Best Behavior: They don't bite or sting and they refrain from feeding on or causing damage to fabrics, woods or other articles within the home. They simply use our homes, as we do, for shelter from the cold weather. (As a precaution, consider hiding the pine nuts.)

Worst Behavior: These bugs are becoming a problem in conifer seed orchards since they eat the crop. Entomologists are trying to quantify the impact of the bug on the vast acreages of lodgepole pine forest in the western US and Canada which require millions of seedlings per year to sustain the annual timber harvest. Also, there is an estimate of 41% loss of seed crop in Douglas-fir in areas of heavy feeding. In the east, the bad behavior is more personal; these leaf-footed seed suckers can give off a nasty odor if you handle them. (I have a dog like that.)

Summary: All things considered, I'd rather be a leaf-footed seed sucker than a yellow-bellied sapsucker. Don't even mention the goatsucker.

References: Carolyn Klass, Department of Entomology, Cornell University Cooperative Extension and Gale Ridge-O'Connor, Connecticut Agricultural Experiment Station At either site, use the search option and enter 'western conifer'.

Submissions for the Biodiversity Corner are invited from all interested observers of nature - there is no requirement to be an entomologist - you might be an etymologist. Just follow the format of today's column (or not) and send a drawing or photo (or not) to Kay Fairweather at 392 School Street, Carlisle MA 01742 or to

2002 The Carlisle Mosquito