Stink ‘friends’ (not stink bugs)

western conifer seed bug
A western conifer seed bug (Leptoglossis occidentalis).

One of the early signs of fall in our household is the first appearance of a western conifer seed bug on a windowsill inside. In years when the population of this insect is booming (especially inside our houses, it seems) our WSU Master Gardener clinics and our Extension office phones are ringing with questions about them—usually from people new to forest living.

Their frantic buzz as they fly around lights and the flash of yellow and black are a bit heart-stopping. But these bugs have no stingers, do not spoil our foodstuffs nor destroy our dwellings. They just like to share our winter quarters… When they land you can see the flattened band on the hindmost legs that puts them in the leaf-footed bug family.

Many people call them stink bugs (for reasons easily discovered when handling them) but entomologists reserve that name for a different family. The Latin name for the western conifer seed bug is Leptoglossus occidentalis, meaning “western narrow-tongue”. That tongue is used to suck the juices out of the seeds growing in cones of as many as 30 species of trees. They are considered a pest in seed orchards where selected trees are maintained for their annual cone crop.

Conifer seed bugs mate and lay their small barrel-shaped eggs on foliage in mid- to late spring. They hatch after about 2-1/2 weeks of development and feed on maturing cones in treetops throughout the summer, becoming adults in late August. As temperatures drop during the fall and early winter, the adults look for a dry over-wintering location where they go into a state of torpor until spring. Favorite spots are under peeled bark and in bird and rodent nests.

Obviously, some of these bugs have higher ambitions for winter lodgings than rodent nests, and choose our houses instead. In the fall when they sometimes aggregate on the south-facing walls of houses in large numbers, you may be able to simply hose them off with water or attack them with a shop vac. No insecticide is registered for inside use on them. Most advice runs along the lines of preventing entry by sealing cracks around windows and doors. But I’m here to tell you that after 25 years of sustained efforts with a caulking gun, I still can sometimes find a dozen bugs flying around inside on a sunny winter day.

My husband once suggested that it might be easier to change my attitude toward the bugs than to successfully fortify our house. Joining in this spin campaign, our kids renamed them “stink friends”. I once found a toy airplane where several bugs had even been enlisted as passengers. Nowadays, they’d have been stopped for carrying concealed chemical weapons.

The chemical the conifer seed bugs release is hexanal, and it functions as an alarm pheromone to communicate the presence of a threat and to repel predators. However there are several heroes of our winter woods who eat these bugs with gusto, including flickers, gray and Steller’s jays, chestnut-backed chickadees and hairy woodpeckers. We evict our bugs into the snow bank outside our window where they are immobilized by the cold and provide us entertainment as the birds discover them. Free birdfeed—now there is a positive spin. For mass collecting from those sunny windows, hold a square-sided plastic container firmly to the glass below them and dislodge them with a gentle tap. Some folks find the hand-held vacuum cleaners a nifty solution. Or if you’re feeling brave, grasp firmly by the antenna and fling quickly out the door.

Stink friends were once limited to the Rocky Mountains, but their range seems to be spreading rapidly. Extension offices all the way to New England are starting to get inquiries about these household visitors—and their advice is along the lines of what I dispense: “Oh, you have stinkbugs…? Aren’t you lucky to live in a forest!”

Carol Mack
WSU/Pend Oreille County Extension
cmack@wsu.edu