Home Hibernators

Being a bug during the winter isn’t easy. Insects have to develop ingenious ways to avoid the cold temperatures, because they cannot regulate their internal temperatures, like we can. Some strategies are to join up with other bugs and aggregate in an overwintering site. Having many individuals massed in a protected nook can increase the chances for surviving the winter. For example, many ladybugs aggregate to form a large mass and hide out in a fallen tree or rock. Individual beetles fidget their way to the center of the mass, where it is warmer and more protected. This proves to be a great feat of nature but is unfortunate when it happens in your house.

A few insects commonly annoy Whatcom County residents every year by their overwintering habits. The most common house invaders are Asian lady beetles (Harmonia axyridis) and western conifer seed bugs (Leptoglossus occidentalis). A few other types of true bugs in the order Hemiptera also like to overwinter in homes. Most of these are called ‘seed bugs’ and are in the family, Lygaeidae. Our state entomologist, Eric LaGasa, is watching the movement of a new seed bug that is harassing people in Puyallup (http://whatcom.wsu.edu/pestsurvey/Alertrhyparochromis.htm).

Multicolored Asian lady beetles were imported to control aphids in tree fruit production. Now, these lady beetles have spread across the US and cause many people annoyances during the winter. Asian lady beetles come in all different colors ranging from black to red and orange, with as few as two spots or as many as nineteen spots. These ladybugs can be difficult to distinguish from other native ladybugs. In the fall, Asian ladybugs will start to swarm and collect on the southern exposures, often on a nice bright wall of a house. As temperatures cool, the beetles make their way inside through cracks and gaps in windows and walls. Once inside, ladybugs become active in the warmer temperatures bouncing around in light fixtures. Ladybugs can pinch and irritate skin. They also ‘reflex bleed’ when disturbed, producing an unpleasant smell.

The western conifer seed bug is actually in a family of true bugs called ‘leaf-footed bugs,’ or Coreidae. This species is a large, robust bug with long legs. As with all true bugs, L. occidentalis has a piercing-sucking mouthpart and a half leathery, half membranous wing called hemielytra. This leaf-footed bug can bite (although rarely) and also produces an unpleasant smell when disturbed. As with Asian ladybugs, the conifer seed bug aggregates on southern exposures and eventually makes its way inside through cracks in the wall or broken screens.

With winter just around the corner, I’m sure many of you have already seen these critters lining up to get inside your house. Some simple methods can be used to keep them outside. Seal up any cracks or crevices on your house with caulk or weather strips. Be sure to pay close attention to the southern or southwestern walls of your house. Make sure that windows are sealed tightly and broken panes or screens are repaired. Look closely at your attic and check the screens of the ventilation in the attic. Ladybugs often gain entrance to the house through the attic.

If large numbers are collecting on the side of your house, make life difficult for them. Hose them off regularly or get out the shop vacuum and clean them off the walls. If large numbers of these insects are inside your house, be diligent in disposing of them. Using a vacuum is effective but may cause some short-term odors. Vacuum insects as you find them. In my house, I find them mostly in windows towards the end of the day, and this is where I concentrate my cleaning efforts. If large numbers are in the attic, consider using a black-light trap. Light traps can be very effective for catching large numbers of ladybugs.

It is not recommended to use pesticides inside or outside the house. Using an insecticide inside the house may cause more pest problems. If large amounts of insects are killed, but not disposed of inside the house, other pests like carpet beetles or mice will flourish on the insect carcasses. Using insecticides outside the house is a preventative treatment and may not be necessary. Insecticide applications to outside walls cause mortality in many beneficial insects, just stopping to warm up on the sunny wall.

For more information: see Art Antonelli’s PLS 90 and Dan Suomi’s PLS 114.