As we head fully into fall, you may begin to notice that a few “house guests” have joined you in your home. I like to call these guests “accidental invaders,” but most people call them insects –  or pests.

They come in a variety of sizes, shapes and colors. The main reason they show up in your home is to overwinter and avoid harsh winter conditions. Not unlike us, they would rather spend the winter in a nice warm, comfy environment than be outdoors, subjected to severe cold temperatures.

Here’s a look at a couple of the more common invaders, and some practical suggestions on how to co-exist with them and still enjoy the winter months.

UNINVITED GUESTS: There are several ways to keep overwintering pests out of your home this winter. (Photo: Xurzon/iStock/Thinkstock)

Boxelder bugs
These insects are quite common and will occur in large numbers, particularly where boxelder trees are prevalent — which is just about everywhere. Adults and nymphs will congregate on the sides of houses and other structures in late fall where they can bask in the sun. Once temperatures drop, they will move indoors to overwinter. The adult boxelder bug is gray and red, and has a triangular shield on its back. The nymphs have wing pads or lobes and are bright red, developing gray markings as they mature. They like to hang out around windows, behind drapes and in other secluded sites. They are harmless, but will stain fabric if crushed. One way to reduce their numbers, before they come indoors, is to douse them with soapy water when they are congregated on the sides of structures. Once indoors, they can be vacuumed or swept up and shown the door. Use of indoor insecticides is usually not warranted or justified, as you would need to treat your entire home. Once spring arrives, they will leave for the summer.

Multicolored lady beetle
This insect was introduced into the Midwest to help control soybean aphids. It looks like a typical ladybug, is multicolored, and has a variety of spots. The big complaint with the lady beetle is that it tends to nibble on folks. I remember having my family at a local forest preserve and they were pretty annoying — even for me, an entomologist.

They may become active on warm winter days, especially in west- and south-facing windows. Like boxelder bugs, they pose no threat to us or pets, but may secrete a chemical when crushed that can stain fabrics. There are some cases where large numbers of dead lady beetles may contribute to allergies, but that is common with just about any accumulation of dead insects. Vacuuming is usually effective. Their willingness to feed on the soybean aphids and provide growers with free biological control more than outweighs their annoyance.

If your situation merits control, here are a few recommendations:

• Caulk and seal all openings to help prevent them from coming in.

• Keep screens on windows, and keep doors closed as much as possible.

• Insecticide perimeter sprays on the structure's foundation can be used in extreme cases (most effective prior to combining nearby soybean fields).

• Consult with your local Extension office for specific products and use. 

• Use products as labeled, including using outdoor products only outdoors and vice versa.

• Spraying the interior of the house is not recommended — and is not very effective once the insects are inside.

Do not a few overwintering house guests ruin the enjoyment of your home. Even though they may stay a while, like in-laws and “outlaws,” they will leave after a time. If you need additional information concerning household pests, consult your local Extension office.

Miller is a horticulture professor at Joliet Junior College, Joliet, and a senior research scientist in entomology at The Morton Arboretum in Lisle. Email your tree questions to him at [email protected].