Now that the weather’s getting cooler, I’m starting to see some of those strange bugs moving into my house again. You know, the ones that supposedly spend the winter indoors and then move out again. How do we know these bugs aren’t going to just stay inside and breed? L. S., Hamilton, MA

Most of the so-called “fall-invading insects” feed on various plants or crops outdoors so, first of all, there would be nothing in your house for them to feed on long-term. Western conifer seed bugs, brown marmorated stink bugs, boxelder bugs, etc. all suck juices from plants. One of the reasons that fall invaders seek winter shelter is that their food plants have died or gone into diapause, and the other reason is…well, winter is cold and wet. These insects are looking for a protected place to get out of the elements until they can return outside in the spring to mate, reproduce, and complete their life cycles.

While there are certain pests that are adapted to living and reproducing inside such as cockroaches, silverfish, and spiders, the plant-feeding insects that move inside in the fall are just not cut out to be indoor dwellers. They don’t really want to be inside. Your cozy home just happened to be in the right place at the right time, and it had little openings that invited them in (see Outdoor Insects Are Getting Ready to Move Inside!). Because overwintering insects will stop feeding and enter an inactive state for several months, they can temporarily survive indoors.

WINTER DRYNESS WILL KILL MANY INVADING PESTS

The biggest roadblock to inside survival for most outside invaders is moisture, or lack thereof. Most insects and other arthropods require high humidity and seek areas of higher moisture such as under mulch or bark. Many creatures, for example millipedes, earwigs, and sowbugs, that accidentally wander inside live in damp areas around building foundations. These invaders require high humidity and usually die within a couple of days in drier indoor air. Even if the indoor environment provides the food they need, conditions are just not right for them to survive.

KEEP THE BUGS OUT IN THE FIRST PLACE

Outdoor insects that move into your home in the fall are going to be a temporary nuisance. With some plant-feeding pests and in some years, large numbers may move indoors but you may not even see them again until warmer spring weather rouses them. Sometimes an extra warm spell in winter will fool them into thinking it’s spring and they may emerge from hiding looking for a way to get outside.

There are things you can do to keep fall invaders out in the first place such as cleaning up debris around your foundation, pest-proofing your home by sealing openings, and contacting Colonial Pest for a pesticide treatment around the outside perimeter of your home (see Take Steps Now to Keep Fall Pests Outside!). Once fall invaders are inside and in hiding, control is very difficult.