Sharing Your House for the Winter

It happens all the time. You are minding your own business, feeling that onset of colder nights and shorter daylight hours, when all of a sudden you notice a beetle. Then another one. Then a bunch more, and maybe thousands, all of them running around on your family room floor and trying to hide under things.

Or, it could be flies, or ladybugs, or grass bugs, or any one of many other kinds of insects that decide your house is the chosen one on the block where they and their friends will spend that winter. Why they chose your house, if this is your first encounter with them, is difficult to say, but here they are. It may be the exterior color, a certain light exposure, the way the trees are arranged in your yard, or some other stimulus known only to the bugs. If they have visited your house in large numbers in past years perhaps the attraction is odors left behind by their ancestors, signaling that your house is a great place to be in the cold months of the year.

All animals survive the winter somehow. In Florida, southern Texas, or southern California there generally isn't a huge problem, as many areas of the country or the world have moderate temperatures all year long, and the animals may just remain active. Even in these climates there may be Dry Season and Wet Season, and the animals may go semi-dormant at some point. However, in most of the United States and other "temperate" climates the winters tend to get very cold, and insects in particular cannot survive if they remain active and exposed.

So, they hide. It may be in the adult stage, as with many butterflies such as the Mourning Cloak, or with the flies, beetles, or "bugs" that invade your home. It may be in the pupa stage, as with the Tomato Hornworm moths, that bury themselves in the soil in your garden and change to a pupa for the winter. It commonly is in the egg stage, as with the Praying Mantids, whose large egg masses are found on the stems of bushes or rails on your fence. Sometimes it may even be as a larva, that goes into hibernation and remains motionless for many months.

Generally, it is the adult insects that are your problem, and many species of different kinds of insects are well known for their inclination to invade structures, often by the tens of thousands, perhaps gathering on the walls outside first, and then squeezing in through tiny openings to collect in the wall voids, attics, crawl space, or other hollow places they may find. And, unfortunately, what goes in must come out, so if you endured the Invasion of the Insects in the fall you likely get to enjoy the Exodus of the Insects in the spring, when it warms up and reactivates the dormant animals.

There are two primary causes when you see a lot of bugs in your home at a time of year when they just should not be active. We have been discussing the first, that of insects choosing your home as their favored hiding place. The other is also very, very common, and also easily cured. That is our inclination to bring firewood into the house far in advance of burning it in the fireplace. Often this is wood that was cut down the summer before - perhaps some trees removed to make way for a housing development, or perhaps an old oak tree that simply died for some reason.

Nature is bound and determined to recycle everything, and trees are some of the first to be occupied by the decomposers once they have died. Beetles find the recently deceased trees and lay their eggs on the bark. Their larvae then eat the dead wood inside, and in many species they go into their pupa stage in the late summer, awaiting the warmth of spring to trigger their emergence as an adult beetle. If we bring firewood into our house that has these larvae or pupae inside, that wood begins to warm up, and the insect instinctively feels that spring is here, and out it comes.

One of the very common beetles that occurs in homes in the winter because of its presence in firewood is the Nautical Borer, a kind of Long Horned Wood Boring beetle. They are about one inch long, black, and very active, running around on your floors and looking like a large spider. Not to worry though, because they are completely harmless to people, and cannot infest anything in your house, so a vacuum cleaner is your best method of dispensing with them.

Some of the other kinds of bugs, though, that use your attics and walls as their winter home, are these:

  • Flies - cluster flies, face flies, blow flies
  • "Bugs" - leaf footed bugs, stink bugs, grass bugs, assassin bugs, box elder bugs
  • Beetles - ground beetles, ladybird beetles, elm leaf beetles

Let's pick a few of these visitors and take a little closer look at them. One of the guests that is so commonly found around the United States is the Cluster Fly. As flies go, this species is fairly large - a little bit larger than our common House Fly - as it gets its common name from this nasty habit of "clustering" in large groups inside our buildings. Unlike so many of the other pesky flies we are annoyed by, where garbage cans or dead animals are the places where their larvae may be found, the Cluster Fly lays its eggs on the dirt in your backyard. When the eggs hatch the young maggots seek out earthworms as their food, and live as parasites in the worms for a couple of weeks.

Since we cannot do anything to control the source of the larvae, we must concentrate on keeping the adult fly out, and that can be difficult. The Cluster Fly is identified by taking a very close look at its thorax, perhaps with a strong magnifying glass. What you will see is a fine layer of curled, yellow hairs all over the thorax. This is the only fly that has such a feature. Another characteristic, and an annoying one, is their habit of flying around in a very sluggish manner when they emerge from hiding, and they may bump into you or just flop themselves down onto the table where you are sitting with your lunch. They may often be found just sort of "hanging out" on the walls or curtains, not at all active and not too skittish when you approach them.

Controlling cluster flies relies heavily on making it impossible for them to get into your home, and this means closing as many of the little openings as possible that they may squeeze through. The adults begin to gather on the outside of your home in the fall, and then look for little holes and crevices they can get through to get into the walls or attics. There may also be some methods that licensed pest control companies can offer, with their years of experience in dealing with these critters, so you may want to contact a company in your area.

Similar in their over-wintering habits are Face Flies (close cousins of the Common House Fly) and Blue Blow Flies - big, noisy, shiny blue flies that buzz around and audibly bump into lights. Both of these have larvae that feed on unsanitary, decaying organic materials, so controlling these sources will help to control the populations of the adult flies.

Another group that we will look at a little more closely is the "Bugs", and this is actually scientifically accurate, for a large group of insects is referred to as the "True Bugs". There are several kinds that I have seen on a regular basis, found in homes in the fall (entering), the spring (exiting) or in the middle of the winter on an unusually warm day or two, when the walls warm up enough to cause them to become active.

Probably most notorious among The True Bugs is the Box Elder Bug, common throughout much of the United States. It is a large insect, with the adults reaching around ½" long. They have gray wings and bright red bodies. Like the Cluster Fly they are not great flyers, and are likely to fly into your face as they move about. While this is frightening these insects are not dangerous to people. Like so many of their relatives in the group of True Bugs, box elder bugs smell bad when they are crushed, so stepping on them inside your house probably is not a good idea.

Their habits are very much the same as the other winter guests. They pick a particular house - for reasons known only to them, and begin to gather on the outside walls in the fall. Apparently the presence of some serves to attract others, and now you have a growing problem. You might also be the source of box elder bugs. They feed on plants, and in particular like Box Elder Trees and maple trees, so you might check these trees in the summer to see if you are harboring and breeding populations right in your own back yard.

In the western U. S. there is a related bug called the Grass Bug, and it is found very commonly in homes in the fall and spring. It acts much like box elder bugs, but is smaller and is a dull gray to grayish green color. In the case of these kinds of plant feeders a professional pest control company may very well be a great help in reducing the numbers of the bugs in the garden in the summer, so that you have a far smaller problem to be concerned with later.

Another member of the group called true bugs, and one also commonly found in homes on warm winter days, is the Leaf Footed Bug. Its habits are similar to the others we mentioned earlier, but it is much larger. It also bears a close resemblance to some bugs called Assassin Bugs, that are biting bugs and are somewhat dangerous to have around. However, the Leaf Footed Bug is easily distinguished by the white, wavy lines across its wings, and by the widely expanded section on its hind legs. These are plant feeders, and will not harm people or animals.

A third winter guest is the Ground Beetle, and there are many kinds that may be likely to choose your home as the lucky one. A problem with these beetles is very similar to the problem we discuss in another BugInfo on Ladybugs, and that is that all ladybugs, and almost all ground beetles, are predators of other insects and thus are considered "Beneficial". Now, beneficial is a relative term, for when these important insects are invading your home in large, active numbers, you generally lose your love of them and just wish them gone. There frequently are occasions when they will seek winter shelter in a very sensitive situation, such as a hospital, and then they truly present a liability to have around.

The most common kinds of ground beetles to have as over-wintering guests are some of the smaller species. I suppose we at least have that to be thankful for, for some of the larger species can be well over one inch long. Just imagine hundreds of those running around on your furniture. In the Central Valley of California there is one culprit called the "Tule Beetle", a very light brown variety. In other areas the common kind may be a dark brown one, and many other small species are solid black. As a deterrent to being eaten by other predators, such as birds, lizards, or frogs, most of the Ground Beetles have the ability to ooze out foul-smelling - and presumably foul-tasting - fluids. For this reason it probably is not a good idea to smash many of these insects in your home either.

These common beetle invaders generally cannot fly, so they rely on finding their way in on foot, crawling under doors and through window sills, or through the vent screens that cover the holes into your home's crawlspace. You can do yourself a great favor in keeping their populations around your home at low levels, by maintaining the yard area as free of piles of lumber or yard trimmings as you can. Anything left sitting on the ground offers shelter for the beetles, as well as for the critters the beetles may feed on, and can encourage their presence and their ability to build up their numbers.

Ladybird Beetles, or "ladybugs", as they are more fondly called, are another growing nuisance in our homes. We have written a separate article just on these beneficial critters, so look for that in BugInfo too.

So, if you suddenly find yourself with lots of unwanted and unexpected traffic in the house, at a time of year when that traffic is supposed to be sleeping, these could be some of the reasons.