Late summer is the time when a number of insects and spiders start to make "plans" for the winter! And those plans often include spending several months in a rotective corner around the outside or inside houses or other structures. In general, these insects overwinter as adults and must find harborage that will provide protection from low temperatures and low humidities of the season. The list of overwintering (but usually uninvited) house guests includes several species of mosquitoes (mated and unmated females), beetles such as the elm leaf beetle and the Asian or Japanese ladybird beetle (cute but too much!), boxelder bugs, cluster flies and face flies that get into the attic, and a few species of spiders, including wolf spiders (not cute at all!). In spite of our efforts, there may be little we can do to prevent at least a small number of these arthropods from utilizing the outer or inner confines of the house during the cold months. But prudent yard work and perhaps a preventative spray around the outside may deter some of them. Some of these insects are regular house invaders, and occur year after year--such as cluster flies, and now the Japanese ladybird beetles. Some are unpredictable and may occur one year and not the next--such as boxelder bugs and leaf beetles. Their occurrance is linked primarily to population fluctuations and to some extent the summer weather.
Elm leaf beetles. These small black and brown beetles can occur in large number in the fall. They often overwiner in house attics and leaf litter close to infested trees. Their larvae feed on the leaves of elms (a large group of trees) and can become a nuisance as they riddle the leaves and cause them to drop during the summer. There is not much that can be done to control them when on the trees, since they can be very numerous and the infestred trees very large. And there is little that can be done to limit their overwintering habits.
Boxelder bugs. The last summer generation (the second or third) of the black and bright red boxelder bug will be looking for a winter harborage in August and September. These insects also utilize trees as a food source; they have sucking mouthparts and feed on the leaves, stems, and the seed pods (only on female boxelder trees). The early fall generation leaves the trees and moves to protected locations around houses to spend the winter. They often gather in large numbers--massess of boxelder bug adults and some large nymphs--and can be a serious nuisance. They are easily controlled with the use of insecticide sprays, but because of the large numbers applications may have to be made several times.
Cluster flies. These house fly lookalikes are common pests in Virginia. The immature stages feed on earthworms and there are probably three generations per year. The adults of the August/September generation seek the attics of buildings to spend the winter. During warm days in December and January some of the adults become active and fly to windows. Because they have limited energy reserves they die and may collect in large numbers at doors and windows. It is difficult to prevent the adults from accessing the attic, since they squeeze through narrow openings.
Asian or Japanese ladybird beetles. These ladybird beetles are quite variable in appearance. Individuals can be any color from pale orange to red, and have from no to more than 20 black spots. They are very hardy insects and the adults may live up to three years. This beetle and it aphid-eating immature stages inhabit many species of trees, including maple, walnut, willow, and oak. Although they make a contribution to the control of aphids on ornamental and fruit trees, the adults of this beetle can be quite a nuisance because of their overwintering habits. They often gather in large numbers in and around houses. In some cases there may be thousands of the adult beetles on the sides of houses. Control is very difficult, especially when there are so many of them; and caulking around windows and doors has only a limited impact on reducing the numbers that can enter the house.
The unusually wet weather in July this year has produced some interesting and quite pestiferous mosquito populations around the state (especially eastern counties). There has been an "August re-appearance" of several mosquito species that are primarily found in the spring breeding in temporary woodland pools. These pools are formed from spring rains, but dry in the summer and do not product mosquitoes. Not this year! Those pools have reformed in some locations, and provided the conditions for mosquitoes (oh, joy!). The tidewater region of the state has seen some problems from these "spring species" and problems from the usual species because of the storm waters in July. What all this may mean is that we could have some very bad (perspective is important here) mosquito problems next year. If large numbers of woodland breeding species lay eggs for hatching next year, and the species that normally occur in the summer have large populations and lay lots of eggs this fall--next spring and summer should see lots of hungry mosquitoes. So, all the more reason that homeowners should remove any and all standing water from their property now.