Rats are true omnivores and can eat everything from grains, vegetables and eggs to carrion. An adult rat is able to eat a third of its weight in twenty-four hours. Large cities are ideal places for them because there are large amounts of spoiled food and places to hide. In the wild, rats are active year-round and are usually nocturnal. They often occur in large numbers and always follow the same routes. Their home ranges may reach only 50 m in diameter, but for want of food they can travel 3-4 miles a night.
The House Mouse, the most commonly found mouse near humans through history, is an average 6 1/2 inches long and 8/10 of an ounce in Montana (Foresman 2001). The large ears are nearly bare. The short fur will be grayish brown above, with an underside that will be brown, gray, or even whitish, but never pure white, as in other mice of the same size (Ulrich 1986). Unlike most voles and mice, the tail is nearly uniform in color, top and bottom, and is scaly rather than haired.
In general cockroaches are flat and oval shaped with their heads pointing downward. They live in a wide range of environments, although most are attracted to warmer conditions such as those found in buildings or any average household. Most species of cockroaches are very sensitive to light and prefer darkness which is usually why they are found in dark corners of a house.
Often confused with the common house fly, cluster flies are roughly the same size. Some characteristics that differentiate the cluster fly: they fly somewhat more slowly than the house fly, they almost always fly toward windows on the warm side of a structure and their wings overlap almost completely, when at rest. Cluster flies are most common along the northern part of the US and in other countries around the world. They will appear inside homes only during the cool fall, winter or spring months.
While the boxelder bug can cause minor damage to its preferred host plant, the boxelder tree (Acer negundo), it is primarily a nuisance for the homeowner who finds large colonies of adults seeking places to overwinter. The boxelder bug will seek access to warm buildings through any cracks or crevices in foundations, doors, and windows, and it is their presence indoors that poses a nuisance. Although the boxelder bug neither bites humans nor spreads disease, the very act of trying to eliminate them is a major challenge.