Centipedes and millipedes are usually found outdoors in Illinois. However, during periods of extreme weather, such as excessive rain or drought, they can sometimes decide to invade a home so that they can search for food. Outside of the home, centipedes and millipedes can be found in dark and damp places. They tend to hide beneath piles of leaves, and they can often be seen when a rock is overturned. Outdoors, these insects are fairly harmless, although they can cause trouble for gardeners and farmers when they decide to feed upon fruits and vegetables, such as cucumbers or melons. When they do decide to enter a home, it is typically in a large migration of centipedes or millipedes that are looking for food. This means that when one centipede or millipede enters a home, then many others quickly follow. This can lead to a major infestation of these pests getting out of control rather quickly.