Isopods are not insects but crustaceans. They are relatives of insects however, with their jointed legs and exoskeleton. Actually they are more closely related to shrimp, crayfish and crabs. They are probably native of Europe and were introduced into North America several centuries ago. Numerous species are common throughout the U. S.
Although most isopods are aquatic, Many are terrestrial in habit. Two groups that are familiar to most are the pillbugs and sowbugs.
Pillbugs and sowbugs are somewhat flattened dorsoventrally and very convex. They are distinctively segmented, have seven pair of segmented legs and a pair of segmented, antennae-like projections at the head end. They range in color from a grayish brown to a dark slate gray.
Sowbugs have a pair of tail-like projections at the end of their abdomen. They cannot roll up into a "ball". Pillbugs will roll up into a "ball" when disturbed. Pillbugs do not have tail-like appendages
You find both pillbugs and sowbugs in areas of very high moisture where there is an abundance of decaying organic matter. They feed mostly on decaying organic matter but some will feed on living plant tissue. They generally feed at night and hide during the day to avoid the light and to keep from drying out. They are often found huddling together in great masses in an effort to reduce evaporation rate.
Isopods lay eggs. And they may lay two to three batches in a year. Each female can lay up to about 300 eggs. Their eggs hatch in about 50 days. Newly hatched isopods take about one year to grow to maturity. Adults live for about two years.
A few species can be a pest of cultivated crops. They occasionally invade homes but do not damage the home or its contents. They can not survive very long in doors.