Sowbugs and pillbugs are the only two crustaceans that have adapted themselves entirely to land. They actually have gills instead of a trachea (insects lungs) with which they breath.
They are also related to snails and slugs.
Sowbugs are virtually the same as pillbugs but have a wider body and cannot roll themselves into a ball. Sowbugs have two appendages that protrude from the rear of the body. They have oval bodies which have 7 overlapping plates, as well as 7 pairs of legs. Head and abdomen are small compared to rest of body and they can reach 3/4 inch in length. Pillbugs  can roll up into a tight ball.

Both are scavengers which feed on decaying organic matter and can injure young plants. They like moist locations and are found under objects on the damp ground, as well as under vegetable debris of all kind. They may bury themselves several inches into the soil and are active mostly at night.

Sowbugs and pillbugs require about a year to become fully grown. Most breeding occurs in the spring, but may occur throughout the year. One to three broods are produced yearly with 25 to 200 young per brood. The female carries the young in a brood pouch underneath her body. The young remain in the pouch for 1 or 2 months after hatching. The life span is about 2 or 3 years.

Control:
Pillbugs and sowbugs are best controlled by eliminating the moist environment that initially attracts them. Piles of organic matter, dense ground cover near foundations, or ground level windows, boards, stones, flower pots, firewood, and other materials resting on the ground, serve as food sources, and harborage areas for pillbugs and sowbugs and they should be removed or modified to reduce the pillbug or sowbug population.

Entry into building should be prevented by sealing and caulking gaps around siding, windows, doors, pipes, wires, etc. Large numbers of these structure-invading pests are easily controlled by vacuuming and discarding the collected material. Unfinished basements and crawlspaces should be well-ventilated to reduce moisture which is attractive to these pests.

 Registered pesticides for Sowbug and Pillbug control vary from state to state.

Links:
Isopod, Pillbug, Sow Bug Information

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