| any of certain small, terrestrial crustaceans of the genera Oniscus, Armadillidium, etc., having a flattened, elliptical body. |
| pill bug n. In both senses also called slater, wood louse; also called regionally doodlebug.
Usage Note: Many people, especially science teachers, like to make a distinction between pill bugs and sow bugs. According to this usage, a pill bug, or roly-poly, is a terrestrial isopod crustacean whose segmented body gives it the ability to curl up into a ball when disturbed. A sow bug is any of several similar looking creatures that lack this ability. In popular usage, however, the names pill bug and sow bug, along with a number of other popular names, are used to refer to any of these tiny segmented crustaceans that are often mistaken for insects. |
sow bug  (sou)  n. In both senses also called slater, wood louse; also called regionally doodlebug.
[From its piglike shape.] |