text: what is a sow bug? i have these little gray bugs running around in my garden.  are they harmful? the sowbug, also known as the pillbug:  they are dark brown to grey.  they can grow up to 3/4 of an inch.  they are much wider than they are high.  they have 7 pairs of legs.   not to you, or your garden far as i know  they have 2 pairs of antennae, one is usually longer