Pill Bugs and Sow Bugs are types of pests that look very similar, but they are not totally the same. Most times, you find them in the garden. Pill Bugs and sowbugs are great decomposers because they feed mostly on decaying materials. If they are present in a large proportion in the soil, they can cause more damages as they will be feeding on the roots, seedlings, and vegetables. One major difference between pill bugs and sow bugs is how both tend to protect themselves when threatened.
When a pill bug is threatened or gets agitated, it has the ability to easily roll itself and turn into what looks like a ball. This is possible for pill bugs because of the nature of their body. Sowbugs, on the other hand, do not have this type of ability; they can't roll into a ball during emergencies. Another difference is in the arrangement of their body.
Pillbug can curl up its entire body into forming a ball with their legs tucked inside to defend itself while Sow bug does not have this ability to roll into balls but produce lots of harmful defensive chemicals. Pillbug doesn’t have any structure that looks like a tail, while a sow bug has a structure at the rare end part of its body that looks like a tail. Pillbug has a rounded back from each side with a deeper body from it’s back to legs, and it has a blue ting on its brownish gray colored body reaching less than 2.5cm (1inch) in length at maturity.
On the other hands, Sowbug is land crustaceans, having an oval body when viewed from above. It has an overlapping back called articulating plates with a grayish color, and they grow to about 15mm long (9/16 inches) and 8mm wide ( 5/16 inches).