Woodlice / Pillbugs & Sowbugs
If you have ever poked a gray, armored creature scuttling across a damp basement floor only to watch it curl into a neat little ball, you are looking at a terrestrial crustacean that is actually more closely related to shrimp and lobsters than to any household insect. Known as pillbugs, sowbugs, or woodlice depending on where you live, these land-dwelling creatures are unified by their strict need for moisture, their seven pairs of jointed legs, and their slate-gray armor. Some varieties can roll themselves into tight spherical roly-polies when startled, while others stay flat and display two tiny tail-like appendages at the rear, but all of them share a complete lack of wings and a total dependence on dampness.
Telling them apart from actual insects and other basement wanderers is straightforward once you count the legs and look at the body shape. If the creature in front of you has thirty or more legs and an elongated worm-like body, you are looking at a millipede or centipede instead of an isopod. If it has only six legs and a tapered, scaly body with three long tail bristles, you have a silverfish. Woodlice hold a middle ground with fourteen legs and a flattened, oval shell, and they cannot survive for long in dry indoor air. Finding them indoors usually just means a nearby door seal is letting moisture in or a mulch bed is pressed right up against the siding, rather than pointing to a destructive infestation.
