Bristle Millipede (Genus Polyxenus), taken March 21, 2025, in Georgia, US
A tiny, spiky millipede! Despite this guy's small size, this is actually the largest bristle millipede I've seen. Usually I find juveniles, which just look like fluffy balls due to them having less segments. On this guy, however, you can see the individual rows of bristles lining each segment!