Likely larva of common eastern firefly, but it’s the first time I’ve noticed one of these, so I’m not totally sure. Found several inches down in damp garden soil.
Lucidota atra is a day-flying firefly that glows as a larva -- and as a pupa, obviously! -- but not as an adult. (Don't ask my why! What is is glowing for, if not in order to find a mate?) Found it in decaying leaves while gardening. Looks pretty far along, & in fact I observed adults in the area the following day.
8.7 mm long (measured in this position, not uncurled).
Found in DeSoto State Park, by the hundreds. Along cabin road, found near the Lodge. Observed May 3rd and 4th(2018)