A recently deceased caddisfly larva. Caddisflies make up the order Trichoptera, and are closely related to butterflies and moths (order Lepidoptera). The larvae are aquatic, and some make cocoon-like cases out of debris to shield their bodies as they roam the stream bed. There is, however, no specific family that I'm aware of that makes these "cocoons". It seems to vary by species.

This one came from somewhere in North Dakota, in or not far from Burleigh County, in May. I believe this one is from the Phryganeidae family; the "giant case makers". Both the larva and its case look very much like a Agrypnia or Phryganea species, however, I am not sure if they are present in ND. There are several species of Agrypnia in Saskatchewan though, which is north of us. It is also possibly Fabria inornata the only member of the Fabria genus to occur in North America (including ND). The case does appear to have the spiral construction of the genus, and not the ring construction of some other genera in the family. It also has the correct "forehead" pattern of a Fabria.