Hellgrammite (aquatic larval stage of the Dobsonfly)

Dobsonflies spend most of their life in the larval stage, during which they are called hellgrammites, and are familiar to anglers who like to use the large larvae as bait. Hellgrammites live under rocks at the bottoms of lakes, streams and rivers, and prey on other insect larvae with the short sharp pincers on their heads, with which they can also inflict painful bites on humans. The larvae reach to 2" to 3" in length, with gills all along the sides of their segmented bodies that allow them to breathe underwater. Their gills, primitive nervous systems, and hard, segmented bodies mean that once hooked, hellgrammites can survive for long periods wiggling underwater. In the Appalachians, children catch these for fishing bait as a test of courage, working their fingers into the mud under rocks until a hellgrammite bites, then grabbing the creature with the other hand and throwing it into a jar. A less painful way to catch them is to stretch a mesh net across a narrow point in the stream, forcing the net to the bottom, then have others upstream turn over rocks and disturb the creek bottom, forcing the hellgrammites into the streamflow so they are carried into the net, whence they can be plucked and put into bait buckets. South Texas tradition has it that the name comes from a child asking if the larvae will bite, the obvious answer, "hell, it might." -Wikipedia