what is a hellgrammite?
Pictures Below â. Hellgrammites are the vicious larvae of the Dobsonflies, some of the only trout stream insects which pose a biting threat to the angler. The pincers of the adult are even more frightening that the larva's, and they're aggressive enough to use them once in a while. This family's life cycle does not create good dry fly opportunities, but the larvae may be eaten by trout year-round. They are a secret told only by stomach samples of well-fed trout.