Eastern dobsonfly (Corydalus cornutus) adult in summer, Ludlow, Massachusetts. The dobsonfly is an aggressive-looking insect with very formidable mandibles. The larvae, also known as hellgrammites, are aquatic predators that live in streams. Adults are short-lived, and probably do not eat. After leaving their larval stream and metamorphosing, they fly over nearby woods, and attracted to lights. Wild.