The dobsonfly, Corydalus cornutus, is a long, dark-colored insect of North and Central America, that spends most of its life in its larval stage. The larvae are called hellgrammites, live under rocks at the bottoms of lakes, streams and rivers, and prey on other insect larvae. Hellgrammites are used by many fishermen as bait, though this practice may stem, more than anything, from the challenge of catching a hellgramite without being bitten.

Dobsonflies have large, powerful jaws, and in the case of females, are capable of drawing blood from humans. Though both male and female hellgrammites have short, sharp mandibles, those of the male dobsonfly are much bigger than the females' and are unable to harm humans, as they're so long and flexible that they are incapable of breaking the skin. They are used exclusively for grasping the females during mating. Female dobsonflies, however, retain the short, powerful pincers they had as larvae, so they can inflict painful--albeit nonvenomous--bites. When threatened, they will raise their heads and spread their pincers menacingly. They also possess an irritating, foul-smelling anal spray, as a last-ditch defense.

After a few years of living and growing underwater, the larvae crawl out onto land and pupate. They stay in their coccoons over the winter and emerge only to mate. Upon emerging, they live for only a few days. While not generally believed to eat during their adult stage, some captive, female specimens have been observed with their heads burrowed into blackberries.

Both male and female dobsonflies can reach lengths up to five inches, measured from the tips of their pincers to the tips of their wings, which, when not in use, are folded along the length of their walkingstick-like bodies. Their wingspans--four wings in all--can be twice as long as their body length, and the wings themselves are densely lined with intersecting veins. As a whole, their bodies are rugged, stout and strong, giving them excellent chances for survival, both as larvae and as adults.

They can generally be found from late spring into the middle of summer, preferring to remain near bodies of water, particularly the ones from which they came, because their sole purpose once they emerge as adults is to mate, deposit their eggs near the water (often on overhanging vegetation), then die.

External links/Sources

• http://www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/dobsonfly.htm
• http://mbgnet.mobot.org/fresh/slide/dobson.htm
• http://insects.tamu.edu/fieldguide/bimg121.html
• http://tolweb.org/tree?group=Corydalus&contgroup=Corydalinae
• Dobson Fly page at "What's That Bug"
• Hellgrammite page at "What's That Bug"

Flies | Corydalus cornutus