Corydalus
"Dobsonfly"

This common name applies to any member of about 200 species worldwide in the genera Corydalus, Chloronia, or Platyneuromus. They are found in many temperate regions, with the exception of Europe, neighboring Asia, and nearly all of Africa. The species Corydalus is the best known of the American dobsonflies. Thirty species of Corydalus are currently recognized with 22 species found solely in South America. Species of Corydalus in Central and North America are C. luteus, C. magnus, C. bidenticulatus, C. texanus, and C. cornutus. C. cornutus is probably the most common in the United States. Corydalus species are widespread throughout North America. The dobsonfly is the adult form of the common aquatic immature called a hellgrammite.

Hellgrammites, the larval stage of dobsonflies, occur under stones in non-polluted, fast-moving, well-oxygenated streams. Hellgrammites can swim, but usually crawl, and live 3 to 5 years before maturity. They can grow up to 9 cm (3.5 inches), and can inflict a painful bit if mishandled. The safest way to pick up a larva grasp it directly behind the head. Wading children call them "toe-pinchers". The larvae have a head with large pinching mandibles, short antennae, six legs on the thorax, and eight pairs of appendages on the abdomen. Brush-like gills occur at base of each appendage. At the rear of the abdomen there are two short appendages, each with two claws. Hellgrammites feed on tiny aquatic organisms, and in turn are fed on by fish, frogs, and other predators. Hellgrammites are a sought after bait by fishermen as trout love them. Dobsonflies undergo complete metamorphosis. After the egg, hellgrammites go through up to 11 larval stages lasting a total of 3 to 5 years. At that point, they emerge to excavate a pupal chamber in moist sand, soil, or moss beneath stones or driftwood. They may remain there for several months in the larval stage, before actually pupating. Pupae remain mobile and can protect themselves with their mandibles. Whereas, the aquatic immature spends several years in a stream, the adult dobsonfly lives only about 7 days. Hiding under leaves during daytime, females can be located a night (May to June) ovipositing near streams. Their chalky white egg masses can be seen in daylight. Hatched larvae fall directly from eggs into the stream to start the cycle again.

Adults are up to 120 mm (4 ¾ inches) from the front of the head to the wing tips and are soft-bodied and brownish in color. The adult possesses two pair of large wings that are similar in size, with many cross veins and a white dot in each cell of the wing. Wings are held roof-like over the body at rest. The female is an effective biter if given the opportunity. Females have short inconspicuous mandibles while the male has long, sickle-shaped mandibles about ½ the length of his body. The male uses his sickle-shaped mandibles to grasp the female during copulation. Adult dobsonflies probably do not eat.

Adults are up to 120 mm from the front of the head to the wing tips and are soft-bodied and brownish in color. The adult possesses two pair of large wings that are similar in size, with many cross veins and a white dot in each cell of the wing. Wings are held roof-like over the body at rest. The female is an effective biter if given the opportunity. Females have short inconspicuous mandibles while the male has long, sickle-shaped mandibles about ½ the length of his body. The male uses his sickle-shaped mandibles to grasp the female during copulation. Adult dobsonflies probably do not eat. The 4 and 3-segmented maxillary and labial palps, respectively, are a generalized diagnostic trait for the genus, Corydauls.

Gwendolyn Fleitstra and Andy Harmon
Entomology 301 - Fall 2000