Hellgrammite (Dobsonfly Larvae) (Corydalus cornutus)

Other Names

Eastern Dobsonfly

Description

Hellgrammites grow to a length of 2.75 inches (7 cm). They have yellowish to brown, stout, segmented, caterpillar-like bodies, large pinching mandibles, six legs on the thorax, eight feathery appendages on the abdomen, and four claws at the rear of their abdomen.

Life History

Hellgrammites consume aquatic insects and small invertebrates, and are eaten by fish, frogs, other aquatic predators. They are nocturnal (active at night). Hellgrammites are also poor swimmers, but voracious predators. To catch prey, they hide under large rocks and other shelter in fast flowing stretches of streams, creeks and small rivers and attack prey as it swims or crawls past.

It can take up to three years before they reach sexual maturity. Mating begins immediately after emergence from the pupae stage as dobsonflies, from April through May. Up to 3,000 eggs are contained in each egg mass. Eggs are produced from May through August. Females lay circular egg masses at night on rocks, leaves, trees, bridges and other suitable sites that hang over water. When the egg masses dry, they look chalky and white.

Each female lays two egg masses during her two-week long adult life. The eggs incubate for two weeks. After hatching, the larvae, hellgrammites, drop into water. Hellgrammites hide under rocks in streams. They can stay in this larval stage as long as four years, but usually only two to three years. Hellgrammites may shed their exoskeletons as many as 12 times before they emerge as pupae. The pupae crawl several feet onto land and burrow 2 to 4 inches (5 to 10 cm) into wet soils, moss, decaying vegetation or beneath rocks and logs. They emerge as dobsonflies two weeks later. As hellgrammites, larvae live two to three years. As dobsonflies, adults live about two weeks.

The short-lived adult dobsonflies are among the largest flying insects in Texas. Dobsonflies are reddish to grayish brown with strongly veined wings and small white spots on their forewings. They have long, thin antennae. Their bodies are about 5 inches (13 cm) long with a wingspan of 4 to 5 inches (10 to 13 cm). Male dobsonflies have long, sickle-shaped, pincer-like jaws up to 1 inch (2.54cm) which are used to grasp females during mating. Adult dobsonflies are terrestrial and seek shelter in tree canopies near water. They hide by day under leaves, are weak fliers and are attracted to lights. They are nocturnal. Adult dobsonflies don't eat, and after mating, they die.

Habitat

This species is aquatic and lives in the shallow, fast flowing portions of streams, creeks, and small rivers, hiding beneath rocks and logs.

Distribution

Hellgrammites range throughout North America.

Other

Dobsonfly larvae make excellent fish bait and are often used as such, especially for largemouth bass. But be extremely cautious when handling hellgrammites because they bite. For that reason, they are also called "toe biters".