HAIR WORMS: Nematomorpha

PHYSICAL CHARACTERISTICS

Hair worms are long and thin—2 to 118 inches (5 to 300 centimeters) long and 0.02 to 0.4 inch (0.5 to 10 millimeters) wide. They are black, brown, yellow, white, or gray. The front end of most of these worms has a white tip with a thin dark band behind it. Some hair worms have raised bumps on their surface. Young hair worms are parasites (PAIR-eh-sites) and live on or in other animals, or hosts, without helping them and usually harming them, but adults live freely.

GEOGRAPHIC RANGE

Hair worms live all over the world except Antarctica.

HABITAT

One type of hair worm lives in sea animals such as crabs and shrimp. The other type lives in insects such as crickets, grasshoppers, and beetles.

The worms that live in insects usually are found in slow-moving freshwater streams or ponds. In streams the worms are either attached to plants hanging over the banks or live between rocks on the bottom. In the sea, hair worms live anywhere from beaches to the sea floor.

DIET

Adult hair worms do not eat. Young worms absorb nutrients from their hosts.

BEHAVIOR AND REPRODUCTION

Adult hair worms that live in insects emerge from their hosts in late spring or summer. Some species mate immediately, but others wait a few months. After mating, females lay as many as six million eggs and then die. The worm larvae (LAR-vee) hatch from the eggs and bore into the larvae of water flies. When these larvae transform into adults, they fly to land, taking the hair worm larvae with them. The crickets and beetles and crabs and shrimp are infected when they eat flies containing hair worm larvae.

HAIR WORMS AND PEOPLE

Hair worms do not infect humans.

WHAT'S IN A NAME?

Masses of hair worms form large knots during mating. Hundreds of worms often can be found in a seemingly undoable tangle. For this reason, these worms sometimes are called Gordian worms. The Gordian knot was made by a mythical ruler who declared the person who untied it would be the leader of all Asia. Along came Alexander the Great, who sliced through the knot with one stroke of his sword.

CONSERVATION STATUS

Hair worms are not considered threatened or endangered.

NO COMMON NAME (Paragordius varius): SPECIES ACCOUNT

Physical characteristics: The color of Paragordius varius worms ranges from light yellow to nearly black. These worms are 4 to 14 inches (100 to 350 millimeters) long and about 0.03 inch (700 micrometers) wide. The tip of the male's tail is split in two and the tip of the female's tail in three.

Geographic range: Paragordius varius (abbreviated as P. varius) worms live in North and South America.

Habitat: Adult P. varius worms live in and near slower streams, puddles, and places where rain water collects. The larvae live in crickets and grasshoppers.

Diet: P. varius larvae absorb nutrients from their hosts. The adults do not eat.

Behavior and reproduction: In the spring, water insects carrying P. varius larvae transform into flying adults. Crickets and grasshoppers are infected when they eat dead insects containing worm larvae. Development to adult worms inside the host takes about one month. With this fast development, as many as three generations are produced in a single year.

Paragordius varius and people: P. varius worms do not infect humans.

Conservation status: P. varius worms are not considered threatened or endangered. ∎

FOR MORE INFORMATION

Books:

Thorp, J. H., and A. P. Covich, eds. Ecology and Classification of North American Freshwater Invertebrates. San Diego, CA: Academic, 1991.

Web sites:

Hanelt, Ben. "General Gordian Worm Information." University of Nebraska, Lincoln. http://bsweb.unl.edu/emb/janovy/ben/info.html (accessed on February 3, 2005).