Greek: nematos = thread, morphe = form
About 250 Nematomorpha species have
been described so far. Their common name comes from the superstition that the worms are born from horse hair falling into water.
They range in size from 10 cm to over 100 cm in length,
but are always less than 3 mm in diameter, and are parasites of insects (often
beetles or grasshoppers) and other arthropods. They are found world wide.
Locomotion is achieved by the
same method as the Nematoda. The main difference
between Nematomorpha adults and Nematoda adults is the degenerate gut in the
The role of the adults is not feeding, but reproduction and
dispersal, and they have a featureless body, as the name, hair worm, suggests.
They are free living, usually in freshwater or damp soil where the smaller male
swims or wriggles towards the relatively inactive, larger female to mate.
main feeding is done in the juvenile and larval stages (the drawing on the right shows the larval stage). These resemble
the adult Kinorhynchans, some species of Priapidula, and Loriciferans. The larvae are equipped with
eversible stylets that may be used in penetrating the host's
The female lays her eggs in long strings in water. If the host is a terrestrial insect it is stimulated by some unknown mechanism to find water when the parasitic larval hairworm is ready to emerge as an adult.