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Velvet Worms: Onychophora

Behavior And Reproduction

As with arthropods, which include insects, spiders, and their relatives, velvet worms must molt, or shed their exoskeleton, in order to grow. These secretive animals capture prey with threads of clear, sticky slime shot from the oral papillae. The slime is also used to discourage predators and can be squirted up to 1.6 feet (0.5 meters) in distance. During the dry season, or periods of low temperature, velvet worms crawl down into crevices in the soil and remain there until conditions on the surface improve.

Mating has been observed in very few species. Males produce special chemicals, or pheromones (FEH-re-moans), from glands located at the bases of their legs to attract females. In some species, males deposit sperm packets directly into the female's reproductive opening. In other species, the packets are placed on the female's body and are absorbed directly through the exoskeleton. The sperm is sometimes stored for several months before the eggs are fertilized.

Some velvet worms deposit their eggs in the soil, and the young develop and are nourished inside the egg until they hatch later. Others also produce eggs, but they hatch inside the female's body and young are born live. A few species give live birth to young that are nourished by the mother's body until they are born, headfirst. Whether born or hatched, all young velvet worms resemble small adults.


Velvet worms have changed very little since their marine ancestors first came on land about 400 million years ago. Discovered in 1826, velvet worms were first thought to be a kind of slug. Later scientists realized that they shared features of both segmented worms (Annelida) and arthropods, and they were placed in their own phylum. They have been called the "missing link" that connects these two groups, but recent studies show that they are more closely related to arthropods than annelids.

Additional topics

Animal Life ResourceMollusks, Crustaceans, and Related SpeciesVelvet Worms: Onychophora - Physical Characteristics, Behavior And Reproduction, Conservation Status, No Common Name (epiperipatus Biolleyi): Species Account - GEOGRAPHIC RANGE, HABITAT, DIET, VELVET WORMS AND PEOPLE