The Velvet Worms (phylum Onychophora)
by Leo Shapiro
The phylum Onychophora includes around 110 described species (and likely a similar number undescribed) of caterpillar-like relatives of arthropods (disputed), found in the trpical and subtropical regions of the world, as well as the temperate regions of Australia and New Zealand. The first description of a living onychophoran was in 1826 (misinterpreted as a leg-bearing “slug”, a mollusc).
All living species are terrestrial, but a number of marine species are known from the fossil record going back to the Early Cambrian over 500 million years ago. Living Onychophora are found in humid habitats, stashing themselves away in burrows or other retreats and becoming inactive during dry periods. During wet periods, they can be found sifting through leaf litter.
One particularly unusual aspect of onychophoran behavior is their method of prey capture, which involves shooting twin streams of a rapidly hardening adhesive slime up to 30 cm to entangle their prey, as can be seen here. (Brusca and Brusca 2003) With the exception of just a few species, onychophorans have not been well studied and the New World fauna is especially poorly known (Read 1988)…
(read more: Encyclopedia of Life)
images: Andras Keszei; urosphena; Bruno Vellutini; Stanley Kemp and Sonia Martinez; and Geoff Gallice