Peripatus today have tracheae (tubes for breathing), but cannot close them as the tubes lack spiracles or valves. This means they lose moisture readily and need to live in damp microclimates to avoid dehydration. However, they can drown in pooling water.
Typically velvet worms live in damp forest, under or inside rotting logs, or in the undergrowth. They have also recently been found in tussock grassland. One egg-laying species (currently unnamed) has been discovered under rocks alongside the Tasman Glacier. Velvet worms are often found in decaying logs on farmland without tree cover.
Research in Australia found that males colonise new logs and secrete a pheromone (chemical signal) which attracts females and other males. It also found that females were much more common than males. The researchers concluded that by seeking out new logs, male velvet worms were put at risk, but reproductive females were spared having to spend time searching for new food and shelter.
New Zealand velvet worms are relatively slow moving – taking about a minute to cover a distance of 20 centimetres. Some overseas species are faster, and can trundle along at up to 60 centimetres a minute.
Velvet worms are active predators, eating invertebrates such as isopods (small crustaceans), spiders, cockroaches, wētā and beetles. Nocturnal and virtually sightless, they recognise prey using their sensitive antennae, and squirt it with a gooey fluid from glands called oral papillae on each side of the head. The twin streams trap the victim in glue. The velvet worm then tears the creature open with its jaws and injects saliva, which contains digestive enzymes. It can then suck out the partially digested innards at its leisure.
New Zealand peripatus can accurately hit prey at a range of several centimetres. They may spit further than this when defending themselves from predators. Some overseas species can spit up to 50 centimetres.