Velvet worms pose virtually no threat to humans. These ancient, terrestrial invertebrates, belonging to the phylum Onychophora, are specialized ambush predators. They are secretive animals that prefer to avoid large disturbances, which means human encounters are rare and usually accidental. The velvet worm’s unique hunting mechanism is highly effective against small prey but presents no danger to people.
What Exactly Is a Velvet Worm?
Velvet worms are considered “living fossils” because their body plan has remained largely unchanged for over 500 million years. They are soft-bodied invertebrates that look somewhat like caterpillars, featuring a velvety skin texture due to numerous tiny, overlapping papillae. Most species are between two and ten centimeters long, though some can reach up to 22 centimeters. They possess multiple pairs of stubby, unjointed legs, each ending in a pair of tiny claws, which gives them their scientific name, Onychophora, meaning “claw-bearers.”
Velvet worms are strictly terrestrial, found in tropical and temperate regions of the Southern Hemisphere, including Australia, New Zealand, and Central and South America. Because they cannot effectively regulate water loss through their skin, they live exclusively in dark, moist microhabitats. These environments include rotting logs, leaf litter, and under stones, where humidity levels remain consistently high. They are nocturnal and actively hide from light, which limits the chances of human interaction.
The Mechanism of Attack
The velvet worm captures prey using a quick-hardening adhesive slime. This slime is launched from a pair of specialized structures on the head called oral papillae, which are modified limbs positioned near the mouth. The animal contracts muscles around a reservoir to eject the milky-white, glue-like substance in twin jets. The papillae oscillate rapidly as the fluid exits, causing the slime to spray in an erratic, wide-ranging pattern.
This split-second spray is highly effective for ensnaring small invertebrates like spiders, insects, and woodlice, often covering and immobilizing them in a sticky net. The slime is composed mostly of water, complex proteins, and detergent-like molecules. Upon hitting the air, the water rapidly evaporates, causing the proteins to aggregate and the substance to solidify almost instantly into a tough, restraining material. Once the prey is trapped, the velvet worm uses its jaws to create an opening and injects digestive enzymes before consuming the liquefied contents.
Risk Assessment for Humans
While the sight of a creature spraying a sticky substance may appear menacing, the velvet worm poses no danger to humans. The adhesive slime is a non-venomous, non-toxic protein mixture designed only to subdue small invertebrate prey. If a person were to be sprayed, the sticky material would adhere to the skin or clothing without causing any harmful physical or chemical reaction.
Encounters are uncommon because velvet worms are small, slow-moving, and avoid light and dry conditions. Their primary defense against a large creature like a human is to retreat or curl up, not to attack. If contact with the slime were to occur, it is easily washed away with water, though the hardened residue may require some gentle scrubbing.