[3] Bootlace worms may grow very long but are usually only 5 to 10 millimetres (0.20 to 0.39 in) in width.

[5] When handled, it produces large amounts of thick mucus with a faint pungent smell, reminiscent of iron or sewage.

[6] This toxic mucus has been shown to kill crabs and cockroaches, and could have applications as an agricultural insecticide.

[7] In 1864, William M'Intosh described a specimen that had washed ashore in the aftermath of a severe storm by St Andrews, Scotland, which was more than 55 m (180 ft) long,[8] longer than the longest known lion's mane jellyfish, the animal which is often considered to be the longest in the world.

Instead, it has a cluster of sticky filaments at the end of its proboscis that it uses to immobilize prey.