Silk is produced by a variety of animals, for different purposes, with various types being produced.
Insects Silkworms produce silk when undergoing larval to adult metamorphosis. Raspy crickets produce silk to form nests. Honeybee and bumblebee larvae produce silk to strengthen the wax cells in which they pupate. Bulldog ants spin cocoons to protect themselves during pupation. Weaver ants use silk to connect leaves together to make communal nests. Caddisfly larvae produce silk. Webspinners have silk glands on their front legs. Hornets Silverfish Mayflies Thrips Leafhoppers produce silk nests under the leaves of the trees where they live, to protect them against predators. Beetles Lacewings Fleas Flies Midges Caterpillars of many butterfly species use silk to create shelters or attach to substrates for pupation. Parasitic wasps such as braconids use silk cocoons for pupation.
Other animals The family Projapygidae in the order Diplura have cerci that contain silk glands. The mussel Pinna nobilis creates silk to bond itself to rocks. It is used to make sea silk. Spiders make spider silk for various purposes such as weaving their webs, protecting their eggs or as a safety line. The amphipod Peramphithoe femorata uses silk to make a nest out of kelp blades. Another amphipod, Crassicorophium bonellii, use silk to build shelter. Carp produce fibroin units, a component of silk, to attach their eggs to rocks. Spider mites make webs that protects them against predators. Symphyla produce silk through a pair of spinnerets, which is used for nest building, escape and defense. Pseudoscorpions make silk chambers in which they molt. Goats have been genetically modified to produce milk containing extractable silk proteins. Dulichia rhabdoplastis
References
External links US National Library of Medicine, National Institutes of Health, documentation about various animals that produce silk and why.