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Webspinners, Order Embiidina

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The order Embiidina (sometimes called Embioptera) is one of the smaller insect orders. The name is derived from the Greek embio, meaning lively, an apt description of these fast running insects.

Description:

Webspinners, or footspinners, possess silk glands on their enlarged front feet, and are the only insects known to produce silk in this way. They spin elaborate silken galleries and nests in leaf litter, bark crevices, and even in epiphytic plants. They live gregariously within these nests, and feed on all manner of organic material, from moss and lichens to bark and fallen leaves.

Male webspinners are almost always winged, with slightly flattened bodies. Females, in contrast, have cylindrical bodies and never have wings. The abdomen of a webspinner has 10 segments, with a pair of cerci at the end. Members of the order Embiidina have chewing mouthparts, filiform antennae, and no ocelli. The tarsi have 3 segments.

Webspinners undergo simple metamorphosis. The female usually disguises the oval eggs, either using masticated organic matter or fecal pellets, and deposits them in an area of the silken galleries. Female webspinners provide maternal care for their offspring, guarding them as eggs and young nymphs. Even first instar nymphs possess functional silk glands.

Webspinners exhibit some interesting defensive behaviors. When threatened by a predator, many will feign death, hoping to dissuade the predator from eating them. If that doesn't work, a webspinner can quickly flee the scene – backwards. Their hind legs bear an enlarged femoral muscle that allows them to run in reverse at high speeds.

Habitat and Distribution:

Webspinners live mostly in the tropics. The 11 species known to inhabit the U.S. reside in southern states. Worldwide, there are an estimated 200 species assigned to the order Embiidina.

Families in the Order:

  • Anisembiidae
  • Teratembiidae – also called Oligembiidae
  • Oligotomidae
  • Australembiidae – males are wingless
  • Clothodidae
  • Embiidae
  • Embonychidae
  • Notoligotomidae

Families and Genera of Interest:

  • Oligotomoma males will often fly to lights on summer nights.
  • Haploembia solieri reproduces parthenogenetically, that is, without fertilization of the eggs.
  • Anisembia texana males are winged in cold, arid habitats, but wingless in humid environments.

Sources:

  • Borror and DeLong's Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson
  • Embioptera, John R. Meyer, North Carolina State University, accessed December 22, 2011
  • The Web Spinners (Embioptera), Gordon Ramel, accessed December 22, 2011
  • Order Embiidina, Bugguide, accessed December 22, 2011

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