Embioptera - The Web Spinners
Web spinners, or embiids, are a primitive group of insects. Although the earliest fossil specimen dates from the Permian period, they probably evolved earlier, in the Carboniferous period. They are about 5-12mm (0.2-0. 5") and live gregariously, hidden in silken tunnels networked to form a colony. Perhaps related to the Orthoptera, the Embioptera have a number of adaptations not found in any other insects which hinder the establishment of phylogenetic relationships. The mouthparts are directed forward rather than downward, quite unlike other primitive Orthopterans. This may be an adaptation to life in a tunnel or may mean that Embioptera are actually related to earwigs (Demaptera). Most striking of all are the tarsi of the front legs. These are enlarged and contain glands that produce silk. No other group of insects, fossil or modern, have silk-producing glands in the legs. This silk is used to construct elaborate nests and tunnels under leaves or bark. Web spinners live within these silken nests, feeding on all manner of vegetable matter. They rarely leave their network of tunnels, the colony growing through incorporation of new food sources. The ordinal name Embioptera is derived from the Greek words “embio” (lively) and “ptera” (wing). The name references the fluttery movement of wings observed in male Embioptera. Only adult males have these wings, of which there are two pairs. Front and hind wings are similar in shape and unusually flexible and can fold forward over the head when the insect runs backward through its tunnels. Hemolymph is pumped into anterior veins to stiffen the wings during flight. Male web spinners only live for a short time and those species with wings fly around in search of females (who sometimes eat their suitors). After mating, female web spinners either lay their eggs in an established gallery or disperse to begin a new colony. The female protects her eggs and, in some species, feeds the nymphs upon hatching. The nymphs resemble the adults and live together with their extended family, spinning silken galleries of their own. Females of different species are so similar in appearance that it is often impossible to tell them apart. Male web spinners may sometimes be attracted to lights at night. Most Embioptera are tropical or subtropical. There are 200+ species.