Spider Silk and Venom
Spiders are arthropods of the class arachnida along with ticks, mites and scorpions. Of the arachnids, they are in the order Araneae which contains about 40,000 known species found worldwide except in Antarctica. In the UK, there are more than 630 species including the garden spider, Araneus diadematus, which is reknowned for spinning beautiful webs. There are three housespider species: Tegenaria domestica, Tegenaria atrica and Tegenaria parietina (the cardinal spider).
Spiders have 8 legs, 8 simple eyes (4 pairs) and fangs with which they bite their prey. Most are less than 1 cm in length but the largest spider is the bird-eating spider from South America with a body length of 9 cm. Males are often much smaller than the females of the same species.
The general lifespan is about 1 year but males often die after mating and females after egg-laying. The eggs are encased in a silken sac woven by the female and after hatching, the young spiders molt until they reach adult size.
Spiders are generally not social and are mostly terrestrial although some species are aquatic, such as Argyroneta aquatica. Aquatic spiders breathe underwater by trapping air bubbles with silk and dragging the bubbles with them.
Spiders are predators and they play an important role in agricultural and domestic pest control since their main source of food is insects. Interest in how spiders can help humans has become increasingly important, especially the potential applications of natural or synthetic spider silk in the materials industry and spider venom in medicine.