Spiders are invertebrate animals classified within one of the major subdivisions of the family Arthropoda, which includes horseshoe crabs and related forms. They have outlasted the now extinct trilobites, a common marine arthropod of the Cambrian era.
Spiders occur in a large range of sizes. The smallest, dwarf spiders of the subfamily Erigoninae, are less than 1 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have leg spans up to 10 inches).
Many spiders may only live for about a year, but a number will live two years or more, overwintering in sheltered areas. It is common for female tarantulas to live up to twenty years. The annual influx of outdoor spiders into houses in the fall is due to this search for a warm place to spend the winter.
Arachnophobia is an abnormal fear of spiders. It is among the most common of phobias in certain regions of the world. The reactions of arachnophobics often seem irrational. People with arachnophobia tend to feel uneasy in any area they believe could harbor spiders or that has visible signs of their presence, such as webs. If they see a spider they may not enter the general vicinity until they overcome the panic attack that is often associated with their phobia. The fear of spiders can be treated by any of general techniques suggested for specific phobias.
Although spiders are feared and disliked by many, they benefit humankind by destroying many insects pests such as fly, mosquitoes, grasshoppers, locusts, cockroaches, and aphids. Spiders have many medical uses such as using their venom to treat arthritis.
Spiders, especially larger ones, are eaten routinely or as a delicacy in various parts of the world, including Cambodia, where fried spider is considered a delicacy. In Thailand, the Solomon Islands, and parts of South America, living wrapped tarantulas are sometimes taken on trips by certain indigenous tribes.
Spider webs in space were spun in 1973 aboard Skylab, involving two female European garden spiders called Arabella and Anita. The aim of the experiment was to test whether the two spiders would spin webs in space. The experiment was a student project of Judy Miles of Lexington, Massachusetts.
The spiders were released into a box that resembled a window frame. They proceeded to construct their webs, although they took a long time to adapt to their weightless existence. The crew members fed and watered the spiders, giving them filet mignon.
When scientists studied the webs, they discovered that the space webs were finer than normal Earth webs, and there was a definite difference in the characteristics of the webs. Additionally, while the webs were finer overall, the space web had variations in thickness in places. Some spots were slightly thinner, and others slightly thicker.
Anita died in orbit. Arabella was found dead on return to earth. Both were found to have lost considerable weight and were probably dehydrated. The remains of Anita, along with the web frame, can be seen at the Smithsonian Air and Space Museum.
Spiders have been attributed by numerous cultures with the origination of basket weaving, knotwork, weaving, spinning and net making. Spiders are pervasive throughout folklore and mythology. Spinning and binding is evident in the etymologies of the terms religion, yoga and tantra.
The Moche people of ancient Peru worshipped nature. They placed emphasis on animals and often depicted spiders in their art.