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ARACHNIDS
The spider and its relatives, the scorpions, mites and ticks, keep the old name Arachnida, an order whose members range in size from a microscopic mite to a tarantula, whose body is five inches long and whose legs span eight inches. Arachnids, like their six legged cousins the insects, are
arthropods. The evolutionary descendants of sea-dwelling creatures called trilobites. The first known land animal was a scorpion; it appeared some 400 million years ago. In the time since, arachnids have evolved into no fewer than 54,590 species. They flourish virtually every place on earth that can support life. They live in the scorching deserts, chilly mountain tops, and some even spend their lives in water.
For all the widespread fear and revulsion they provoke, and despite the fact that almost all are venomous, few spiders are capable of causing man any serious or lasting harm. Of the 35,000 known species of spider, only about 500 can drive their poison into human skin. Once the poison has been injected, however, it can have a rapid, although rarely fatal effect.
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