Thursday, March 12, 2009

Spider


The Spider's Silk: As part of the arachnid class spiders have two main body segments: the cephalothorax and abdomen. Their ability to produce silk separates spiders from other arachnids. The silk is used to capture prey in elaborately woven webs, to wrap and protect eggs, and as a bungee-like cord to move from place to place.
Toxin Toolkit: Almost all spiders have venom-injecting fangs, which they use to kill their prey. Some spiders inject a neurotoxin, which affects the victim's nervous system, typically resulting in paralysis. Others inject a cytotoxin, which damages the victim's cellular tissue.
An Extra Set of Hands: Two leglike pedipalps located near the spider's head are used in a variety of ways. One of the most important is bringing food to the mouth. In adult males, the ends of the pedipalps are modified and used for the transfer of sperm during mating. Spiders also use their pedipalps for sensing their environment; sensitive hairs pick up vibrations, air currents and even scent.
Spiders, Spiders Everywhere: At least 40,000 species of spider have been described by science, but this number only accounts for one-third to one-fifth of all spider species on earth. Spiders can be found in just about every terrestrial habitat and some water ones as well, from tropical rain forests, woodlands, caves and gardens to your home.
Sacrificial Males: A female spider will often kill the male shortly after mating. By feeding the female, who will ultimately lay and tend the resulting fertilized eggs, the male ensures that his genes will carry on. In lieu of self-sacrifice, some male spiders will offer a fly or other meal to the female before mating.

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