spider (redirected from Arachnea)

spider, organism, mostly terrestrial, of the class Arachnida, order Araneae, with four pairs of legs and a two-part body consisting of a cephalothorax, or prosoma, and an unsegmented abdomen, or opisthosoma. The cephalothorax is covered by a shield, or carapace, and bears eight simple eyes. On the underside of the head (the cephalic part of the cephalothorax) are two pairs of appendages, the anterior pair called chelicerae and the second pair pedipalps, with which the spider captures and paralyzes its prey, injecting into it venom produced in the poison glands. The spider then liquefies the tissues of the prey with a digestive fluid and sucks this broth into its stomach where it may be stored in a digestive gland. Breathing is by means of tracheae (air tubes) or book lungs, or both. Arachnid book lungs are similar to the gill books of horseshoe crabs but are internal and adapted to a terrestrial habitat. Three pairs of spinnerets toward the tip of the abdomen produce protein-containing fluids that harden as they are drawn out to form silk threads. Several kinds of silk glands and spinnerets produce different kinds of silk used variously for constructing cocoons or egg sacs, spinning webs, and binding prey; other light strands are spun out for ballooning, or floating, the spiders, especially young ones, long distances on air currents. Spider silk is used for the cross hairs in certain optical instruments. Spiders live chiefly on insects and other arthropods; some large spiders ensnare and kill small snakes, birds, and mammals. Many are cannibalistic; the female may eat the male when courtship and mating are completed. Young, growing spiders can regenerate missing legs and parts of legs. Several species of spiders have bites that are exceptionally painful, or even dangerous to humans. Species of black widow spiders, which are found in the warmer parts of the world including the United States and S Canada, have a virulent neurotoxic venom. The bite venom of the brown recluse spider of SE and S central United States decomposes tissue, resulting in slow healing and sometimes leaving a sunken scar as large as a quarter. Among the more interesting spiders are the tarantula; its relative the trap-door spider, which ambushes its prey from a silk-lined burrow covered by a hinged lid; the orb weavers, which spin beautiful circular webs; and the crab spider, jumping spider, and wolf spider, named for their habits. Spiders are classified in the phylum Arthropoda, class Arachnida, order Araneae.

Bibliography

See B. J. Kaston, How to Know the Spiders (3d ed. 1978); R. F. Foelix, Biology of Spiders (1982); The Audubon Society Field Guide to North American Insects and Spiders (1992).

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spider

Any of approximately 38,000 predatory arachnid species, mostly terrestrial, in the order Araneida, abundant worldwide except in Antarctica. Spiders have two main body parts, eight legs, two pincerlike venomous appendages, and three pairs of spinnerets. Species range in length from 0.5 to about 90 mm (0.02 to 3.5 inches). The venom of a few species (e.g., brown recluse) is harmful to humans. Most species catch insect prey in a web of silk extruded from the spinnerets. Spiders change little during growth, except in size. Species are classified largely on the basis of the number and arrangement of eyes and the type of web. See also black widow; tarantula; wolf spider.

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spider

(1) (Spider) A gaming platform from AMD. See Phenom.

(2) Also known as a "crawler," "ant," "robot" (bot) and "intelligent agent," a spider is a program that searches for information on the Web. Spiders are widely used by Web search engines to index all the pages on a site by following the links from page to page. The search engine summarizes the content and adds the links to their indexes. Spiders are also used to locate Web pages that sell a particular product or to find blogs that have opinions about a product. See spidering program.

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spider

1. any predatory silk-producing arachnid of the order Araneae, having four pairs of legs and a rounded unsegmented body consisting of abdomen and cephalothorax

2. any of various similar or related arachnids

3. a hub fitted with radiating spokes or arms that serve to transmit power or support a load

4. any implement or tool having the shape of a spider

5. Nautical a metal frame fitted at the base of a mast to which halyards are tied when not in use

6. Brit a cluster of elastic straps fastened at a central point and used to hold a load on a car rack, motorcycle, etc.

7. Billiards Snooker a rest having long legs, used to raise the cue above the level of the height of the ball

8. Angling an artificial fly tied with a hackle and no wings, perhaps originally thought to imitate a spider

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spider [′spīd·ər]

(agriculture)

An attachment to a cultivator that pulverizes the soil.

(computer science)

A program that searches the Internet for new, publicly accessible resources and transmits its findings to a database that is accessible to search engines.

(electricity)

A structure on the shaft of an electric rotating machine that supports the core or poles of the rotor, consisting of a hub, spokes, and rim, or some similar arrangement.

(engineering)

The part of an ejector mechanism which operates ejector pins in a molding press.

In extrusion, the membranes which support a mandrel within the head-die assembly.

(engineering acoustics)

A highly flexible perforated or corrugated disk used to center the voice coil of a dynamic loudspeaker with respect to the pole piece without appreciably hindering in-and-out motion of the voice coil and its attached diaphragm.

(invertebrate zoology)

The common name for arachnids comprising the order Araneida.

(mechanical engineering)

In a universal joint, a part with four projections that is pivoted between the forked ends of two shafts and transmits motion between the shafts. Also known as cross.

(metallurgy)

In founding, a device that consists of a frame with radiating arms or members and is used for strengthening a core or mold.

(petroleum engineering)

A steel block with a tapered opening which permits passage of pipe during movement into or from a well; designed to hold pipe suspended in the well when the slips are placed in the tapered opening and in contact with the pipe.

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(World-Wide Web)

spider - (Or "robot", "crawler") A program that automatically explores the World-Wide Web by retrieving a document and recursively retrieving some or all the documents that are referenced in it. This is in contrast with a normal web browser operated by a human that doesn't automatically follow links other than inline images and URL redirection. The algorithm used to pick which references to follow strongly depends on the program's purpose. Index-building spiders usually retrieve a significant proportion of the references. The other extreme is spiders that try to validate the references in a set of documents; these usually do not retrieve any of the links apart from redirections. The standard for robot exclusion is designed to avoid some problems with spiders. Early examples were Lycos and WebCrawler. http://info.webcrawler.com/mak/projects/robots/robots.html.