Orb-weaver spider
<p>The <b>orb-weaver spiders</b> (family <i>Araneidae</i>) are the builders of spiral wheel-shaped webs often found in gardens, fields and forests. The family is a large one, including over 2800 <a title="Species" href="http://en.wikipedia.org/wiki/Species">species</a> in over 160 <a title="Genus" href="http://en.wikipedia.org/wiki/Genus">genera</a> worldwide, making it the third largest family of <a title="Spider" href="http://en.wikipedia.org/wiki/Spider">spiders</a> known (behind <i><a title="Salticidae" href="http://en.wikipedia.org/wiki/Salticidae">Salticidae</a></i> and <i><a title="Linyphiidae" href="http://en.wikipedia.org/wiki/Linyphiidae">Linyphiidae</a></i>). The oldest known orb-weaving spider is <i><a title="Mesozygiella dunlopi" href="http://en.wikipedia.org/wiki/Mesozygiella_dunlopi">Mesozygiella dunlopi</a></i>, with specimens in <a title="Amber" href="http://en.wikipedia.org/wiki/Amber">amber</a> dating from the <a title="Early Cretaceous" href="http://en.wikipedia.org/wiki/Early_Cretaceous">Early Cretaceous</a>.</p><p>Generally, orb-weaving spiders are three-clawed builders of flat <a title="Spider web" href="http://en.wikipedia.org/wiki/Spider_web">webs</a> with sticky spiral capture <a title="Spider silk" href="http://en.wikipedia.org/wiki/Spider_silk">silk</a>. The building of a web is an engineering feat, begun when the spider floats a line on the wind to another surface. The spider secures the line and then drops another line from the center, making a "Y". The rest of the scaffolding follows with many radii of non-sticky silk being constructed before a final spiral of sticky capture silk. The third claw is used to walk on the non-sticky part of the web. Characteristically, the prey <a title="Insect" href="http://en.wikipedia.org/wiki/Insect">insect</a> that blunders into the sticky lines is stunned by a quick bite and then wrapped in silk. If the prey is a <a title="Venom (poison)" href="http://en.wikipedia.org/wiki/Venom_(poison)">venomous</a> insect, such as a wasp, wrapping may precede biting.</p><div class="thumb tleft"> </div><p>Some "orb-weavers" do not build webs at all. Members of the genera <i>Mastophora</i> in the Americas, <i>Cladomelea</i> in Africa and <i>Ordgarius</i> in <a title="Australia" href="http://en.wikipedia.org/wiki/Australia">Australia</a> produce sticky globules, which contain a <a title="Pheromone" href="http://en.wikipedia.org/wiki/Pheromone">pheromone</a> analog. The globule is hung from a silken thread dangled by the spider from its front legs. The pheromone analog attracts male moths of only a few species. These get stuck on the globule and are reeled in to be eaten. Interestingly, both types of <a title="Bolas spiders" href="http://en.wikipedia.org/wiki/Bolas_spiders">bolas spiders</a> are highly camouflaged and difficult to locate.</p><p>The spiny orb-weaving spiders in the genera <i>Gasteracantha</i> and <i>Micrathena</i> look like plant seeds or thorns hanging in their orb-webs. Some species of <i>Gasteracantha</i> have very long horn-like spines protruding from their abdomens.</p><p>One feature of the webs of some orb-weavers is the <a title="Web decorations" href="http://en.wikipedia.org/wiki/Web_decorations">stabilimentum</a>, a crisscross band of silk through the center of the web. It is found in a number of genera, but <i><a title="Argiope (spider)" href="http://en.wikipedia.org/wiki/Argiope_(spider)">Argiope</a></i>, which includes the common garden spider of Europe as well as the yellow and banded garden spiders of North America, is a prime example. The band has been hypothesized to be a lure for prey, a marker to warn birds away from the web and a <a title="Camouflage" href="http://en.wikipedia.org/wiki/Camouflage">camouflage</a> for the spider when it sits in the center of the web.</p><p>Most arachnid webs are vertical and the spiders usually hang with their head downward. A few webs, such as those of orb-weaver in the genus <i>Metepiera</i> have the orb hidden within a tangled space of web. Some <i>Metepiera</i> are semi-social and live in communal webs. In Mexico such communal webs have been cut out of trees or bushes and used for living fly paper.</p>[attach]6066[/attach]<br/>
