Widow spider

From Free net encyclopedia

{{Taxobox | color = pink | name = Widow spiders | image = BlackWidowSpider.jpeg | image_width = 200px | image_caption = Black Widow spider | regnum = Animalia | phylum = Arthropoda | classis = Arachnida | ordo = Araneae | familia = Theridiidae | genus = Latrodectus | subdivision_ranks = Species | subdivision = Approx. 31, see article }}

The widow spiders are members of the spider genus Latrodectus, in the family Theridiidae. Latrodectus includes approximately 31 recognized venomous species, with the black widow spider (Latrodectus mactans) being the best known member of the group. The female black widow's venom is particularly poisonous to humans (males almost never bite humans). Spiders of the genus Steatoda (also of the Theridiidae family) are often mistaken for widow spiders, and are known as false widow spiders. The false widow spiders are significantly less harmful to humans. (For comparisons with other particularly venomous spiders, see Spiders_having_medically_significant_venom.)

Along with the Latrodectus mactans, the glossy black ones with the famed red hourglass, the gray or brown widow spiders (Latrodectus geometricus), the red widow spiders (Latrodectus bishopi), the northern widows (Latrodectus variolus), and the western widows (Latrodectus hesperus) (Preston-Malfham, 1998) are also found in the United States. But there are widow spiders on every continent of the world except for Antarctica. In some areas in Africa this Genus receives the generic name button spiders.

In common with other members of the Theridiidae family, the widow spiders construct a cobweb, i.e., an irregular tangle of sticky silken fibers. The black widow spider very frequently hangs upside down near the center of its web and waits there for insects to blunder in and get stuck. Then, before the insect can extricate itself, the spider rushes over to bite it and swathe it in a silken shroud. If the spider feels threatened it will normally let itself down to the ground on a safety line of silk just as fast as it can. As with other web-weavers, these spiders have very poor eyesight and depend mostly on vibrations reaching them through their webs to orient themselves to prey or warn them of larger animals that could injure or kill them. They are not aggressive, and most injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched somehow. It is possible that some bites may result when a spider mistakes a finger thrust into its web for its normal prey, but ordinarily intrusion by any large creature will cause these spiders to flee.

Image:Latrodectus map.gif Range of Latrodectus species worldwide

1 Species
2 References
3 External links

[edit]

Species

The silk of the Latrodectus genus is larger in diameter than the silk of other spiders, and, as with all spider silk, it is stronger than an equal-sized filament of steel. Because of these excellent characteristics it was in great demand to use in the construction of reticles for rifle sights at least as late as World War I.

The black widow spider, Latrodectus mactans, has a prominent red hourglass figure on the underside of its abdomen. Many of the other widow spiders have red patterns on a glossy black or dark background, which serve as a warning. Some of the more well known species of widow spiders are listed below, together with some of the areas where they are found. This list should not be considered complete. Spiders which are found in multiple geographies are listed in their predominant native habitat.

[edit]

North American widow spiders

The following widow spiders are indigenous to North America:

Latrodectus bishopi, the red widow, Florida, USA

Latrodectus hesperus with egg sac

Latrodectus hesperus, the Western black widow, western USA. Also found in Israel.
Latrodectus mactans, the black widow spider (sometimes called the Southern black widow), warm regions of the USA
Latrodectus variolus, the Northern black widow, from the extreme southeastern part of Canada and south to northern Florida, with frequency higher in the northern part of this range.

[edit]

Widows of central and south America

The following are indigenous to central and south America.

Latrodectus antheratus, Paraguay, Argentina
Latrodectus apicalis, Galapagos Islands
Latrodectus corallinus, Argentina
Latrodectus curacaviensis, Lesser Antilles, South America
Latrodectus diaguita, Argentina
Latrodectus mirabilis, Argentina
Latrodectus quartus, Argentina
Latrodectus variegatus, Chile and Argentina

[edit]

Widows of Europe, North Africa, the Middle East, and western Asia

Image:Latrodectus tredecimguttatus female.jpg The following widows indigenous to the Mediterranean region, as well as in western Asia.

Latrodectus dahli, Middle East to central Asia.
Latrodectus hystrix, Yemen, Socotra
Latrodectus lilianae, Spain
Latrodectus pallidus, the white widow, North Africa, the Middle East, Russia, Iran, Cape Verde.
Latrodectus revivensis, Israel.
Latrodectus tredecimguttatus, the Mediterranean Black Widow (or European Black Widow), Mediterranean area, central Asia, Kazakhstan. Also reported in China. Some specimens are reported as L. lugubris.

[edit]

Widows of sub-Saharan Africa and Madagascar

Latrodectus cinctus, one of the black button spiders, southern Africa. Also found in Cape Verde and Kuwait.
Latrodectus indistinctus, one of the black button spiders, South Africa and Namibia
Latrodectus karooensis, another of the black button spiders, S. Africa
Latrodectus menavodi, Madagascar
Latrodectus obscurior, Cape Verde, Madagascar
Latrodectus renivulvatus, one of the black button spiders, Africa. Also in Saudi Arabia and Yemen.
Latrodectus rhodesiensis, one of the brown button spiders, Zimbabwe.

[edit]

Widows of South, East, and Southeast Asia

Latrodectus elegans, China, Myanmar, Japan
Latrodectus erythromelas, Sri Lanka

[edit]

Widows of Australia and Oceania

Latrodectus atritus, the black katipo, found in New Zealand
Latrodectus hasselti, the red-back spider, native to Australia. Also found in Southeast Asia and New Zealand, imported into both regions.
Latrodectus katipo, the red katipo, found in New Zealand

[edit]

Widows found worldwide

Latrodectus geometricus, the brown widow, grey widow, or brown button spider, Africa, USA, S. America, Australia. It is unclear where this spider originated; however it has been discovered in many warm, cosmopolitan locales.

[edit]