Widow spider

Taxobox
name = Widow spiders


image_width = 211px
image_caption = Black Widow spider
regnum = Animalia
phylum = Arthropoda
classis = Arachnida
ordo = Araneae
familia = Theridiidae
genus = "Latrodectus"
genus_authority = Walckenaer, 1805
subdivision_ranks = Species
subdivision = Approx. 31, see article

The widow spiders are members of the genus "Latrodectus", in the family Theridiidae. "Latrodectus" includes approximately 31 recognized venomous species, with the southern black widow spider ("Latrodectus mactans") being the best known member of the group. The female black widow's venom is particularly harmful 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", 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, or in cases where a female is protecting an egg sac, but ordinarily intrusion by any large creature will cause these spiders to flee.

This genus of spiders received their name because widow females frequently consume the males after mating, leaving them widowed. However, contrary to popular belief males that escape being consumed by the females can go on to fertilize more females [cite journal|author= Breene, R . G . and M. H. Sweet|date=1985|title=Evidence of insemination of multiple females by the male black widow spider, Latrodectus mactans (Araneae, Theridiidae)| journal=The Journal of Arachnology| volume=13|issue=3|pages=331–335 [http://www.americanarachnology.org/JoA_free/JoA_v13_n3/JoA_v13_p331.pdf PDF] ] .

pecies

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. Spiders which are found in multiple geographies are listed in their predominant native habitat.

North American widow spiders

The following widow spiders are indigenous to North America:

*"Latrodectus bishopi", the red widow, Florida, USA
*"Latrodectus geometricus", the brown widow, from northeastern US to Texas with predominance in the southeast. Now found as far west as California.
*"Latrodectus hesperus", the Western black widow, western Canada, United States, and Mexico.
*"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.

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

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

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", Iberian Peninsula
*"Latrodectus pallidus", the "white widow" or "white steppe spider", 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".

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 karrooensis", 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.

Widows of South, East, and Southeast Asia

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

Widows of Australia and Oceania

*"Latrodectus atritus", the black katipo, found in New Zealand
*"Latrodectus hasselti", the redback 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

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.

References

*Discovery Books; 2000; Insects and Spiders; St. Remy Media Inc.; New York; 35
*Freeman, Scott; 2003; Biological Science; Prentice-Hall
*Hillyard, Paul; 1994; the Book of Spiders; Random House, Inc.; New York; 47-50
*Hillyard, Paul; 1994b; The Book of the Spider; Avon Books; New York; 22-25
*Martin, Louise; 1988; Black Widow Spiders; Rourke Enterprises, Inc.; 18-20
*Preston-Malfham, Ken; 1998; Spiders; Chartwell Books; Edison; New Jersey; 40.
*"Arthropod," Microsoft Encarta Online Encyclopedia 2004
* Abalos, J.W. (1962). The Egg-sac in the Identification of Species of "Latrodectus" (Black-Widow Spiders). "Psyche" 69:268-270. [http://psyche2.entclub.org/articles/69/69-268.pdf PDF]
* Levi, H.W. & McCrone, J.D. (1964). North American Widow Spiders of the "Latrodectus curacaviensis" Group (Araneae, Theridiidae. "Psyche" 71:12-27). [http://psyche2.entclub.org/articles/71/71-012.pdf PDF]

External links

* [http://tolweb.org/Latrodectus/93274 Tree of Life: Latrodectus ]
* [http://www.cirrusimage.com/spider_black_widow.htm Black Widow Spider: Large format photographs and information]