Black Widow Spiders

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  • Topic: Latrodectus, Black widow spider, Spider bite
  • Pages : 12 (2409 words )
  • Download(s) : 262
  • Published : October 8, 1999
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Adult black widow spiders have a shiny, black, rounded, circular abdomen and

are about 1/3 inch long (about 1-1/2 inches when their legs are spread).

Adult spiders have two reddish or yellowish triangles on their bottom which

looks like an hourglass marking, and their body color is dark colored usually

black or sometimes dark brown. They are usually recognized because of their

red or red-orange hourglass design on the bottom of their abdomen. This

pattern is changeable and may look like two separated spots. In some spiders

there is no pattern on the abdomen. The immature stages of both sexes of the

widow spiders have red or red-orange or yellow spots and strips on the top

of their abdomen. Females are colored gray or pale brown. Their color gets

darker as they get older. The hourglass pattern on the underside of the

abdomen forms throughout their development. Male widow spiders are smaller

about 1/4 inch long, and they're usually not black in overall color, instead

it looks like a light brown or gray. Male widows have an hourglass pattern

too. When they are full-grown they have large knob-like shapes called

pedipalps, which start from the head. But to females they still look the

same. Newly hatched spiderlings are white or a yellowish-white, eventually

turning blackish when they get older. Adolescents of both sexes look like

the male.

Black Widow spiders build loose and uneven mesh-type webs of rough silk in

dark places usually outdoors. And build their webs near the ground

(sometimes inside of houses) but mainly they build them outside. Black

Widows can be found near the ground in dark undisturbed areas. Nest sites

are near holes made by small animals, or around construction openings and

woodpiles. Also they can be found around low shrubs which are usual sites

for widow spiders. Black widows are also found inside in dark undisturbed

areas like behind furniture or under desks and in undisturbed basement areas

and crawl spaces of homes are areas where black widow nests are. They don't

produce a web like the weaving spiders do or the funnel pattern webs that the

funnel weaver spider's make.

The female lays eggs in silken cocoon sacs about 1/2-inch in width. The sack

is a pear shaped, and is a creamy yellow, light gray, or light brown in

color. They usually lay about 300 to 400 eggs per sac and have 4 to 9 egg

sacs made during a summer. But only 1 to 12 young survive after the egg

incubation period of about 14 to 30 days because of cannibalism. Growth

requires 2 to 4 months depending on availability of prey during which the

females shed 6 to 8 times and the males 3 to 6 times. Females mature 92 days

after the egg sac outburst and live for about 179 days, while males mature 71

days after outburst and live for 30 days. Because usually the female eats

the male after they mate. But sometimes if females are well fed, the males

get away to mate for another day. The females hang belly upward and very

rarely leave the web. In cold weather and droughts it can cause these

spiders to go into buildings. Prey caught in the web include a many

different insects (cockroaches, flys, and beetles) and other arthropods. The

female black widow is shy and usually only goes out at night. But when she

leaves her web she usually goes far away from her the web. Outbreaks of

black widows occur off and on. Some years an area may have thousands of

widows and the next year they may be gone. Certain kinds of habitats such as

sand dune areas may have black widows every year. Alternating warm and cold

weather during the winter and spring months are harmful to their survival.

The venom of the black widow spider is 15 times as toxic as the venom of the

prairie rattlesnake. However, only a small amount of the toxin is...
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