Black Widow Spider

 Tuesday Topics – Natural History

Turning over rocks, boards, or anything lying on the ground anywhere in the temperate areas of the United States can be hazardous. Black Widow spiders prefer cool, protected areas under almost anything on or near the ground. This habitat provides a protected area for a web and a ready source of prey. This is one reason gloves are recommended when working outside, especially picking up anything off of, or near the ground.

The Spider

The Black Widow belongs to a large family of “widow” spiders. There are three species of North American Black Widows, all similar in appearance. All are usually black in color with distinctive red markings on the underside of the abdomen, typically in the shape of an hour glass. Individuals may differ, having a pair of red spots—sort of a poorly developed hour-glass shape. Northern Black Widows may have white stripes on their bodies and red bands on their legs.

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A common Black Widow spider with the red hourglass clearly visible. This one was living under a piece of cardboard that was lying on a coil of garden hose. She was discovered as I was in the process of retrieving the hose.

The black body is roughly the size of a large pea, a head, all supported on eight narrow jointed legs.

The Name

“Widow” spiders get their name because shortly after mating, the female kills and eats the male, although this may not always occur in nature. This behavior is based on observations of captive pairs in laboratories where the male did not have a chance to escape.

Habits

The Black Widow spins an irregular web of sticky fibers, usually from beneath a sheltering stone, wood, or other material. The spider suspends herself above the center web and waits for a victim. Once an insect is trapped in the web, the spider bites the prey, immobilizing it with its venom. She uses her two hind legs to wrap the web around the insect. These legs have comb-like bristles specially adapted for this task. Using her fangs, she injects an enzyme into the insect that liquefies the internal organs of the insect. This is her meal.

The female lays 200 to 900 eggs. The young hatch out as fully formed, but tiny spiders. They are cannibalistic, and few of the spiders survive to be adults.

The Venom

The initial physical sensation of a Black Widow bite is similar to small needle puncture. Even then, venom may not be injected into the wound, and there may be no further sensation. If venom is injected, the venom acts on nerves causing the massive release of the neurotransmitters that results in severe pain, cramps, sweating and a rapid pulse. However, despite the notoriety, Black Widow bites are rarely fatal. Those at most risk are small children, the elderly, and to those already weakened by some other illness. Only female bites are dangerous to humans.

For those that need to know:

The taxonomy of the Black Widow:

  • Kingdom: Animalia
  • Phylum:Arthropoda
  • Subphylum:Chelicerata
  • Class:Arachnida
  • Order:Araneae
  • Family:Theridiidae
  • GenusLatrodectus
  • Species worldwide: 31 species of “widow spiders,” including: Latrodectus hersperus (western black widow), Latrodectus mactans (southern black widow) and Latrodectus variolus (northern black widow)

Photography and Text Copyrighted 2016 – Jeff Richmond

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