Black Widow Spiders
Latrodectus hesperus

Black Widow Spider: Overview | Spider Bites | Prevention

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Description/Identification

• Females are about .5 inches long, 1.5 inches when the legs are spread.
  
  
• Females and males have a shiny, globular abdomen
  
  
• Females and males are black and sometimes brown
  
  
• Females usually have a reddish hourglass shape on the underside of her abdomen. Some species have a series of red spots and two crosswise bars on the underbelly.
  
  
• Males about half the female's size, with smaller bodies, and longer legs
  
  
• Males usually have yellow and red bands and spots over the back as do the immature stages.
  
  
• Newly hatched spiderlings are predominately white or yellowish-white, gradually acquiring more black and varying amounts of red and white with each molt.
  
  
• Juveniles of both sexes resemble the male and are harmless to humans.
  

Geography – Range

Black Widow spiders inhabit most of the warmer regions of the world to a latitude of about 45 degrees N. and S. They occur throughout all four deserts of the American Southwest.

Comparisons

The Brown Widow Spider (Latrodectus geometricus) is not as dangerous as some other widow spiders because the Brown Widow Spider is less likely to bite someone, and injects less poison. Still, it is a venomous creature, and must be treated with respect. It is found throughout the world's tropical regions, and has been introduced into southern Texas and central and southern Florida.

Hundreds of Australians are bitten every year by the Red-back Spider (Latrodectus hasselti) a close relative of the Black Widow Spider. The Red-back is found in all parts of

Australia except in the hottest deserts and on the coldest mountains.

Behavior

Both Western and Eastern Black Widows spin webs that lack shape and form. Their webs are erratic in appearance, and the silk is stronger than almost all other arachnids. The webs are rough and sticky. The black widow spider is shy and nocturnal in habit, usually staying hidden in her web, hanging belly upward. Although not aggressive, she may rush out and bite when her web is disturbed or when accidentally

Habitat

On the underside of ledges, rocks, plants and debris, wherever a web can be strung. Cold weather and drought may drive these spiders into buildings.

Food & Hunting

Like most arachnids, the Black Widow preys on insects. Prey caught in the web include a variety of insects (cockroaches and beetles) and other arthropods. After ensnaring its prey in the web, the Black Widow makes small punctures in the victim's body and sucks out the liquid contents. The Black Widow is preyed upon by Mud-Dauber wasps.

Breeding

Adult male Black Widows wander in search of females but do not feed or bite. Females may occasionally kill and eat a male after mating but this is more the exception than the rule.

The female then lays several batches, containing up to 750 eggs each, in one summer. The egg case, about 1/2 inch in diameter, is suspended in the web. It is white to tan in color and has a paper-like texture. There may be 4 to 9 egg sacs produced during a summer. Normally, only 1 to 12 young survive after the egg incubation period of 14 to 30 days due to cannibalism.

The young Black Widows are colored orange and white when they emerge 1 to 4 weeks later. The female Black Widow may live for more than a year and a half. Growth requires 2 to 4 months, depending on availability of prey during which the females molt 6 to 8 times and the males 3 to 6 times. Females mature about 90 days after egg sac emergence and live another 6 months to a year. Males mature about 70 days after emergence and live only another month or two.

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