Print This Page

Black Widow Spiders

Common name:

Black Widow

Size: Adult--9/16" to 1 1/2"

Identification: Adult females have shiny black bodies and a distinctive red hourglass-shaped marking on the underside of the abdomen. The compact webs are off-white and dense. Males are smaller and have markings on the upper side of the abdomen and large eyes.

Biology and life cycle:

Young spiderlings are whitish when first hatched but darken quickly. Females lay eggs in spring or summer in grayish silken egg balls. Females spin a small, irregular tangled web with a tunnel that she goes into when disturbed. These webs are usually close to the ground. Females eat the males after mating unless they are fast enough to escape. She lays up to 200 to 900 eggs in a sac within the web. The eggs hatch in about thirty days, have one molt, then escape the web and "balloon" to a suitable spot to settle in. Ballooning is done by spinning a strand of silk and letting the wind blow the spiderling to the new location. Young are cannibalistic--only one to twelve young survive from each egg case.

Habitat:

Buildings, rodent holes and burrows, barns, garages, basements, outdoor toilets, hollow stumps, trash, brush, vegetable gardens, and dense vegetation. They particularly like tomatoes and grapes.

Feeding habits: Mostly very small insects.

Economic importance: Bites can be very dangerous, especially to children and debilitated people.

Natural control: Mud daubers and predatory insects.

Organic control: Physical removal of webs. Outdoor toilets are the most common place where people are bitten. Spray  plant oil products or dust with natural diatomaceous earth.

Insight: Bites cause little or only momentary pain, but the poison causes severe cramping and aching pain from ten to sixty minutes after the bite. The pain spreads to all the skeletal muscles of the body and causes severe hardening of the abdomen. Most deaths are children and the sick and debilitated. Seek prompt medical attention.

Q:  I have killed almost a hundred Wolf Spiders in our house and garage; I have killed a few African Jumping spiders in my house, and had a Brown Recluse alive in our bath room. But now I am concerned, because tonight I had a female Black Widow in the middle of her web under my back patio door.  When I spray the spider with Spider Shot spray it does nothing, but wasp spray does kill them after I drench them. I am getting really concerned, because I have a three week old baby and a house full of spiders. What can I do to rid our house of the pests? I know they are suppose to be good for insect control, but considering a Black Widow has venom 15 times as potent as a Rattle Snake, I prefer not to have these spiders in or around my house. Insecticide is just not doing the trick.  J.R., McKinney.

 A:  The sprays you are using are far more dangerous to your child than the spiders. Although most of the spiders are non- poisonous, the orange oil sprays will kill them. Stomping on the individual ones works well. There's also good information in the Texas Bug Book. Wolf spiders and jumping spiders for example are non-aggressive, safe and very beneficial in helping to control pests.

For more information see the Texas Bug Book.
 

Female black widow from the upper rear, showing pattern.		Female black widow showing mouthparts.	Dorsal view. Note that the red dot is formed by this spider's spinnerets.

  Search Library Topics      Search Newspaper Columns