Black Widow Spiders, Black Widow Control

Location of the Black Widow

The Black Widow can be found in all 50 states and is very common in California and the Southwest. Black widows are also found in such countries as Canada, Mexico, Russia, New Zealand, Australia, and warmer parts of the world, such as the Mediterranean.

Biology of the Black Widow

Latrodectus mactans

Male Black Widow: The average male matures in about 71 days and lives for a maximum of 160 days. Males are approximately ½ the size of the female and are not considered dangerous.

Female Black Widow: The most well known widow is the female Southern Widow Spider, which has the reddish hour glass marking on the abdomen and is nearly ½ inch in size. A female may produce four to nine egg sacs during one summer, containing 300-400 eggs per sac. One generation per year is standard. The female Widow matures in approximately 179 days and can live up to 550 days.

Black Widow Food Sources:

The Black Widow is a carnivore and feeds on many insects but also consumes wood lice, diplopods, chilopods and other arachnids. Contrary to popular belief, females rarely consume males following mating, in fact, males live longer due to mating.  This is because males act as parasites and feed on prey captured by the female.

Black Widow Habitat and Range:

Black Widows build retreats close to the ground and in dark areas.  Widows venture indoors in search of a dry shelter. Females construct webs in areas such as hollow logs, under loose bark or stones, in small trees and under bushes. Man-made habitats include crawl spaces under houses, firewood piles, under boards and furniture, inside boxes, in seldom-worn shoes, behind and under debris, drainage pipes, false ceiling areas, out-houses, sheds, barns, well houses and root cellars.

Predators of Black Widows:

Parasites of Widow egg sacs include the scelionid wasp, and members of the chloropid fly genus Pseudogaurax. Predators of the adult spiders include a few wasps, most notably the blue mud dauber and spider wasp.

Black Widow Attacks:

After laying eggs, the female Black Widow tends to become hungry and more likely to bite if her web is disturbed. While the Black Widow bite is highly poisonous, the spider seldom bites people.  These poison bites are usually the result of the spider accidentally becoming trapped against the skin. The black widow spider has neurotoxic venom and is considered the most venomous spider in North America. The female injects such a small dose of venom that it rarely causes death.  Reports indicate human mortality black widow spider bites at less than 1%.

Health Issues

Allergic reactions or irritation can occur from the inhalation of hairs or scales of spiders. “Severe cramping or rigidity may occur in the abdominal muscles. Other symptoms from bites may include nausea, profuse perspiration, tremors, labored breathing, restlessness, increased blood pressure, and fever. Symptoms often diminish after a day or so and cease after several days.”

Medical Treatment for the Black Widow Spider Bite

If bitten, remain calm, and immediately contact your physician, hospital, or poison control center. Apply an ice pack directly to the bite area to relieve swelling and pain. The bite area should be washed immediately with soap and water and a disinfectant applied to help prevent bacterial infection.  Latrodectus anti-venom is effective for all species of widow spiders, but is usually restricted to the more severe poisonings that do not respond to the above measures or when the victim is pregnant.

Pest Control for the Black Widow Spider

Inspection/Identification: An inspection inside and outside the building is necessary to determine the type of spider, the sources of the infestation, how they are entering, and any contributing conditions.

The inspection of:

• Garages
• Crawlspaces
• Attics
• Basements
• Look for the presence of webs and checking for spiders hiding underneath items.

Non-Chemical: Elimination of conditions contributing to the entry of any spider is crucial to gaining control of an infestation.

Spider proofing methods include:

• Exterior lighting alterations
• Eliminating potential harborages
• Removing spider webs outside
• Sealing cracks
• Installing screens
• Improving attic and crawlspace ventilation.
• Cutting heavy vegetation near the foundation.
• Vacuuming, for removal of existing spiders, webs, and egg sacs.

Chemical: A non-residual insecticide applied into likely harborage sites can flush hiding spiders.  Non-residual aerosol insecticides can be directly applied onto exposed spiders.  Residual insecticides can be applied to small surface areas where spiders may crawl or construct webs. The application of liquid residual wettable powder (WP) or micro-encapsulated (ME, CS) formulation to likely web-building sites such as: corners, behind and under furniture, and behind stored items can be helpful in preventing new spiders from becoming established.

Hearts Pest Management has a comprehensive program that allows you to pick from standard chemicals or our latest organic pest control.  Both are effective in elliminating  black widow spiders.  We are the first and only EcoWise Certified company in Southern California.

Black Widow Resources

Mallis, Arnold, Handbook of Pest Control: The Behavior, Life History, and Control of Household Pests, 9th ed., “Species or Groups of Importance.” (2004): 935.

Mallis, Handbook of Pest Control, 936.

Matthew McCorkle, University of Michigan Museum of Zoology Animal Diversity Web, “LATRODECTUS MACTANS: Black Widow Spider,” University of Michigan, http://animaldiversity.ummz.umich.edu/site/accounts/information/Latrodectus_mactans.html (accessed May 28, 2008).

Mallis, Handbook of Pest Control, 936.

McCorkle, LATRODECTUS MACTANS.  (accessed May 28, 2008).

Karen M. Vail, Carl Jones, and Harry Williams, “The Black Widow Spider,” Agricultural Extension Service University of Tennessee, no. 1193 (2002): 5. (accessed May 29, 2008).

Wikipedia, Black Widow Spider, http://en.wikipedia.org/wiki/Black_widow_spider, (accessed May 28, 2008)

Mallis, Handbook of Pest Control, 935-36.

Mallis, Handbook of Pest Control, 942.

Susan C. Jones, Ohio State University, Ohio State University Extension Fact Sheet: Black Widow Spider, http://ohioline.osu.edu/hyg-Fact/2000/2061A.html (accessed May 28, 2008).

Mallis, Handbook of Pest Control, 942.

Jones, Ohio State University Extension Fact Sheet, (accessed May 28, 2008).

Jones, Ohio State University Extension Fact Sheet, (accessed May 28, 2008).

Mallis, Handbook of Pest Control, 946.

Mallis, Handbook of Pest Control, 947.

Mallis, Handbook of Pest Control, 947.

Mallis, Handbook of Pest Control, 953.

Mallis, Handbook of Pest Control, 949.

Mallis, Handbook of Pest Control, 954.

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