The black widow is what many people envision when they think of a dangerous spider. Phoenix is one of the most common places for black widows to reside; our dry, hot climate provides the spider with optimal conditions. Recent heavy rainfall coupled with black widow’s desire to nest in damp, dark places has heighten infestation concerns. It is crucial to be able to become knowledgeable on how to identify these eight-legged pests, as well as what preventative steps needed to keep them out of your home.

Here are some easy tips on the how to identify black widow spiders and how to make sure they do not become another home guest.

Identification

Adult female black widows are glossy black to very dark brown in color, with a large rounded or oval abdomen. The characteristic orange or bright red hourglass marking is found on the underside of the abdomen. When mature, female black widows can measure up to 1.5 inches, including leg span. Male black widows are roughly half the size of females, and do not have the red hourglass marking. They are light brown or tan in color with white stripes. A black widow can reproduce year-round, but even more in the summer months, producing up to nine egg sacs each containing about 400 spiderlings.

Newly hatched black widows are white with black spots on their abdomens, with a cream-colored hourglass marking. As they mature, they become cream and brown striped.

Black widows are common in the warm desert environment in Arizona, and like to build their webs in dark, sheltered areas. Black widow webs may be seen under rocks, under steps, or around decking near your home. Black widows are also sometimes found in children’s sandboxes and play equipment, or wood piles and shrubs. They are nearly always outdoors, but sometimes black widows will build their webs in a secluded indoor area, like a garage, basement or closet. Black widow webs are not uniform in nature and have a cobweb appearance.

Venom

Black widows are typically shy and not inherently aggressive spiders, but will become aggressive when defending her eggs. However, because they actively hide in dark, low-to-the-ground places, they are frequently undetected until a bite occurs, usually by an unaware person who steps into a nesting area. Male black widows are harmless, but venom from the female black widow can be highly toxic to humans. Reactions to black widow venom can vary depending on the location of the bite, the amount of venom injected, and individual sensitivity to the venom. It is important to keep a lookout for black widows in your home, and proactively receive proper preventative treatments to avoid infestation. If a person is bitten, contact a local poison control center immediately, and attempt to capture the spider for identification.

Prevention

Black widow spiders do not hunt humans, and will usually only bite when provoked or trapped, or when they are protecting their eggs. For this reason, be careful when moving items that have been in an undisturbed area for a long time, such as stored lawn furniture or flower pots.

Control other pests around a home to remove the food source for black widows. Taking care of pests such as roaches and crickets will remove an easy food source for the spiders, which will make a home less inviting.

Keep outdoor areas clean and free of debris, and reduce the areas of suitable habitat around a home. Clean up wood piles or piles of yard waste, and regularly clean empty, enclosed spaces near the foundation. Tidy up storage areas, and clean up any unneeded items, boxes or stacks of debris in garages, sheds and basements. Keep landscaping plants trimmed and away from the foundation of homes. If webs are seen, use a broom or vacuum to destroy them. Use a fly swatter to kill black widows if they are seen around a home.

• Curtis Whalen and Nate Woolf are the co-founders of Blue Sky Pest Control.

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