Black Widow Spider

Photo credit: John Jackman.

Article author: Mike Merchant
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Black Widow Spider

Description

Shiny, black spider with globular abdomen, usually with two reddish, triangular shaped markings on the underside of the abdomen. These markings often are joined to form an hourglass shape. The red markings vary among individuals and may look merely like spots, or a row of red spots may occur on the top of the abdomen. Immature spiders have white, yellow, orange or red markings on the top of the abdomen. The egg sac is free (not attached to flat surfaces). It is tan with a tough papery texture and is spherical with a nipple on the tip.

Origin and Distribution

Four structure-infesting species of widow spiders are found in all 48 states in the continental U.S.

Habitat & Hosts

They are not common indoors, but they are found in undisturbed sites such as basements and storage areas and prefer cluttered areas. Webs are built between stationary objects and walls. Outdoors, they prefer protected places near the ground, such as under stones, pieces of wood or brick piles or in rodent burrows and hollow tree stumps. Their favorite places are barns, sheds, meter boxes, brick veneer, barrels and woodpiles.

Widows tend to be clumsy out of their web and bites usually only occur if a hand is stuck in the web, or if a spider is inadvertently grabbed while cleaning areas like a garage or shed. Black widows come out at night and hunt in their cobweb-like webs. Since black widows don’t move easily, they wait for prey to come to them.

Life Cycle

Egg, spiderling (nymph) and adult. Lay eggs in a loosely woven cup of silk

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Using a flashlight, inspect corners, along edges, by light fixtures and windows as well as under cabinets and furniture. If moving any objects for inspections, wear gloves to avoid any bites. Outside inspect along the foundation of the structure, especially near areas with landscaping. Check electrical boxes, irrigation boxes and other protected areas. Use glueboards/ sticky traps in suspected areas of infestation to monitor spider populations.

Interior or exterior insecticidal sprays are generally ineffective at reducing spider populations, but may provide some repellency.

Insecticidal dusts can be used in low traffic areas such as boiler rooms, crawl spaces, and voids for long residual control of spiders.