WSU CAHNRS

College of Agricultural, Human, and Natural Resource Sciences

Department of Entomology

Black Widow

Insects &
Arthropods

Black Widow Spider
Blister Beetle
Box Elder Bug
Cat Face Spider
Cat Flea
Cereal Aphid
Cereal Leaf Beetle
Cicada
Corn Earworm
Crab Lice
Cooley Spruce Gall Adelgid
False Wire Worm
European Mantis
Housebug
Jumping Spider
Juniper Scale
Locust Borer
Minute Pirate Bug
Mosquito Diseases
Northern Scorpion
Rose Curculio
Russian Wheat Aphid
Snowball Aphid
Ten Lined June Beetle
Thrip
Western Yellow Striped Army Worm
Wheat Stem Sawfly
Wire Worm
Wooley ash aphid
Yellow Jacket Wasp
Yellow Sac Spider

 

Order Arachnida – Family Theridiidae, Comb-footed Spiders

Description: Male 1/8″ (3-4 mm), female 3/8″ (8-10 mm) and black. Male’s abdomen elongate with white and red markings on sides. The female’s abdomen is almost spherical, usually with a red hourglass mark below or with 2 transverse red marks separated by black (more common in Tri-State region.  The legs of the male are much longer in proportion to his body than those of the female. Spiderlings are orange, brown, and white, gaining more black at each molt. Juvenile females often migrate away from their mothers in the spring and are scary in homes when this happens.

Black widow spiders feed on any insect that gets into the web, usually located in a dark, dank, site like a water meter box, or in a building crawl space. Wood piles are common sources of bites on humans where the spider bites the arms or abdomen of a person carrying wood into the house. The web is irregular with a funnel shaped retreat for the spider at one side.

 

The female rarely leaves web, stays close to her egg mass, biting defensively if disturbed. The male comes to the female’s web to mate, and is usually killed and eaten by the female. Some males offer a food item tied up in silk to the female to distract her. The male may escape, but mates only once and dies. The egg sac, 3/8-1/2″ (8-12 mm) wide, is pale brown to white. The female stores sperm, producing more egg sacs without mating again. Spiderlings disperse soon after hatching. Some females live more than 3 years.

The Black Widow spider often attempts to escape rather than bite, unless it is guarding an egg mass. Males do not bite. Female Black Widow spiders provide very toxic bites to humans and are a dangerous spider with a cosmopolitan distribution. They were the most common spiders in the area until the Hobo (aggressive) spider invasion began.

Department of Entomology, Washington State University, Pullman, WA, 99164-6382 USA, 509-335-5422, Contact Us
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