Like all spiders, black widows have eight legs and no antennae or wings. Their bodies consist of two sections-the cephalothorax, which is the head and thorax together, and the abdomen. These two sections are connected by a tiny waist, called a pedicel.
Black widows also have eight eyes, with four of them being quite unique-on either side of their head, they have two eyes that are very close together and almost touch. The remaining four eyes are in the center, two in front and two behind. There is no other species of spider with this exact eye formation.
Black widow spiders' legs have three small claws on them, and their back pair of legs is covered with bristles. Their other characteristics vary by gender.
The female black widow is about half an inch in body length and reaches about 1-1/2″ including its legs. Her abdomen is large, shiny, and very rounded, almost a perfect sphere. Normally, the female's abdomen measures about ¼” in diameter, but it can be larger if she is carrying eggs.
The females usually look black or brownish-black in color. They have a unique marking that many people are familiar with: on the underside of the abdomen, the female bears two triangle shapes that look like an hourglass. These can vary in color from golden to orange to red. Sometimes these triangle shapes do not touch, and other times, there may only be one triangle-type marking.
Male black widows are considerably smaller than the females, about half their size, but have longer legs. The abdomen on a male looks more elongated and not as round a female's. They are sometimes lighter in color and have patterns or markings on the dorsal side of their abdomen, usually spots and lines that branch out to the sides. Young black widow spiders of both sexes look like adult males.