Black widow spiders spin webs to trap their prey, which consists of a variety of insects such as ants, beetles, caterpillars, and cockroaches. These webs are very irregular with no obvious pattern and look like a mass of fibers, though the silk is quite strong. An average web is about one foot across and has a small spot in the middle where the spider will wait for its prey. A web is usually situated near the ground in a dark, sheltered location.
Outside, black widows usually make their webs in protected areas, such as woodpiles, under decks and rocks, in tree stumps or other hollow places. They prefer dry areas like sheds, barns, woodpiles, or barrels.
Inside, these spiders are usually found in low-traffic areas like basements, crawl spaces, or garages. They prefer areas that are cluttered because they can find more insects to eat.
The female will spend time in the web during the day and rarely leaves voluntarily. She tends to hang upside down in the web, which exposes her hourglass marking that serves as a warning to predators. When prey gets caught in the web, she will wrap it in silk, then inject it with her venom to kill it. If a female has egg sacs in her web, she will stand guard against predators and is more likely to attack at that time.