This photograph of a female black widow and her egg case was taken at the Arizona-Sonora Desert Museum by Judi Moreillon.
Desert Duets: Black Widow Spider Babies Web Page
Black widow spiders mate in the spring. The female lays up to 750 eggs in a white or tan egg case that is 1/2 inch around. She lays eggs 4 to 9 times during the summer months. The eggs incubate for two to four weeks. Spider babies are called spiderlings. Only a small number of spiderlings survive from each batch of eggs because the babies eat each other!
The spiderlings are yellow or orange and white and become blacker with each molt. The rate at which spiderlings grow depends on their food source and their sex.
The larger female black widow spider takes longer to grow up and lives 3 to almost 5 times as long as the male.