Black widows are the better known spiders in the family Theridiidae. Members of the genus Latrodectus, these spiders have a toxic bite to humans. Although their bite does not cause death, symptoms include tachycardia, dizziness and muscle pain. In some species, females have red markings on their abdomen, but they can also have dark brown to gray bodies. Black species found in Nevada include Latrodectus hesperus and Latrodectus mactans.
Part of the family Theraphosidae, tarantulas are the largest spiders in the world, measuring up to 4 inches in body length in the tropics. Tarantulas have urticating hairs on their back, which they use for defense. Although most species found in Nevada are brown, the Aphonopelma paloma is a black species found in the state. False trapdoor spiders are members of the family Antrodiaetidae and include some black species, such as Antrodiaetus and Aliatypus, found in southern Nevada.
Also known as ground spiders, black members of the family Gnaphosidae found in Nevada include the genera Herpyllus and Sergiolus. Although most wolf spiders (Lycosidae) are dark brown, some species are black, often showing light or colorful markings on their backs. They are active hunters and feed on insects, captured on the ground. Black species that live in Nevada include some burrowing wolf spiders (Geolycosa).
Salticidae or jumping spiders measure up to 1 inch in body length. Active hunters, they can jump when hunting to catch their prey. A common genus in Nevada is Phidippus, often black with white or red markings. Part of the family Thomisidae, some black crab spiders of the genus Coriarachne are found in Nevada. These spiders are able to move backward and sideways, like crabs.