Black Spiders in Utah: Are They Dangerous?

Quick Take

• Black widow venom is more toxic drop-for-drop than rattlesnake venom, but that comparison tells only half the story about how dangerous a bite actually is. Black widow venom facts →
• One of Utah's largest black spiders can span over 3 inches and never leaves its burrow, and its hunting strategy breaks every expectation you have about how spiders ambush prey. Meet Utah's largest spider →
• The spider that looks most dangerous in Utah isn't the one you actually need to watch for in your backyard. The real backyard threat →

There are several black spiders in Utah, including the Western black widow, the Utah crab spider, the bold jumping spider, the burrowing wolf spider, and the Grand Canyon black tarantula. While most of these spiders may look dangerous, not all of them are. Most of the black spiders in Utah do not pose a threat to humans. The vast majority are harmless, beneficial predators that feed on insects. The black widow is considered the most medically significant spider in Utah, though rare desert recluse spiders in southern Utah may also pose a risk. Continue reading to learn more about five black spiders in Utah.

Western Black Widow

There are numerous species of black widow spiders, only the Western Black Widow (Latrodectus hesperus) is found in Utah. The Western black widow is prevalent throughout Utah, particularly in Southern Utah, although their territory has been spreading northward as the climate warms. Black widows thrive in warm, dry climates, favoring dark, undisturbed areas like garages, woodpiles, window wells, and spaces beneath landscaping.

Females are more dangerous than males because their larger size allows them to inject more venom when they bite. ‘Black widow venom is extremely potent, often described as more toxic drop-for-drop than rattlesnake venom, but black widows inject much less venom, so their bites are rarely life-threatening to healthy adults.

Utah Crab Spider

There are several black crab spider species in Utah, including the Utah Crab Spider (Bassaniana utahensis). The Utah black crab spider is a small, bark-dwelling spider. Adults of this species have a leg span of no more than 0.67 inches.

Utah crab spiders don’t spin webs; they are ambush predators that feed on a wide variety of insects visiting flowers, including honeybees, flies, butterflies, and beetles. Utah crab spiders pose no harm to humans. Instead, they benefit humans by eating mosquitoes and other bothersome insects.

Bold Jumper

The bold jumping spider (Phidippus audax) is a common, harmless North American spider that is found throughout Utah. Bold jumpers have a black body, metallic green or blue chelicerae (food-catching claws located at the front of the mouth), and a distinct white, yellow, or orange triangle on their abdomen.

These active, daytime hunters do not build webs to catch prey. They are ambush predators that actively stalk and pounce on prey. They use their large, sharp eyes to spot prey from a distance, creep closer, and then leap up to 50 times their body length to catch insects, securing them with a silk safety line. Bold jumpers are tiny spiders that pose no threat to humans.

Burrowing Wolf Spider

The burrowing wolf spider (Geolycosa rafaelana) is a large, predominantly black spider native to the desert and scrubland habitats of Utah. This spider is quite large compared to others in this article, with a body length between 1 and 1.5 inches and a total leg span that can exceed 3 inches.

Burrowing wolf spiders live in open, sandy, or scrubland habitats, where they build deep, vertical, silk-lined burrows that they rarely leave. They are sit-and-wait predators that use their burrows as traps instead of spinning traditional webs.

Although burrowing wolf spiders are venomous, their venom is not medically significant for humans. They are generally shy, keeping to themselves in their burrows, and are unlikely to bite unless severely provoked or handled.

Grand Canyon Black Tarantula

The Grand Canyon black tarantula (Aphonopelma marxi) is a large, hairy spider found in the arid, high-elevation regions of Utah. With legspans of up to 4 inches, these spiders may look intimidating, but they are not aggressive, and their bite is generally not considered medically significant for humans.