The Phidippus spiders are a genus in the family of jumping spiders, or Salticidae. These spiders are called "jumping spiders" due to their ability to leap. Phidippus spiders may also be identified by their green mandibles, which are called chelicerae. Utah's list of red Phidippus spiders are the red velvet jumping spider -- Phidippus apachaeanus and Phidippus clarus. The red velvet spiders are red on their abdomen and prosoma regions, while Phidippus clarus is only red on its abdomen. Both jumping spiders do not weave webs to catch prey, but leap onto their prey. For shelter, jumping spiders build silk tents in logs or under rocks.
All cobweb spiders belong to the family Theridiidae. Theridiidae spiders create triangulate webs to catch their prey and nest. These spiders are also known as comb-footed spiders, since they generate silk from their feet. Among Utah's red cobweb spiders are black widows, who belong in the Latrodectus genus. Black widows are solid black but have a red hourglass-shaped marking on their skin. This spider species is venomous, and bites from black widows must be treated immediately. Another Utah spider with red coloration is female candy stripe spiders, Enoplognatha ovata; the abdomen of this spider is solid white with a red stripe.
Two of Utah's orb weavers, the cat-faced spider and Aculepeira orb weaver, have red coloration. Both spiders are reddish-orange. The cat-faced spider, Araneus gemmoides, is identified by the shape of its abdomen, which closely resembles the ears and eyes of a cat. Aculepeira orb weavers, or Aculepeira packardi, have white markings on their abdomens; their abdomens are larger than the spiders' prosomas. Orb weavers receive their name from the shape of their webs, which are circular. Both of Utah's red-colored orb weavers are in the Araneidae family of spiders.
Scientifically known as Dysdera crocota, the pillbug spider has dark red prosoma and abdomen regions; the spider's legs are bright red. This spider species currently exists in Utah, but is an invasive species native to the Mediterranean countries. Pillbug spiders are called so because the staple of their diet is pillbugs. Other physical characteristics of pillbug spiders are large fangs and six eyes. Another name for the pillbug spider is the sow bug killer.