Spiders are rarely dangerous and benefit flowers, plants, and gardens by removing insects and predators from foliage. A few spiders in Colorado can hurt humans but only do so when their web is threatened. Coloradans should become familiar with the Latrodectus species and wear gloves while gardening or working with dirt. Although uncommon, these spiders can cause asphyxiation and allergic reactions. Not many spiders in the United States are poisonous. Colorado is no different, and people should know how to identify the black recluse and black widows.