Many spiders have yellow and red markings. These bright colours can cause people to worry that the spiders might be poisonous, but the only venomous spider in the United States that has red markings is a black widow. These spiders have no yellow markings. In order to accurately identify a spider, it's important to gather as much information about the spider's shape, size and location as possible.
Jumping spiders are distinguished by their short legs and hairy bodies. These spiders have particularly acute vision, and their eyes are often visible from a distance. These spiders are named for their impressive jumping abilities --- they can jump up to 40 times their own height. These spiders are most frequently found in warm, moist locations and may live near water or in basements and showers. They come in many colours and may have red or yellow bands across their bodies.
The black and yellow argiope is an orb weaver spider that is common throughout the U.S. These spiders have large, rounded abdomens, and are black with red or yellow spots. They frequently build webs in shrubs and gardens. Interestingly, they eat their webs each night and then build a new one. Argiopes prefer bright and sunny areas and may occasionally build webs indoors near windows.
Crab spiders are named for their crablike bodies. These spiders have a large abdomen with horns and spikes. They frequently have both red and yellow spots or bands of colour. Though these spiders can look intimidating, they are not venomous and do not behave aggressively. They do not normally live inside homes.
Several other spiders have yellow or red markings but not both. Yellow sac spiders are common garden spiders that have yellowish bodies. Their bites can be very painful, similar to a wasp or bee sting. Black widow spiders, the best-known venomous spider, have red markings that are typically formed into an hourglass shape. Some species of tarantulas have red or yellow bands on their legs, but these tarantulas are not found in the U.S.