How to Determine If a Spider Is Poisonous in North America

Although there are several North American spiders that have poisonous bites, only six are dangerous to humans. Of these, only two are considered deadl-- the brown recluse and the black widow spider. Learning to identify poisonous spiders can help you avoid a trip to a emergency room.

Instructions

    • 1

      Check the back. Is the spider brown with a dark violin-shaped mark on its cephalothorax (the body segment the legs attach to)? If so, then it is a deadly brown recluse spider.

    • 2

      Check the abdomen. Does the spider have distinctive yellow or red marks on the underside of the abdomen? If so, then it is probably a deadly black, brown or red widow spider. The marks may or may not resemble an hourglass--consider any mark an indication that the spider is a widow. Some widow spiders also have marks on the back of the abdomen. Is the spider brown with chevron-shaped marks on the abdomen and you live in the northwest part of North America? If so, then it is a poisonous hobo spider. Male hobo spiders have mouth parts that look like boxing gloves.

    • 3

      Check for burrows. Is it a large, fat, black spider with fangs? Then it is a poisonous mouse spider. Male mouse spiders have red heads. Both live in deep ground burrows. Is it a mottled gray and brown spider found in or near a silk-lined burrow on the ground? It may be a poisonous wolf spider.

    • 4

      Check the body. Is it a small black spider with a velvety covering on its body? It may be a poisonous black house spider, especially if it was found in or near a messy web.

    • 5

      Check the color. Is the spider yellow? It may be a poisonous species of yellow sac spider.