Identifying Marks on Spiders

Spiders are often difficult to identify because many species look alike. Some spiders, however, have distinctive markings on their bodies which allow for easier identification. If you see a spider, pay attention to these markings in order to determine the species and the potential danger. Detecting spider species is helpful for learning how to avoid venomous spiders and knowing when to allow the harmless varieties to stay in your garden for pest control.

Locate and inspect the spider in question. Without getting too close, so you avoid being bitten.

Take a picture of the spider, if necessary. If you don't have a camera handy, draw a quick sketch of the spider noting any distinctive markings on its body.

If the spider is black and about 1/2 inch long, look for an hourglass-shaped marking on the underside of its abdomen. If the hourglass shape is red or orange-yellow, it is likely that the spider is a black widow. Black widows are extrememly dangerous. Their bites are painful and in rare cases, deadly.

If the spider is brown in color and about 1/3 to 2/3 inch long, look for seveal light colored chevron shaped markings on its body. If you see these markings, the spider is likely a hobo spider. Hobo spiders are dangerous. Their bites are initially painless, but a bite victim can become very ill about 24 hours later.

If the spider is dark brown or black and about 1 1/2 inches in length, look at its head. If it has a red marking across most of the back of its head, this may be a mouse spider. Mouse spider bites are very painful and can cause severe illness.

If the spider is gray in color and about 1/2 to 1 inch in length, look at its back. If it has a dark gray marking that appears much like a union jack, this is probably a wolf spider. Wolf spider bites are painful, but not fatal.

If the spider is about 1/4 to 1/2 of an inch long with distictive yellow and brown stripes across its abdomen, it may be a St. Andrews Cross spider. St. Andrews cross spiders are not dangerous to humans.

If the spider is brown and about 1/4 to 3/4 of an inch in length, look for a dark brown violin-shaped marking behind its head, with the violin neck pointing down towards the abdomen. If you see this marking, this is a brown recluse. The brown recluse is extremely venomous. Its bite is painful and can cause severe reactions and even death.

Do not go near a spider or handle it. Many venomous spiders, such as the black widow, brown recluse, and mouse spider are extremely dangerous.