Learning to distinguish spiders from insects is the first step to identifying different species of spider. While insects have six legs, three body segments (head, thorax and abdomen), mandible mouth parts and usually have wings, spiders have eight legs, two body segments (head and abdomen), fangs for mouth parts and never have wings. Virtually all spiders are beneficial in the garden, as they eat insect pests, but those in the home can be a nuisance or even dangerous.
Determine the dimensions of the spider. Black widow females are usually 1/2 inch in length with rounded abdomens. The males are much smaller and brown. Parson spiders grow from 1/3 to 3/4 inches in length and have oval heads and abdomens.
Jumping spiders are usually less than 3/4 inch in length with oval heads and teardrop-shaped abdomens tapering to a point in the rear.
Check the length of the legs. Black widows have unusually long forelegs, while the other black spiders are of medium length and thin. Parson spider legs are medium length and thicker than those of the black widow. Many varieties of jumping spiders have short, thick and powerful legs while others have medium length and somewhat slim legs.
Examine the body for hairs. Black widows' body hairs are microscopic, making it appear hairless to the naked eye, and the black body is glossy in appearance. Parson spiders have very short hairs and slightly glossy bodies. Over 300 species of jumping spiders live in the United States; some have somewhat short body hairs while others are excessively hairy.
Look for characteristic markings. Black widows have a distinctive red hourglass shape on the bottom of the abdomen. Parson spiders have a small bar-shaped light discolouration on the top of the abdomen with an inverted V attached nearest the rear.
Black-coloured jumping spiders have a variety of abdominal markings from a simple dot to complex patters.
Determine the spider's environment. Black widows prefer warm climates, are common in America's Southwest deserts and live on the underside of plants, rocks, debris and ledges where it has room to spin a web. Black widows may move indoors in cold weather. Parson spiders live in all 50 states; they do not spin webs but instead hunt on foot.
Different species of jumping spiders live in different environments. Due to their diversity, they live in all 50 states in a variety of habitats. What jumping spiders all have in common is that they are active predators, usually day hunters and can jump between 10 and 40 times the length of their bodies.
Parson and jumping spiders are nonvenomous; however, some people have a bad allergic reaction to their bites. Black widows are the most poisonous of all North American spiders, though only 1 per cent of their bite victims die, usually small children.