North America has approximately 3,000 species of spiders, but most of these do not pose a threat to humans. In fact, since they are predators, they do the avid gardener a great service when they kill insect pests. Spiders have eight legs, usually four pairs of eyes, an abdomen and a cephalothorax. If you want to identify the spiders in and around your home, the most distinguishing features are color and size. Several spiders, with black bodies and light and dark brown legs, exist in North America.
Ant Mimic Spider
At least two spiders exist that are nick-named "ant mimic spiders" with black bodies and brown legs. The Coleosoma acutiventer species has a shiny black body with reddish to light and dark brown striated legs. With a body length of approximately 1/5 inch, they look like ants because their abdomens are elongated and pinched to make them look like insects with three body segments. Slightly bigger than the Coleosoma species, Falconina gracilis is another spider species that looks similar to an ant. These spiders have a dark brown abdomen with an oval shape and a shiny black cephalothorax. They have amber to light brown legs segmented with darker color stripes.
False Black Widow Spider
The false black widow spider (Steatoda grossa) has this common name because it looks like the poisonous black widow spider. Both species have bulbous abdomens and black bodies, and build similar webs. But unlike the sheer black body and red hourglass marking of the true widow spider, the abdomens of false widows are marked with pale to golden markings amidst a black backdrop. False widows have dark legs with lighter brown markings. They range in size from 0.2 to 0.8 inches.
Red Widow Spider
Like the black widow, the red widow spider (Latrodectus bishopi) is poisonous to humans. If you think you have been bitten by one, immediately seek medical condition. Generally, red widows tend to be shy and will not bite unless they are disturbed. Where black widow spiders are completely black with a red hourglass marking on their undersides, red widows have reddish-brown legs and cephalathorax and a shiny black abdomen. Often the black abdomens are marked with a row of red spots. Adult red spiders may measure 1 1/2 inches when their legs are extended.
Ground spiders (Nodocion spp.) range in size from 0.08 to 0.7 inches. Their cephalothorax and abdomen are dark brown to black and shiny. Their abdomens are particularly distinctive with an elongated and flattened shape. Ground spiders legs are reddish brown with darker brown segments.