They are generally unappreciated. But, in spite of their creepy appearance, most spiders are beneficial. They eat live insects, keeping them under control indoors and out.
Some spiders do bite humans. Only the black widow and the brown recluse have bites that can be fatal. There is an anti-venom of the black widow, but none for a brown recluse’s bite. (It can be treated with antihistamines, cortisone and antibiotics.)
The female black widow (only the female is poisonous) is half an inch long, with a red or yellow hourglass design on the underside of a shiny black body. But there are at least five different types in North America and not all of them can be depended upon to be black with a red mark.
These web spinners prefer dark places close to the ground and may live under furniture, in crawl spaces, outbuildings and debris. They’re most commonly found in warm climates, but may appear in other areas.
The brown recluse is also 1/2 inch long. It has a yellowish brown body and a distinctive, dark, violin-shaped mark on its head. Although mainly a denizen of the Southwest and West, it can be carried to other areas. It inhabits places similar to the black widow as well as in folds of clothing.
If you have a spider bite that is painful, red or swollen, assume it may be dangerous. Don’t wait for evidence of poisoning. And if sweating, vomiting, muscle cramps, joint pains, chills, fever or breathing difficulties develop, get medical help immediately.