Black Widow Spiders are one of the two groups of medically important spiders in the United States. Three species of black widow spiders are native to the U.S., but only two are common around structures – the southern and western black widow spiders. Adult females of both species have shiny black bodies and globular abdomens with a red hourglass marking underneath, except the western black widow has an additional red spot above the tip of the abdomen.
Only black widow females can cause an envenomating bite to humans. They are usually brushed up against in their webs built-in quiet, protected places low to the ground. Their venom contains a neurotoxin that causes constant muscle contraction, which can produce severe pain that lasts for several days. Black widow spider bites do not develop necrotic lesions and are rarely fatal.
Heavy black widow spider populations are usually a result of poor storage practices, both indoors and outdoors. They are also common in crawlspaces. Wearing thick gloves while inspecting can help reduce the risk of a spider bite. Treat spiders and egg sacs directly with a knockdown product before removing their webs. Residual spot applications can be made to areas prone to web building.