Brown recluse spider
This small spider, which is found in the lower Midwest and South, packs a wallop with its bite. Its venom can create skin necrosis, a serious condition where healthy skin rapidly dies off. However, the brown recluse is also painfully shy and is also reluctant to bite. "It's a creature that a great many urban legends have formed around," says Heydon. "It's not some blood thirsty monster. Most people who have them in their house don't even know they're there." To keep out the recluse or other spiders like the black widow, clean up cluttered corners of your yard and garage, try using a yellow-tinted outdoor light to repel the bugs that spiders like to feed on and make sure your door sweeps are intact.