Only a few spiders in North America are poisonous to humans; these include the black widow spider and the brown recluse spider. Both prefer warm climates and dark, dry places where flies are plentiful; they often live in outdoor toilets, wood, rock, and brush piles or in dark garages and attics. Bites usually occur on the arms or hands of people looking for something in these places. Often, the person does not realize he or she has been bitten until a swelling or bite mark is noticed.
Punctures of the skin and/or envenomation by the fangs of a spider.
Nearly all spiders generate venom that aids in the demise of their prey. Nevertheless, merely a handful of species, like the North American black widow, pose a threat to humans. Fortunately, antivenoms exist as remedies for numerous potentially lethal spider bites.