There are about 1000 species of spiders in the United States. They live everywhere, including homes and buildings. Some species are able to bite humans and inject venom into the skin. The brown recluse and the black widow are considered venomous spiders. However, most spiders are not harmful to man.
All spiders have 8 legs and 2 body regions. They are predators, feeding primarily on insects and other arthropods. When feeding, spiders inject a digestive fluid into their prey, and then suck up the digested food. They can survive for long periods of time without feeding.
Spiders are of interest because some enter homes, some are considered poisonous and still others are raised as pets. Several species of spiders enter homes and become a nuisance. When numerous, spiders are annoying because they construct webs. Abandoned webs collect dust, resulting in cobwebs. However, spiders are considered beneficial because they feed on insect pests.
Because spiders feed entirely on living insects, they may search actively for their prey, hide and wait for them to pass, or build webs to trap insects. Most web-building spiders build and abandon several webs per year. Webs are produced by glands on the spider's abdomen. Silk is a liquid, which hardens when exposed to air, and is used to construct webs, safety lines, egg sacs and even parachutes.
Spiders reproduce by laying eggs in silken sacs. The egg sac is either carried around by the female or hidden in the web. Each egg sac may contain several hundred eggs, which hatch in 2 - 3 weeks. Young spiders mature to adults in about 1 year. Spiders live separately and only come together to mate. Males are usually smaller than females with different color markings. Newly hatched spiders are tiny and can easily enter homes through screens and loose fitting doors and windows. If insects that they eat are not plentiful, spiders are less likely to infest a home.
Almost all spiders found in the United States are harmless to humans and most species do not attempt to bite unless they are provoked. Spiders usually remain hidden and do not seek out humans to bite. Most spiders cannot penetrate human skin with their fangs. Almost all spiders possess venom, but only a couple are considered dangerous to humans, such as the brown recluse and black widow.
The brown recluse spider is recognized by the distinctive dark violin-shaped mark located on its head and thorax. It is a medium size spider, about 1/4" - 1/2" long. It is light tan to deep reddish brown. It is usually found in sheds, garages and areas where items are stored. It may hide in arms or legs of stored garments or in beds that have been unoccupied for some time. Persons bitten by the brown recluse usually do not feel the pain for 2 - 3 hours. A blister arises followed by inflammation. Eventually, the tissue dies leaving a sunken sore, and may take 6 - 8 weeks to heal.
The black widow spider is glossy black and has a complete, red hourglass marking on the underside of its abdomen. It is usually found outdoors, in protected areas, such as under rocks and boards, and in and around old buildings. With its legs extended, the black widow is about 1 1/2" long.
The bite of the black widow spider feels like a pin-prick. The initial pain disappears rapidly, leaving local swelling and 2 tiny red marks. Muscular cramps in the shoulder, thigh and back usually begin within 15 minutes to 3 hours. In severe cases, pain spreads to the abdomen. Death seldom occurs if a physician is consulted and treatment is prompt.