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Myths and a few fatal poisonings have made many people afraid of spiders. The only dangerous spiders in the northeast, however, are the very rare black widow and brown recluse spiders. These spiders are not native to the northeast, but may be occasionally transported here (the brown recluse is from the southwestern United States and the black widow is from the southern United States). Other spiders may be annoying due to their webs, but, unpopular as they are, most spiders are shy and harmless to humans. Most have fangs too small or weak to puncture human skin. They usually will not attempt to bite unless accidentally trapped or held. Spiders are beneficial, feeding on harmful insects (flies, crickets, etc.) and mites in and around the home, yard, garden and field Description: Spiders have eight legs (four pairs), and lack wings and antannae, but all vary in size, shape and color. They have two body regions: a cephalothorax (fused head with thorax) and an abdomen. Most spiders have eight eyes, some only six and several have fewer or none. All have a pair of jaw-like structures (chelicerae) which are hollow claw-like fangs through which venom can be ejected. The tip of the abdomen has silk-spinning glands. Young spiders (spiderlings) resemble adults except for their smaller size and coloration. Males are usually smaller than females. All spiders produce venom that is poisonous to their normal prey of insects, mites and other small arthropods. Venom is injected through the fangs to immobilize the prey. Since spiders can only ingest liquids, digestive fluids are either injected or regurgitated into the prey. Spiders produce silk, secreted as a liquid through the spinnerets, which hardens on contact with air. Different types and textures of silk may be used to construct snares or webs, egg sacs, draglines and ballooning threads. Some spiders use web snares to trap prey, and all species construct a silk sac to deposit eggs. Many spiders attach draglines of silk to the substrate at intervals wherever they go, appearing to have a silk thread to hang onto when knocked from their perch. Some spiderlings sail through the air (ballooning) on wind currents. Young spiders climb to a high point and release silk strands until the drag from the wind is sufficient to support their weight. They then release their hold and sail away, often for considerable distances. These ballooning threads (gossamer) can fill the air on clear days as spiderlings disperse to new areas. Life Cycle: Spiders lay eggs within a silken egg sac that is often ball-shaped and either hidden in the web or carried by the female. Spiders may produce several egg sacs, each containing several hundred eggs. One female may produce as many as 3,000 eggs in a series of several sacs over a period of time. Eggs may hatch a few weeks later (or the following spring). Spiders reach adulthood in one year. For a spider to grow, it must shed its skin (molt) usually four to twelve times before maturity. Most spiders live either one to two seasons. Spiders may overwinter as eggs, spiderlings in the egg sac, immature spiders living outside the egg sac or as adults. Common Household Spiders: Orb Weaver or Garden Spider (family Araneidae): These spiders all construct the characteristic circular, flat wheel-like web (orb web) in which flying insects are trapped. Some construct elaborate and beautiful, large webs in gardens and tall vegetation, especially obvious in the late summer and early autumn months. They have poor vision and locate the prey by feeling the vibration and tension of the threads in their web and then quickly, by turning the captive with their legs, use silk to wrap the victim. The prey is bitten before being carried to the center of the web or to a corner where it is eaten. Anything inedible is cut out of the web and dropped to the ground. In the fall, female orb-weavers die soon after producing egg sacs containing several hundred eggs. Eggs may hatch soon after or not until the following spring. Many adult spiders are large, some with oddly shaped abdomens (pointed spurs, conical tubercles, etc., in various colors of black, yellow, orange, red, white, brown, green, etc.). One common garden spider, known as the black and yellow garden spider, has silver hairs on the back of its forward body section and a large abdomen marked in black and bright yellow (or orange). The common garden spider is approximately 25 mm (1 inch) long and hangs head down in the center of the web. It is often found in brambles, bushes and tall grasses in open, sunny places near human habitations where flying insects blunder into the trap. Egg sacs are spherical and narrowed at one end and covered with a tough brown, paper-like silk. These spiders are not considered dangerous, despite their formidable appearance, but they can bite if handled or molested. Wolf Spiders (family Lycosidae): Female wolf spiders are large, hairy, running spiders, often confused with tarantulas. They may be brown, black, gray, white, yellow, orange or green. Many have a stripe or pattern the length of the first, and sometimes the second, body segment. They are nocturnal and usually occur outdoors but may wander indoors, especially into cellars and basements in late summer and fall when cooler temperatures prevail. These hunting spiders, which do not construct webs, carry the large, globular egg sac attached to spinnerets under the abdomen. Upon hatching, the spiderlings climb onto their mother's back and ride there for several days before dispersing. They do not establish themselves indoors and are not aggressive, but may bite if handled or molested. Jumping Spiders (family Salticidae): These common spiders are no more than 12 mm (1/2 inch) long, and are striking in appearance, with bright colors often heightened by iridescent scales. They are hairy and short-legged and can jump several times their own length. Some are black with spots of orange or red on the top surface of the abdomen; others are brownish-gray and yellow with whitish markings. Their movements are quick (irregular gait) with short, sudden jumps. Jumping spiders are active during the day and like sunshine, normally living outdoors, but are sometimes found indoors on walls, windows, screens, doors, etc. They are sometimes carried indoors on firewood. They depend on their vision (keenest of all spiders) and leaping ability to catch prey, especially flies. After mating, the female constructs a silk cocoon for her eggs and guards it. Some can bite humans if handled. House or Cobweb Spider (family Therididae): The female house spider is larger than the male, about 10 mm (1/3 inch) long, gray to brown with a rounded, globular abdomen mottled with several dark stripes on the upper side. House spiders spin their webs in dark corners of moist rooms and outdoors. They hang upside down in the center of an irregular cobweb. Sticky threads on the outside of the web entangle many insects, especially flies, which are bitten and sucked dry. Females are fertilized several times during a lifetime and lay up to nine egg sacs, each containing 200 or more eggs. Young hatch in about eight days, staying within the sac until after the first molt. Spiderlings take several months to mature. Cellar Spiders (family Pholcidae): Cellar spiders have bodies which are about 2-6 mm (1/16-1/4 inch) in length and long, slender legs. Although similar in appearance to daddy-long-legs, cellar spiders have rounded or elongate bodies which are light-colored, gray or brown. Common in barns, cellars and damp warehouses, they hang upside-down under sheetlike or irregular webs.
Poisonous Spiders: Brown Recluse Spider (Loxosceles reclusa): Brown recluse spiders belong to a group of spiders commonly known as violin spiders or fiddlebacks, because of a characteristic fiddle-shaped pattern on their head region. The brown recluse is golden brown with a dark brown or black "fiddle," which is often shiny. They range from 5-15 mm (1/4 to 3/4 inch) long. Brown recluse spiders are found primarily in the South and Midwest. They are rarely, if ever, found in Rhode Island. Brown recluse spiders live in basements and garages of houses, often hiding behind boards and boxes. Bites sometimes occur when the spiders hide in towels or clothing. They are seldom aggressive and bite only when threatened or injured.
The severity of the bite of the brown recluse may vary from no symptoms at all to a reaction that is very severe. Often there is a systemic reaction within 24-36 hours of the bite characterized by restlessness, fever, chills, nausea, weakness and joint pain. There is often tissue death at the site of the bite. In some severe cases, a wound may develop that lasts several months. In all cases, a physician should be notified. If at all possible, kill and take the spider to the physician for positive identification. It is important to note that many wolf spiders are similar in appearance to the brown recluse, but the wolf spider is hairy, larger and more robust than the brown recluse. Black Widow Spider (Latrodectus mactans): Like the brown recluse, black widow spiders are not generally found in Rhode Island, except when brought here by travelers. The female is usually black with a red spot or hourglass-shaped mark on its round abdomen. The male usually has light streaks on its abdomen. The spider is about 38 mm (1 1/2 inches) in diameter, including legs. In infested areas, black widow spiders are common around wood piles, and are frequently encountered when homeowners carry firewood into the house. They are found under eaves, in boxes, outdoor toilets, meter boxes and other undisturbed places. The female black widow occasionally eats the male after mating (hence the name). She hangs belly-upward and rarely leaves the web. The black widow is not aggressive, but it will bite instinctively when touched or pressed. Be very careful when working around areas where black widow spiders may be established. Wear gloves and pay attention to where you are working. Black widow bites are sharp and painful, and the victim should seek medical attention immediately.
Control: Sanitation is critical in successful spider control. Indoors, the spiders, webs and egg sacs can be collected and destroyed with a strong suction vacuum cleaner. Move and dust often behind and under furniture, stored materials, wall hangings and corners of ceilings. Eliminate other household pests (prey) such as flies, ants and pantry pests, which attract spiders. Be sure to control excess moisture and humidity, keeping basements, crawl spaces, porches, etc., as dry as possible. Outdoors, clean up woodpiles, trash, rocks, compost piles, old boards and other debris around the house foundation where spiders often live. Be sure to seal or caulk cracks and crevices around windows and doors and install tight-fitting screens as needed where spiders can enter the house. Use a hose with high-pressure water on the outside of the house to knock down and destroy webs, egg sacs and spiders. Use yellow or sodium vapor light bulbs at outside entrances to reduce night-flying insects (prey) which attract spiders. We generally do not recommend insecticides for spider control, but when necessary, spiders can be killed with aerosol cans of either flying insect killer or residual sprays such as crack and crevice sprays.
Adapted from the Virginia Cooperative Extension and the Ohio State University Extension, 1999
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