William F. Lyon
Myths and a few fatal poisonings have made many persons afraid of spiders. The only dangerous spiders in Ohio are the black widow spider, brown recluse spider and tarantula (sold as pets). Others may be annoying by their habit of building webs across doorways, in corners, on furniture and in other places. Unpopular as they are, most spiders are shy and harmless to humans. Most are quite beneficial by feeding on harmful insects and mites in and around the home, yard, garden and field. Wholesale destruction of spiders should be avoided, if possible. Some southern states not only tolerate spiders but encourage them to inhabit the house as an aid in nuisance insect control.
Spiders have 8 legs (4 pairs), vary in size, shape and color, and lack wings and antennae. Their body regions consist of 2 parts: a cephalothorax (fused head with thorax) and an abdomen. Most spiders have 8 eyes, some only 6 and several have fewer or none. All have a pair of jaw-like structures (chelicerae) that are a hollow claw-like fang 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.
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 (3 weeks or the following spring) and reach adulthood in 1 year. For a spider to grow, it must shed its skin (molt) usually 4-12 times before maturity. Most spiders live either 1-2 seasons. Some spiders may overwinter as eggs, spiderlings in the egg sac, immature spiders living outside the egg sac, or as adults.
All spiders produce venom that is poisonous to their normal prey of insects, mites and other small arthropods. Venom is injected through the hollow fangs to immobilize the prey. Since spiders can only ingest liquids, digestive fluids are either injected or regurgitated into the prey.
Spiders produce silk that is secreted as a liquid through the spinnerets and hardens on air contact. 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 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. Then, they 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.
Female wolf spiders are large, up to 1/2 inch long, hairy, running spiders, often confused with tarantulas. Their bodies are covered with shades of 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. Most are dark brown, large and run rapidly after prey. They are nocturnal, occur outdoors but may wander indoors, especially 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 several days before dispersing. They do not establish themselves indoors and are not aggressive, but may bite if handled or molested.
These common spiders are about 1/2 inch long or smaller, attractive, and brightly colored, often with iridescent scales. They are hairy, stockily built, 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, at times confused with black widow spiders. Others are brownish-gray and yellow with whitish markings. Their movements are quick (irregular gait) with short, sudden jumps. These jumping spiders are active during the day and like sunshine, normally living outdoors but are sometimes found indoors on walls, windows, screens, doors, etc. (Some are carried indoors on firewood.) They depend on their vision (keenest of all spiders) and leaping ability to catch prey, especially flies. Two of their 8 eyes are very large on the face and eye color can be changed as needed. After mating, the female constructs a silk cocoon for her eggs and guards it. Some can bite humans.
These spiders are about 1/2 inch or less, can walk forward, backward or sideways, holding their legs crab-like. The body is compressed (top to bottom), short and broad with the first 2 pair of legs larger than the last 2 pairs. Many have horns or ornaments on the head or abdomen, and some mimic bird droppings. Males are smaller than females and have much longer legs. Those that inhabit trees or hunt on the ground are usually colored in shades of gray, brown or black, while those that frequent flowers are brightly colored in red, yellow, orange, white and/or green. These spiders mimic the colors of the flowers upon which they rest to ambush their prey. Some alter their color to match the background. They apparently have a toxin potent to bees, flies and other insects larger than themselves. They do not make webs, but females lay their eggs in a sac and die before the eggs hatch.
Both the black widow spider and northern widow spider are present in Ohio. The black widow spider is found primarily in the southern Ohio counties whereas the northern widow spider is found in the northern Ohio counties. Most occur outdoors and are not aggressive unless confined or disturbed. Females are more likely to bite when guarding an egg sac. Reports indicate that mortality from bites is the result of 1% or less of the cases, usually occurring in very young or very old individuals. With healthy people, recovery is usually complete in 2-5 days. However, this spider is considered the most venomous spider in North America.
Adult black widow spiders have shiny, jet black, rounded, globular abdomens with 2 reddish or yellowish triangles on the underside that form a characteristic hourglass marking. Adult female northern widow spiders are shiny black or brown-black with 2 reddish triangles on the underside, resembling a split hourglass. These spiders are about 1/2 inch long, not including the legs (about 1-1/2 inches when legs are spread). Adult males are harmless, about half the female's size, with smaller bodies, longer legs and usually have yellow and red bands and spots over the back as do the immature stages. Newly hatched spiderlings are predominately white or yellowish-white, gradually acquiring more black and varying amounts of red and white with each molt. Juveniles of both sexes resemble the male and are harmless.
Over the past few years, tarantulas have become acceptable pets now widely sold, traded and kept in houses, apartments, schools and dormitories. Occasionally, these very large, hairy spiders escape within a dwelling causing alarm and panic among those fearing spiders. Actually, most tarantulas are docile, non-aggressive and rarely bite. Bites are not considered dangerous and cause little lasting pain. Bites are no more painful than a bee sting, and its symptoms should be treated similarly. Some have a dense covering of special hairs on the abdomen, which, when dislodged, cause skin irritation. This irritation is mechanical rather than chemical in nature.
The name tarantula has unfortunately become associated with several spider families, but most often is applied to the ones called the hairy mygalmorphs. Tarantulas have been much publicized in horror shows in movie houses and television shows due to their forbidding hairy appearance.The largest tarantulas are tropical with a body length of 3-1/2 inches and a leg span of 9-1/2 inches. The largest United States' species has a body length of 2 inches and leg span of about 6 inches. These spiders are stout-bodied and covered with hollow, needle-like barbed hairs, especially on the abdomen. When disturbed, the hind legs are used to scrape off and throw very fine (fiberglass-like) abdominal hairs in the direction of danger, resulting in a remaining bald spot. A bald spot may also occur on the abdomen prior to the shedding of the skin. Hairs may cause a skin rash, allergic reaction and possibly anaphylactic (severe and sometimes fatal) shock to certain individuals.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868
