Spiders

Spiders

Myths and a few fatal poisonings have made many persons afraid of spiders. 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. Most are quite beneficial by feeding on harmful insects (flies, crickets, etc.) 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 on House Siding:

Although spiders are quite beneficial, there have been increasing complaints about their webs and fecal specks dirtying home vinyl and aluminum siding. Many insects rest on white colored siding and spiders sit there, waiting for an easy meal not needing to spin a web to help catch and trap its prey. Waiting spiders defecate on the siding, leaving undesirable specks on the paint or other finish. Lighter colors appear to increase spider problems, whereas the insect prey are less attracted to red and black finishes.

Ground or Wolf Spider

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.

Jumping Spider

These common spiders are about 1/2 inch or less, attractive with bright colors often with iridescent scales. They are hairy, stocky 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 eight 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.

Crab Spider

These spiders are about 1/2 inch or less, can walk forward, backward or sideways, holding their legs crablike. The body is compressed (top to bottom), short and broad with the first two pair of legs larger than the last two 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.

Sac Spider

These common spiders, commonly called "two-clawed Hunting Spiders," have been associated with numerous cases of human arachnidism (spider bites). They are suspected of being responsible for most indoor bites. However, deaths have not been reported. Their venom is cytotoxic, mainly affecting tissues at the bite site. These spiders have two claws at the tip of the leg. The venomous species Chiracanthium mildei is light green to yellow white in color with a dark strip on the front portion of the upper-midline of the abdomen. The female body is about 3/4 inch long, whereas the male body is only 1/4 inch long. The long abdomen is slightly flattened. There are eight eyes similar in size arranged in two rows across the front of the face. The jaws are brown and the legs very smooth with the front legs longer than the rear legs. The egg sac is a white paper-like disk, usually placed in a protected area such as under a stone.

The indoor population increases in the autumn as the weather cools and food sources decline. They occur in wall voids or in silken retreats (sacs) constructed in the upper corners of rooms. Sac spiders roam ceilings and walls, seeking prey. When falling to the floor, they rapidly seek a protected place. Outdoors, these hunting spiders do not build webs; but construct a flat tubular sac opened at both ends in a rolled leaf, crevice, under loose bark or stones.

Orb Weaver or Garden Spider

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 produce egg sacs containing several hundred eggs, then die. 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, greenish, etc.).

One common 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) with the front legs sometimes black or with a short band of orange. This spider is about one inch long hanging head down in the center of the web, and found in brambles, bushes, tall grasses, etc., in open, sunny places near human habitations where flying insects blunder into the trap. Egg sacs are spherical, narrowed at one end, up to one inch long and covered with a tough brown, paper-like silk. Despite the formidable appearance of these spiders, they are not considered dangerous, but can bite if handled or molested.

Funnel Weaver

Funnel web spiders are seen most easily in late summer when morning dew makes their webs in lawns conspicuous. Spiders hide at the narrow end of a funnel that spreads across the grass and on feeling the vibration of an insect crossing the web, the spider dashes out, bites the insect and carries it back to the funnel. Some of these large, flat, sheetlike webs occasionally cover shrubs, such as junipers and yews, during the autumn months.

Spiders are about 1/2 inch long or more, variously marked with shades of gray, brown, white, black and dull yellow. Females deposit a disc-shaped egg sac in a crevice, then may die while still clinging to the egg sac. In former times, the silk of this spider was used to cover wounds to stop bleeding.

Cellar or Daddy-Long-Legs Spider

These spiders, about 1/3 inch long with long, slender legs up to two inches long, whitish-yellow to pale gray bodied, are common in barns, cellars and damp warehouses. Eyes are close together. Many hang upside down in a loose web in dark corners of houses or cellars. Males and females live together and when alarmed shake the web violently. The female carries the round egg sac in her jaws.

Harvestman

These tan to brown creatures are not considered spiders, but resemble cellar or daddy-long-legs spiders with an oval, compact body and extremely long, slender legs. They may be found in gardens, outdoor buildings, and occasional homes, feeding on plant juices, dead insects and some live insects.

Fishing or Nursery-Web Spider

These spiders resemble wolf spiders, attracting much attention due to their large size with a leg span of three inches. They may sit quietly for hours, legs spread out on vegetation or boat docks, or they may hunt actively in vegetation. Many can run over the surface of water and, if chased, dive and stay submerged for some time. The female carries her huge egg sac in her jaws under her body. When hatching time is near, leaves are tied together with silk, with the egg sac, among them. She has excellent vision and guards the nearby egg sac. Young spiders leave the nursery about one week later. Many live near lakes and streams, but occasionally are found indoors in moist areas. They feed on aquatic insects and even small fish.

Control Measures

Try to determine if the spiders are of the indoor or outdoor type and whether they produce webs. Most spiders that live indoors are small (usually 1/4 inch long), uniformly pale yellow, tan or gray, and not hairy. Spiders that live outdoors and accidentally invade the house are usually large (1/2 inch or more), hairy, and distinctly patterned (some bright colored). They commonly run, jump or move rapidly.

Prevention

Sanitation is critical in successful spider control. Collect and destroy spider webs, egg sacs and spiders with a strong suction vacuum cleaner with proper attachments to reach the necessary places. Use a dust mop, stiff broom and dustpan when needed to help discourage establishment. 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 cockroaches, which attract spiders. Be sure to control excess moisture and humidity, keeping basements, crawl spaces, porches, etc., as dry as possible. Also, clean up woodpiles, trash, rocks, compost piles, old boards and other debris outdoors, especially around the house foundation where spiders 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 from outdoors. 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.

Identification:

Spiders have eight legs (four pairs), vary in size, shape and color, and lack wings and antennae. Their body regions consist of two parts; 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 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.

Life Cycle and Habits:

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 (three weeks or the following spring) and 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. 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, 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. House or Cobweb Spider The female house spider is larger than the male, about 1/3 inch long, gray to brown with the rounded, globular abdomen mottled with several dark stripes on the upper side (Black Widow Spider shape). House spiders spin their webs in dark corners of moist rooms and outdoors. They hang upside down in the center of an irregular cobweb. The outside sticky threads entangle many insects, especially flies which are bitten and sucked dry. Females are fertilized several times during a lifetime with 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. They are cannibalistic, eating one another. Spiderlings take several months to mature. Webs become dust covered when abandoned