Реферат: Black Widow Spiders Essay Research Paper Adult

Black Widow Spiders Essay, Research Paper

Adult black widow spiders have a shiny, black, rounded, circular abdomen and

are about 1/3 inch long (about 1-1/2 inches when their legs are spread).

Adult spiders have two reddish or yellowish triangles on their bottom which

looks like an hourglass marking, and their body color is dark colored usually

black or sometimes dark brown. They are usually recognized because of their

red or red-orange hourglass design on the bottom of their abdomen. This

pattern is changeable and may look like two separated spots. In some spiders

there is no pattern on the abdomen. The immature stages of both sexes of the

widow spiders have red or red-orange or yellow spots and strips on the top

of their abdomen. Females are colored gray or pale brown. Their color gets

darker as they get older. The hourglass pattern on the underside of the

abdomen forms throughout their development. Male widow spiders are smaller

about 1/4 inch long, and they’re usually not black in overall color, instead

it looks like a light brown or gray. Male widows have an hourglass pattern

too. When they are full-grown they have large knob-like shapes called

pedipalps, which start from the head. But to females they still look the

same. Newly hatched spiderlings are white or a yellowish-white, eventually

turning blackish when they get older. Adolescents of both sexes look like

the male.

Black Widow spiders build loose and uneven mesh-type webs of rough silk in

dark places usually outdoors. And build their webs near the ground

(sometimes inside of houses) but mainly they build them outside. Black

Widows can be found near the ground in dark undisturbed areas. Nest sites

are near holes made by small animals, or around construction openings and

woodpiles. Also they can be found around low shrubs which are usual sites

for widow spiders. Black widows are also found inside in dark undisturbed

areas like behind furniture or under desks and in undisturbed basement areas

and crawl spaces of homes are areas where black widow nests are. They don’t

produce a web like the weaving spiders do or the funnel pattern webs that the

funnel weaver spider’s make.

The female lays eggs in silken cocoon sacs about 1/2-inch in width. The sack

is a pear shaped, and is a creamy yellow, light gray, or light brown in

color. They usually lay about 300 to 400 eggs per sac and have 4 to 9 egg

sacs made during a summer. But only 1 to 12 young survive after the egg

incubation period of about 14 to 30 days because of cannibalism. Growth

requires 2 to 4 months depending on availability of prey during which the

females shed 6 to 8 times and the males 3 to 6 times. Females mature 92 days

after the egg sac outburst and live for about 179 days, while males mature 71

days after outburst and live for 30 days. Because usually the female eats

the male after they mate. But sometimes if females are well fed, the males

get away to mate for another day. The females hang belly upward and very

rarely leave the web. In cold weather and droughts it can cause these

spiders to go into buildings. Prey caught in the web include a many

different insects (cockroaches, flys, and beetles) and other arthropods. The

female black widow is shy and usually only goes out at night. But when she

leaves her web she usually goes far away from her the web. Outbreaks of

black widows occur off and on. Some years an area may have thousands of

widows and the next year they may be gone. Certain kinds of habitats such as

sand dune areas may have black widows every year. Alternating warm and cold

weather during the winter and spring months are harmful to their survival.

The venom of the black widow spider is 15 times as toxic as the venom of the

prairie rattlesnake. However, only a small amount of the toxin is injected

with a single bite by the spider, while the relatively large amount of

injected rattlesnake venom results in about 15 to 25 percent mortality among

those bitten.

The severity of a person’s reaction to the bite depends on where you were

bitten, amount of venom injected and the depth of bite. When a black widow

spider bits you it injects a toxin that affects the nervous system. At

first, there may be only slight swelling and two faint red spots surrounded

by redness at the bite. Pain may be intense in one to three hours and could

stay for up to 48 hours. Pain usually starts from the bitten limb up or down

the arm or leg and then restrict in the abdomen and back. Also muscle and

chest pain or tightness in those areas are some common reactions to a black

widows toxin. The pain can also spread to the abdomen which causes cramping

and nausea. The abdominal muscles may become stiff and board-like with

severe cramps. There can be pain your muscles and soles of the feet and your

eyelids may become swollen. Other symptoms include restlessness, anxiety,

breathing and speech difficulty, tremors, vomiting and sweating. Swelling

can be noticed in extremities and eyelids but rarely at the place where you

are bit. Also there is a sense of discomfort after you are bitten, and some

symptoms increase in severity during the first day after you are bit. But

symptoms usually get better after two to three days but some mild symptoms

can continue for several weeks after you have recovered.

The bite that is usually the most dangerous a female bite. Although it is

very painful, fatalities from untreated black widow bites are uncommon.

During 1926 to 1943, death ranged from 4 to 5 percent, but current medical

treatments have reduced this to a smaller percentage. Death usually results

from respiratory paralysis. People with a history of high blood pressure are

at the greatest risk. But immediate medical treatment can reduce the danger

from widow bites and has reduced fatalities to very low rates in recent

years. However, this spider is considered the most venomous spider in North


If you are bitten stay calm, get the spider, if you can for positive

identification and because of the possible severity of black widow bites you

should get immediate medical attention is important. If you apply an

antiseptic such as iodine or hydrogen peroxide prevents infection.

Physicians can inject calcium gluconate to help the effects of the toxin so

it is less harmful. This helps support levels of calcium salts that are low

by the effects of a bite. You can also get black widow antiserum. Since the

toxin moves quickly through the body trying to suck out the poison doesn’t

work. People younger than 16 and older than 60, especially those with a

heart condition might have to stay at a hospital.

The black widow spider is shy and usually not aggressive and bites can be

rare even when there are lots of them. The adult female spiders usually stay

in their webs unless they have to because of the temperature or if their web

gets destroyed. They do not search for food and they eat the insects they

get in their webs and are eaten when they get to them. Human bites happen

when the spider is defending their web if it is brushed against or

accidentally pinched. Occasionally, bites occur from hungry widow spiders

when a hand or foot is flopped in front of the nest. Before there was indoor

plumbing bites were usual in outhouses, usually on the males genitals.

To control the problem of black widows check areas in and around your home

where black widows may be found. If you find one it can be killed by

crushing or vacuuming the wed and spider, using protective way. Increasing

the amount of light in dark areas also can discourage spiders. Also

insecticides can work for spider control but it doesn’t control all spiders.

If you do put down insecticide put it in the dark undisturbed areas where

spiders are usually found. Insecticides also can be used to stop spider

migrations into houses by spraying around the outside of the foundation and

lower story windows. Do it before cold weather because that forces spiders

into homes to find protection. The insecticide chlorpyrifos is the most

widely used product to control spiders around the house. Chlorpyrifos remain

effective for several weeks if is not exposed to light and moisture. But

pyrethrin is used specifically for black widow spiders.

To help prevent anyone from getting harmed by black widows, you should tell

everyone in your family to learn about black widows so they can identify and

avoid them. It is also a good idea to wear gloves and a long-sleeved shirt

when working in spider infested areas. Remove trash, old boxes, piles of

lumber, old rubble piles and other unwanted things from under or around

houses and outbuildings. Do not go barefoot or handle firewood without

gloves. Put up screens on doors and windows to prevent them from getting in.

Seal or caulk cracks and crevices where spiders can get in the house. And

wash off the outside of the house or building especially around window wells

and other undisturbed places where they build webs.

There are also several other kinds of widow spiders. I listed them below

and briefly gave you some information. Although there are three distinct

species, they share similar physical and life-history characteristics. The

adult female’s body is usually 0.5 inch long, with a bright red marking

resembling an hourglass on its underside. The male is much smaller, with a

length of .25 inch and about four bright red dot markings on its sides. The

male is shy and rarely seen by humans. The females are generally not

aggressive unless they see a threat or are guarding an egg sac.

All three species of black widow live in close proximity to humans, and each

species shows a distinct preference for not only a specific habitat, but also

its particular nesting area. The eastern black widow, which builds its web

close to the ground, is found primarily in woodsheds and woodpiles, but it

has also been found in parks, especially around the legs of picnic tables.

The western black widow builds its nests higher up and is commonly found in

gardens, especially on bushes, as well as in picnic areas, where it colonizes

the undersides of picnic tables. Although the western black widow is more

commonly found in these somewhat natural areas, the species has also been

discovered in highly urbanized locations. The northern black widow, while

maintaining some proximity to humans, lives generally in undisturbed wooded

areas, as well as around stone walls, trees, and tree stumps, and is almost

never found associated with a house.

The western black widow, Latrodectus hesperus ranges from extreme

southwestern Canada, south into Mexico, and east to west Texas. Hesperus is

the common black widow of the western United States, and it is abundant in

areas of Arizona, California, and other westerly locations. One of the most

commonly places where it is found is in natural habitats for example is in

abandoned rodent holes, but it can also be found around peoples houses, even

in the downtown districts of many western U.S. cities. The western widows

general appearance is very similar to the southern widow it has the hourglass

marking and is usually shaped like a perfect hourglass, but it is divided

into two seperate spots. Like its southern cousin, the western widow it

causes a large number of bites, mostly in the southern locations.

The Northern Widow, Latrodectus variolus, is the third black widow found in

the United States. It is found from extreme southeastern Canada, throughout

the New England states, and south to northern Florida. It prefers undisturbed

wooded areas, stone walls, stumps, and similar habitats. The «hourglass» of

the northern widow is usually divided into two separate, elongate markings.

This species is most common in the northern part of its range. While its

venom is very similar to that of the southern and western widows, and bites

do occur, it does not appear to bite humans as often as those species.

The Red Widow, Latrodectus bishopi, is a U.S. species with a restricted

range, being found only in palmetto fronds of sandy, scrub-pine regions of

central and southern Florida. This spider is rather brightly colored, with

red legs and cephalothorax (fore-part of the body), and a black abdomen with

orange and white markings down the back and sides. The «hourglass» usually

consists a single red elongate marking. Little is known of the bite of the

red widow, but its venom is probably quite toxic to mammals.

The Brown Widow, Latrodectus geometricus, is a cosmotropical species, found

in most tropical seaports around the world; it is an introduced species in

Florida. Coloration may vary, but is usually brown to grey, with white and

black markings on the back and sides of the dorsal abdomen: The «hourglass»

is usually complete. This species is often found on or around human

habitations and other buildings. While definitely venomous to humans, bites

tend to be less severe than those of most other widow spiders.

The Malmignatte or European Black Widow, Latrodectus mactans

tredecimguttatus, is the common widow spider of southern Europe (northern

Mediterranean). It is black, with a series of red markings on the dorsal

abdomen. The malmignatte is a significant medical problem in various parts of

its range. In Herzegovina (the former Yugoslavia) this spider reportedly

causes a large number of bites each autumn in field workers harvesting grain

by hand.

The redback spider, Latrodectus mactans hasselti, is found throughout

Australia, and in some Southeast Asian countries. It is black, with a

distinct red (sometimes pink or light grey) marking on its dorsal abdomen.

Like most widow spiders, it harbors a highly toxic venom, and is considered a

species of clinical significance. Similar species are found in South Africa.

As for if it is currently facing any problems in its environment, no one

knows their exact numbers but they are far from extinction, even if every

spider was killed that was found by a person. And that is my report on the

black widow spider

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