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Essay/Term paper: Black widow spiders

Essay, term paper, research paper:  Medicine

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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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