|Mosquitoes: A Rogue's Gallery|
Mosquitoes are vector agents that carry disease-causing viruses, bacteria, and parasites
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Asian Tiger Mosquito, Aedes albopictus
Mosquitoes have four distinct life stages, with the first three stages of Culiseta (egg-larva-pupa) being spent in the water. An adult female lays about 150-200 eggs in clusters called rafts, which float on the surface of the water until they hatch in about two days. The eggs hatch into larvae (wigglers), which then feed on small organic particles and microorganisms in the water. About 10 days are required for larval development. At the end of the larval stage, the mosquito molts and becomes the aquatic pupa (tumbler). The pupa is active only if disturbed, for this is the "resting" stage where the larval form is transformed into the adult. This takes about two days during which time feeding does not occur. When the transformation is completed, the new adult splits the pupal skin and emerges.
Females feed primarily on fowl and domestic animals but on occasion will bite humans. Due to the limited flight range of this mosquito, most breeding sites are located near the area of complaints. Males do not bite, but feed on nectar and plant juices. Culiseta incidens is primarily a domestic nuisance and in some regions is considered relatively unimportant as a human pest. Successful laboratory experimental transmission of St. Louis Encephalitis (SLE), Western Equine Encephalitis (WEE) and Japanese B Encephalitis (JBE) virus does indicate a potential medical importance for this mosquito.
|A mosquito's proboscis consists of six parts: two pairs of sharp, flexible serrated blades and sharp-tipped knives, used to cut the hole in skin into which the whole apparatus is inserted, and two very fine tubes; one for injecting an anticoagulant into the wound, and the other for sucking blood into the mosquito's body. You can see an excellent electron micrograph of the proboscis tip HERE.|
Mosquitoes are a vector agent that carries disease-causing viruses and parasites from person to person without catching the disease themselves. Female mosquitoes suck blood from people and other animals as part of their eating and reproductive habits. The female mosquito that bites an infected person and then bites an uninfected person might leave traces of virus or parasite from the infected person's blood. The infected blood is injected through, or on, the "dirty" proboscis into the uninfected person's blood and the disease is thus spread from person to person. When a mosquito bites, she also injects saliva and anti-coagulants into the blood which may also contain disease-causing viruses or other parasites. This cycle can be interrupted by killing the mosquitoes (actually, it's more efficient to kill their larvae before they become airborne), isolating infected people from all mosquitoes while they are infectious or vaccinating the exposed population. All three techniques have been used, often in combination, to control mosquito transmitted diseases. Window screens, introduced in the 1880s, were called "the most humane contribution the 19th century made to the preservation of sanity and good temper."
Mosquitoes are estimated to transmit disease to more than 70 million people annually in Africa, South America, Central America, Mexico and much of Asia with millions of resulting deaths. In Europe, Russia, Greenland, Canada, the United States, Australia, New Zealand, Japan and other temperate and developed countries, mosquito bites are now mostly an irritating nuisance; but still cause some deaths each year.
Historically, before mosquito transmitted diseases were brought under control, they caused tens of thousands of deaths in these countries and hundreds of thousands of infections. Mosquitoes were shown to be the method by which yellow fever and malaria were transmitted from person to person by Walter Reed, William C. Gorgas and associates in the U.S. Army Medical Corps first in Cuba and then around the Panama Canal in the early 1900s. Since then other diseases have been shown to be transmitted the same way.
Flies of North America - Order Diptera. Flies are prevalent in virtually all habitats, with over 16,000 species in North America. Flies can be distinguished from all other insects in that they only have one pair of normal wings. The other pair has evolved into small ball-like structures called halteres, thought to be used as stabilizing organs during flight. Most flies have compound eyes and mouthparts adapted for piercing, lapping or sucking fluids.
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