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Posted 2003-07-14, 06:57 PM
in reply to Arbitus's post "Good Bye"
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How Mosquitoes Find Us
Mosquitoes use visual, thermal, and olfactory stimuli to locate a host. Of these, olfactory cues are probably most important. For mosquitoes that feed during the daytime, movement of the host and the wearing of dark-colored clothing may initiate orientation toward a person. Visual cues seem to be important for in-flight orientation, particularly over long ranges, whereas olfactory stimuli become more important as a mosquito nears its host.
Using sensors on its antennae, a mosquito picks up animals' body heat, odor and carbon dioxide from exhaled breath. The female mosquito follows the trail upwind to its source. Once mosquitoes get closer, they're attracted to other cues such as dark colors, moisture in the air, and silhouettes of potential victims. British researchers found that mosquitoes responded to the body cues of an animal standing 45 feet away.
One of the most authoritative sources of information on the subject is an article by R. H. Wright in the July 1975 issue of Scientific American. According to Dr. Wright, the female mosquito (only the female feeds on blood--the males prefer plant juices) tracks its quarry by a "sniffing" mechanism which monitors heat, moisture and carbon dioxide content in the air. If a mosquito is downwind from a creature (such as a human) who emits these qualities, it will zig-zag upstream in the air flow until it finds the source. Mosquitoes do not have very good long range vision, and sight is not really a factor; but even if it were, the insect does not have the brains to distinguish between an animate and an inanimate object on the basis of sight alone. This is why we observe most mosquito "clouds" lying downwind from us. If a mosquito should wander out of the air flow passing our bodies, we have effectively eluded it, and it must start over again.
This is why mosquito repellents work. It is not that they smell bad to the insect--it is because the molecules which they contain block the sensing mechanisms that the mosquito carries in its antennae to detect heat, moisture and carbon dioxide. In other words, if an effective repellent is in the air, the mosquito gets lost on its track to the target.
Mosquitoes do not become active until temperatures reach about 45 F. Some research found that mosquito activity increased with increasing temperature to about 68 degrees. Above 68, mosquitoes become less active, and the pests take cover at the upper threshold temperature of about 82 degrees. Wind speed higher than six meters a second will ground mosquitoes.
How Mosquitoes Bite
Mosquitoes feed through a flexible tube made up of six highly specialized mouth parts. Two of them are serrated at the tip and saw back and forth to cut tissue. The tube has extremely sensitive chemical sensors to detect molecules in blood so the mosquito knows when she's hit a pay streak, so to speak.
The itching and swelling a mosquito bite is from our bodies allergic reaction to proteins in the mosquito's saliva, which serves an an anticoagulant. She injects it continuously while probing for or drinking blood. The injected saliva is what transmits mosquito borne diseases.
A feeding mosquito will suck up about one millionth of a gallon of blood. That doesn't sound like much, but it may amount to four times her original weight. Her abdomen distends enormously from the bulk of this huge meal. Stretch receptors in her bulging abdomen send flunk signals to her dot sized brain, which tells her to disengage and get away. This is a physical mechanism, and simply reflexive. Determined and possibly vengeful scientists observed that when the connection between their stretch receptors and brain is cut, mosquitoes would feed until they burst.
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. Hope you'll become fully healthy.
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