Why Bites Itch So Much


Posted on Jan 12, 2021      76


 

Oh, this long squeak above the ear - both during the day and at night meeting with a small arthropod from the order of the two-winged mosquito brings nothing but irritation. And both emotional and physical irritation. And now a picnic is not in pleasure, and your sleep is not like that of a baby, you just have time to pat yourself on one place while you are desperately scratching the other - without this second relief life is not the same anymore.

Imagine that you are a mosquito, and you urgently need to satisfy your blood hunger. True, even if you are male, imagine yourself as a female mosquito, because the males of these arthropods are true vegans and eat only the nectar and juice of plants. Blood is a source of more concentrated and useful nutrients, such as lipids, and its most important value in the diet of mosquitoes is getting proteins as a building material for the production of eggs, i.e., offspring.

As a hungry female mosquito, eager to produce many offspring, you see the prey in several ways. First, the mosquito reacts to an excess of carbon dioxide, which all warm-blooded animals, including you and me, actively exhale. Let’s call this system early detection. Next, the sensors for detecting heat emitted by animals or humans are turned on, and a whole chemical bouquet of lactic acid molecules and other elements. Of the 72 types of olfactory receptors on the mosquito’s antennae, 27 are tuned to detect chemicals emitted by animal and human sweat.

Not all mosquitoes feed on the blood of warm-blooded animals, but only females. Males, like this beauty, prefer plant food as nectar and plant sap.

It’s funny how nature has adapted these bloodsuckers: those receptors, which in other two-wings protect the body from hypothermia, in mosquitoes were transformed into a kind of mosquito thermal imager. Scientists from Harvard could find that this thermal imager is most sensitive in the temperature range from 30 to 37 degrees Celsius. The typical temperature of most warm-blooded animals.

So, you, sorry mosquito, have chosen a place to land and in anticipation of a meal. Before you eat, pierce the skin of the victim. Children have much thinner skin, which is why they are attacked by bloodsuckers more often, but everyone gets it without exception: both children and adults, and other animals with much thicker skin. Their teeth, called maxillae, you pierce the skin, and do it as carefully as possible in order not to get to the nerve endings. With your mandibles, you hold the pierced skin in place like a tailor holds a cloth in one hand while he uses his scissors with the other. Next comes the turn of the labrum, a special probe that identifies a blood vessel under the skin and pierces it. Next, blood through the sting, which is actually a bundle of tubes, blood enters the stomach. The mosquito sucks nothing: the blood itself fills it because of the pressure difference in the blood vessel and in the external environment. In addition, hypopharynx (specific tongue) creates a vacuum on the same principle as an infant sucking the mother’s breast, which additionally contributes to blood withdrawal from the victim.

Parallel to the process of blood withdrawal itself, the clotting protection system works. The mosquito saliva, containing special enzymes - coagulants - that prevent blood from clotting, is directed through the hypopharynx to the puncture site. It is these chemical impostors that trigger an immune response in the human body: a landing force of leukocytes, platelets and antibodies is immediately sent to the place of damage to neutralize the foreign protein. Starts a real war, during which often suffers and the body of the victim which in the “battlefield” formed swelling, redness and the most unbearable itching. Sometimes, mosquito bites cause a serious allergic reaction with fever and severe swelling, which have to be stopped by medication.

In the photo, the female mosquito is so full that it has already dumped the excess food. A sense of proportion? No, I haven’t.

But the mosquito no longer cares: while the victim scratches the place of damage, the insect is looking for a new victim. An interesting fact: female mosquitoes during mating attract the attention of males by a characteristic thin sound resembling a squeak which they create with the help of their wings. Mosquitoes pick up the sound vibrations with their sensitive antennae. The squeak of adolescent females differs from that of older females. Male mosquitoes hear this and opt for mature ladies.


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