What are nits and lice? Features of parasitic insects

Many inconveniences bring nits and lice to a person. The former are insect eggs, known as mammalian parasites. 2 species live on humans and carry infectious diseases: eating exclusively blood, they bite through the skin and blood vessel walls. Due to the structure and other features, lice and nits demonstrate an enviable vitality.

What are lice?

Lice - This is a whole suborder of biting insects. Its Latin name is Anoplura. These are small ectoparasites: they feed on the blood of only one species (less often - on several related) mammals. To do this, they have mouth organs specially adapted for biting their skin and sucking.

The development of lice goes through three stages:

• egg;
• larva;
• adult (adult).

Two species annoy a person: Pediculus humanus and Phthirus pubis (human and pubic louse) The remaining representatives of the detachment are also divided according to the victim on which they can exist. For example, there are rat and pork lice. In total there are about 500 species.

Sometimes you can find information that a person is annoyed by 3 types: head, wardrobe (linen) and pubic. But, from the point of view of biology, this is a fallacy, because the first two are varieties of Pediculus humanus with slight morphological differences.

Description of adults

An adult louse is a small insect whose body length is 0.4–6 mm, depending on the species, so some can only be examined under a microscope. The chest and head of the parasite, clearly separated from each other, are several times smaller than the voluminous abdomen. It has large dimensions, because it plays the role of a kind of tank for drunk blood. After feeding, the louse visually increases in size.

Lice have wings. True, they are reduced (they are too small to fly). Scientists believe that this happened due to a change in the lifestyle of insects to parasitic during evolution.

The insect's mouth apparatus meets the demands of its lifestyle: it is a piercing-sucking type. The base is a tube, on the outer end of which there are hooks clinging to the victim’s skin for stability and close contact. Two sharp stylet in the form of needles are hidden in it. When the insect does not feed, it draws the proboscis into the capsule of the head. Nature also took care of the interesting function of the anterior esophagus of lice: when it is nourished, it contracts and expands, acting as a pump. Thanks to this, the insect absorbs blood.

Insects have no organs of vision, although in some species they are replaced by age spots. Lice do not need eyes: they are oriented in space with the help of short antennae. They capture odors by performing an olfactory function.

Lifestyle

Almost all his life, a louse spends on the body of one owner, only in emergency cases, looking for a new victim. The duration of how many lice live is an average of 38 days. The insect is very sensitive to environmental conditions:

1. The optimum temperature for the life of lice is a mark of 30 ° C.
2. If the thermometer drops to 20 ° C, then they stop reproducing, and at -5 ° C, individuals begin to die.
3. When the temperature rises to 50 ° C, the insect will die within half an hour.
4. Parasites prefer high humidity - about 80%.

You should also pay attention to the question of interest to many, how many lice live outside a person. Having lost the power source, the insect soon dies: it usually takes 2 days, although the most tenacious individuals can last up to 10 days.

On the human body, lice choose the warmest and most secluded places. The linen variety usually hides in the neck or in the armpits, and the head - in the neck and behind the ears.

Head louse They live exclusively on the scalp and never move to other parts of the body. This feature is associated with the structure of its legs. They are only suitable for moving around round hair. If you look at the incision of hair growing on the body, it will be triangular.

The closest relative is clothes or linen louse. It moves to the human body only during nutrition. The rest of the life and laying of eggs takes place in clothes, for which the variety got its name. None of the types of lice that live on humans live in bedding, towels and other household items. They can leave their owner only by negligence. If soon the parasite does not find a new suitable victim, then he dies.

Breeding

The life cycle of lice, despite its short duration, is quite interesting. Insects are characterized by sexual reproduction, which takes place in three stages:

1. Mating of male and female. The female is ready to enter into contact with males already 2 hours after emergence from the larva.
2. Ovum fertilization. These parasites have an extremely curious feature: it is enough for the female to meet the male only once, so that she can later lay her eggs. Semen is stored inside her abdomen. Therefore, despite the short life span of lice, their livestock on the carrier’s body is rapidly increasing.
3. Egg-laying, the common name for which is nits. Depending on the species, the female makes a masonry either in the victim's hair or in the folds of his underwear.

Reproduction requires active feeding of females with blood. Reproduction is not possible if the ambient temperature is less than 21 ° C and higher than 37 ° C. The term of development of the embryos inside the eggs also depends on this indicator. If it is about 36 ° C, then the larvae will be born after 4–8 days. When the temperature holds around 23 ° C, the development process can take up to 16 days. When lowering to 22 ° C and increasing to 40 ° C, the larvae do not hatch from the eggs.

The survivability of the lice population is also explained by how many eggs the louse lays: from several tens to several hundred in prolific species.

Food

Lice - an insect with an intensive diet. For 24 hours they “feed” more than 10 times, and for each “meal” the individual absorbs approximately 0.5 ml of blood. The process of blood sucking, made possible by the special structure of the oral apparatus, takes place in several stages:

1. From the proboscis, located at the end of the head of the louse, two sharp styletes appear in the form of needles, which pierce the upper layer of the skin. Such knives are mutable parts of the lower lip and upper jaw.
2. From the folds that surround the proboscis tube, when it turns out, process hooks appear. With their help, the insect's oral apparatus adheres tightly to the victim's skin.
3. Through a hole made, a louse injects saliva into the skin, produced in abundance by the glands. It contains coagulants, with the introduction of which the blood ceases to coagulate and, therefore, the wound does not tighten.
4. Alternately contracting and expanding the esophagus tube, blood is drawn from the capillaries into the abdomen of the insect.

The only substance suitable for feeding lice is the blood of warm-blooded animals. No other organic particles of the body - for example, hair or dead skin flakes - can be swallowed by their mouth apparatus. But the closest relatives of lice are capable of this: lice-eaters and lice-eaters, which sometimes causes confusion.

Nits and Nymphs

Nits are lice eggs from which the next stage of development of the insect, the nymph, appears. They have an oval shape. Embryos are reliably protected from adverse environmental conditions by a dense shell with a yellowish tint.

For development to be successful, there must be a suitable temperature and humidity, otherwise the embryos in the eggs die. On the human body, the conditions are almost perfect, while outside of his nits die. The eggs are firmly attached to the hairs and fibers of the clothes with the help of an adhesive substance secreted in the special glands of the female during the laying of eggs.

Harm to a person

Sensitivity to bites of blood-sucking parasites varies in humans due to the characteristics of the body. But in most lice skin punctures cause unpleasant symptoms, therefore, the fact of carriage of insects is usually noticeable immediately. This can also be guessed from the points of dried blood found on the pillowcase (in the presence of head lice) and underwear (when the clothes were wound on the body). Pubic lice cause discomfort in the genital area.

It is not so easy to deal with lice: they are very firmly attached to the hair in their habitat, as well as to the fabric of clothing. Therefore, just shaking off and washing your hair will not be enough.

Lice are dangerous parasites in humans. Their harm is caused by several consequences of infection:

1. Their presence causes disgust, disgust and irritation.
2. If you look at the place of the bite under the increase, then a pigment spot will be noticeable on the skin. To the naked eye, it may appear to be a small brown dot. The bite acquires such a color due to the breakdown of hemoglobin, which remains in the upper layers of the skin after being pierced with sharp insect stylets, which causes microscopic hemorrhage. Such marks are a cosmetic defect.
3. If lice have been living on the human body for a long time, then the affected areas of the skin become rough to the touch and thickened. This happens because the tissue is constantly regenerated after damage caused by parasites, and a scarring process occurs.
4. Substances that make up the lice saliva cause severe itching and local redness. Because of this, numerous scratches appear on the body. Their foci can merge with each other, forming vast areas of damage.
5. Both the combed areas and the bites themselves act as an entrance gate to the human body of pathogenic microorganisms - bacteria and fungi that cause infectious processes.
6. Running cases are fraught with severe skin diseases. At the site of combing, multiple pustules and boils are formed, requiring treatment with antibacterial agents. A strong inflammatory process occurs, which is accompanied by redness and pain.

Therefore, if a person has lice, it is required to immediately begin their destruction. The danger of infection lies in the fact that insects are easily transmitted to others through personal contact and sharing of household items.

Infection with human lice (Pediculus humanus) is called pediculosis in the language of medicine, and pubic (Phthirus pubis) is called phthyroidism. The latter disease is dangerously less due to the small outbreak of the parasite - it lives in the groin and pelvis.

Another aspect of the harm of lice to humans is the ability of parasites to spread infectious diseases. Their body acts as a kind of reservoir for pathogenic microbes, causing dangerous ailments:

• relapsing fever;
• Volyn fever;
• rat typhus;
• relapsing fever.

A century ago, these diseases caused entire epidemics. A key factor in their distribution is unsanitary conditions in which lice are actively transmitted from person to person. Therefore, massive outbreaks of disease associated with parasites were observed during the war and the plight of the population: during hunger or natural disasters.

All these ailments are dangerous to the human body. With them, damage to the cardiovascular and nervous systems, as well as other organs. Earlier, typhoid infection meant a high probability of death, but with the use of antibiotics, the chances of a favorable outcome increase many times over.

History of lice neighborhood

The origin of lice is inextricably linked with the history of mankind. They constantly accompanied people. At the same time, attitudes towards parasites have changed throughout history. If now they cause disgust and association with social disadvantage, then a few centuries ago the attitude to these blood-sucking insects was much more loyal. The recognition of their dangers was promoted by mass deaths due to typhoid epidemics.

According to Slavic beliefs, to see lice in a dream on your body is money. Moreover, the more parasites there are, the more people will receive wealth.

Quite wild for the understanding of modern man, the idea of ​​lice existed in the Middle Ages in Europe. The insect was called the “Pearl of God” because there was “Christian blood” in its abdomen. Being the owner of the parasites was considered a good form, and not to wash throughout life - a sign of holiness and good behavior. All this, of course, contributed to the widespread infection with lice. The poet from Italy, Giambattista Marino, in his love lyrics trembled with awe the insects that live in the light curls of his lady's heart.

Ways to deal with lice

The key is hygiene. You need to try not to use other people's towels, combs and other personal items.

The struggle with lice is complicated by the fact that their nits have a reliable protective shell. Traditional medicines for pediculosis - shampoos and emulsions - are not always able to poison the eggs of the parasite. Therefore, repeated use will be required until complete disposal of insects occurs.

To this day, folk remedies are widely used. They include the use of herbal ingredients (for example, black cumin) and substances that aggressively affect insects: for example, vinegar and kerosene. But the easiest and fastest “popular” way to get rid of lice is to dye your hair with a paint containing hydrogen peroxide, covering them with a plastic bag applied with the chemical composition.

You can get lice everywhere. Therefore, everyone needs to know what these parasites and their nits look like. Finding them at home or loved ones, you should immediately take radical measures to destroy blood-sucking insects and eggs.