Head louse: development cycle, speed and characteristics of reproduction in humans

Hello! I am ashamed to admit, but as a teenager I managed to pick up lice somewhere.

Even my mother was afraid to say at first. But the problem had to be solved. Of the whole period, I most remember the visit to the doctor.

Of course, they promptly helped me, but before that I had to listen to a peculiar cycle of lectures about the head louse, its development cycle, and optimal methods of elimination. For the rest of my life, I remembered all this, so now I will share with you, friends, useful information.

Lice development cycle

Everyone knows that on the human body there are three types of lice: head, body and pubic. Each of these species has its own specific features, however, in general, the reproduction and development of all types of lice is the same and differs only in small details.

It is no secret that the development and reproduction of head lice is very rapid. So, just sixteen days after the egg was laid by a sexually mature female, the louse that hatched and developed from it can lay its own eggs.

It is in connection with such rapid developmental periods that already a month after infection with head lice, an incredible amount of insects and nits can appear on a human head without appropriate treatment.

The full life span of lice is 32-42 days. Moreover, during this time, the head louse manages to lay from 80 to 140 eggs, the pubic louse lays about 50 eggs, the body louse can lay as many as 300 eggs.

As a rule, the whole life of the head louse takes place on the same human head, but there are cases of the transfer of lice to the head of another person in case of close contact, as well as in some other situations, which just leads to infection with head lice.

The entire development cycle of lice can be noted as nits - larva - nymph of the first age - nymph of the second age - nymph of the third age - adult louse. After each molt, the nymph moves from one age to another.

The need for molting is that during the growth of soft tissues of the nymph, the growth of chitinous cover is absent and it is periodically necessary to change it. The entire molting process lasts around five minutes, and after forty-five minutes, the new cover becomes denser and the nymph can begin to feed.

After the last molt, the larva, having turned into an adult female louse, begins to mate and lay eggs already during the first and second days, attaching them near the root of the hairs.While still in the sex glands of lice, the egg is coated with a special sticky secret with which it then leaves the oviduct.

Nits are very small in size, which makes them difficult to detect. In addition, they are often confused with dandruff due to the great similarity in color and shape. However, dandruff is easily removed from hair, unlike nits.

The development period of nits under suitable conditions is from 5 to 8 days, after which a larva of the first age appears from it. In just one or three days, such a larva turns into a nymph of the first age after it is first saturated with human blood and passes the first molt.

Moreover, the lack of food in such insects as lice is not due to their stay just at the source of their nutrition. Due to this fact, as a rule, there are no delays in the development of head lice.

As for the larva, it differs from the adult individual only in the smaller size and weak development of the reproductive system. The optimal conditions for the development of nits and lice are considered to be temperatures in the region of 30-31 degrees Celsius, which usually corresponds to the temporal and occipital parts of the human head.

When the temperature differs from the indicated interval, the development of nits slows down until it stops completely, which is typical for temperatures outside 22 and 45 degrees Celsius.

It is also worth noting a certain feature of the process of emergence of a larva from an egg. The fact is that the larva, even after piercing the egg shell with the jaws, still cannot get out of it onto the surface of the head.

In this regard, in order to get out of the egg, the larvae have a very interesting way: they begin to breathe actively, so that air passes through the entire digestive tract and leaves in the anus, after which, having accumulated at the bottom of the shell, it simply pushes the larva out.

Moreover, it is very interesting that when a larva is born, it does not have any sexual characteristics and only later becomes a female or male, depending on which insects of which sex are not enough.

Thus, knowing the features of the period of development of lice from an egg to an adult, it is possible to predict the course of a disease such as pediculosis, as well as the possibility of its treatment.

Lice and nits: incubation period, treatment (time for reprocessing)

From the moment of the first meeting with lice and until the onset of the first symptoms, 30 days can pass, sometimes more. Therefore, you can imagine how many lice already run on the skin, remembering where and when the infection could occur.

Personal hygiene of an already infected person does not affect the rate of reproduction of lice. The higher the temperature (from 30 degrees) and the greater the humidity, the faster the reproduction of lice.

In the absence of contact with the body in the external environment at temperatures above 40 degrees and below 20 degrees, further development does not occur. Outside the body, head lice live for no more than 2 days, and body temperature always coincides with the “comfort zone” of the insect.

By the phrase “incubation period” we mean the time from the moment of infection to the first symptoms. There is still a biological understanding of this term. Then we are talking about the development of lice eggs, that is, nits.This is the time interval during which the conversion of lice from nits occurs.

How lice caused by lice Pediculus humanus capitis is transmitted

Lice are insects that are “devoted” only to humans. Therefore, you can get infected only from a person with a pediculosis. Do not listen to the legends that lice can live on pets for some time. They have their own lice.

Lice do not know how to jump and fly. Therefore, infection is possible only with close contact at a short distance, when there is the possibility of crawling. As they say "head to head." By the way, lice have excellent dexterity when crawling.

If we talk about nits, then they are motionless. But they can get to a healthy person from a patient through hygiene items and personal items (comb, hat, towel, pillow, etc.)

How are they infected with head lice?

Places of infection can be different: school, kindergarten, camp, public transport, hotels, hospitals, hairdressers, trains and other popular places for the population.

For infection, a suitable place is necessary (the options are given above) and two people who have been in contact for some time, one of whom has pediculosis.

How can you become infected with lice: you can get infected only through direct contact. Being in different corners of the same room with a person with a pediculosis, a healthy person will still remain healthy.

Children often reward each other with head lice. Pubic pediculosis can be acquired with frequent changes in sexual partners and indiscriminate sexual relationships. In children, pubic louse can settle on the head and eyelashes.

Pubic louse in children is usually a “criminal” sign - a symbol of the child’s sexual use. The body louse most often settles with the homeless.

How quickly do parasites multiply on the head?

There is nothing to console in this matter. Lice breed fast enough, even rapidly. One louse per day lays an average of 5-10 eggs (nits), which, depending on temperature and humidity, turn into ordinary lice after 3-4 weeks, which can also lay eggs.

How do lice breed on the head: as soon as an adult lice managed to cross over to the head untouched by its tribesmen, it does everything possible to provide the owner with a new population of lice, the louse eats and lays eggs (nits) when fed.

Lice Life Cycle Pediculus humanus capitis

From the moment of its inception to the very death of Pediculus capitis, 4 stages of development pass: egg (nits), larva, nymph, adult.

An egg from the oviduct is removed in a sticky lubricant, which forms the shell of the nits. Later, this capsule-shaped lubricant hardens already on the hair, and firmly holds the nits in place. The capsule protects developing lice.

It is very interesting that the larva exits the egg. The shell of the nits is dense enough, and to overcome this shell, it must be pierced. This is what larvae do by piercing one end of this cocoon with their jaws.

The louse's appetite is very good and they eat every 2-4 hours. In order to actively multiply, they need strength. They do not have hunger strikes, as there is no problem finding food. Food is always there. When the larva emerged from the shell of the nits, it was already a nymph.

The nymph molt two more times to turn into an adult - a mature individual. Shedding is necessary because the cocoon in which the larva lives does not grow. And the nymph needs protection from adverse environmental factors and drug shampoos.As the larva grows, it needs to change its protective “clothes”.

A sexually mature louse can only mate after the first bite. Two days later, the female lays eggs, then eggs are laid every day, a maximum of 10 pieces.

If we briefly describe the reproduction and development of lice in terms of time, then it will look like this:

1. the incubation period is from 16 days to 30 days;
2. a week is needed for the maturation of nits;
3. the larva develops for 1-2 days;
4. the nymph develops 5 days before the first molt (nymph of the first age) and the development of the nymph lasts 7-8 days until the second molt (nymph of the second age);
5. an adult insect (adult) begins to mate 1-2 days after being transformed from a nymph. A mature louse lays eggs every day.

We can say that on average, 20-21 days pass so that louse appears from the nits.

Treatment

Now that you know how lice become infected, how lice breed on the head, how many nits an adult spawns in a day, and after what time the young hatch from nits, it will be clear why the treatment should be repeated several times. There are many medications aimed at inhibiting the life of insects or their destruction.

All remedies for lice can be divided into those that kill only living individuals, and those that also kill nits (drugs for pediculosis - pediculocides with ovocidal activity).

Folk methods of combating pediculosis exist no less. Read more about pharmaceutical preparations here, and about folk remedies against lice.

Most drugs are NOT EFFECTIVE against nits and therefore a head re-treatment is required. Niticide killers contain MALATHION.

In the presence of any chronic diseases, as well as in the treatment of children under two years of age, it is better to consult a doctor for the correct selection of medication.

Now that you know how lice become infected, how lice breed on the head, how many nits an adult lays on a day, and after how long the hatchlings hatch from nits, it will be clear why treatment should be repeated several times.

An interval of 7 days is necessary to consolidate the effect. If after the first treatment some nits manage to survive, then the larvae hatching in a week can “start” the process from the very beginning.

In order not to meet pediculosis without saying goodbye, a week after the first treatment procedure it is necessary to repeat the “session” of treating the head with the chosen remedy.

Breeding lice. The lice reproductive cycle

Lice are dioecious, but hermaphroditic individuals (Nuttall and Keilin) ​​are found in the crosses between the head and body lice. In appearance, male lice are well distinguishable from females, primarily in their smaller sizes. The rear end of the male’s body is rounded, while the female’s is bifurcated.

The genitals of the male consist of two pairs of saccular testes, seminal ducts, adnexal glands, the ejaculatory canal and the copulative organ with its parts. The sexual opening of the male is shifted up and lies behind the anal opening.

The female reproductive organs are formed by two five-tubular ovaries, two short oviducts, an unpaired oviduct with a uterine sac, a receptacle, glue glands and a vagina.

Mating lasts 20-40-70 minutes. It can be done at any time.The female is able to copy immediately after the last molt, and the male - only a few hours after it. The mating of the worm entered valid for 15-20 days, the head - for 7-12 days.

Fertilization in lice is internal. Mature nits are squeezed through the oviducts into an unpaired excretory sleeve, and, like a piston of a syringe, pushes the secret of highly developed adhesive glands in front of them.

Before laying, the female head louse moves briskly. Choosing a suitable place, she grabs a gonopod hair or thread and stops. A drop of transparent secretion of glue glands protrudes from the genital opening, which covers the hair.

After a few seconds, the louse creeps forward, and the nit is already glued to the substrate. The egg laying process lasts about 17 seconds. The glue secret in the hardened state is very strong and resistant to various chemicals. With caustic reagents, it is possible to ruin the very hair on which the nits sit, rather than dissolve its glue.

A well-fed female can lay eggs without fertilization, but nothing is hatched from them. Not all eggs laid by a fertilized female produce larvae. Of 1158 eggs kept at + 30 °, about 70% of larvae hatched (Nuttall); the remaining eggs were either not fertilized, or in them the embryos died during their development.

Bacot observed the laying of 91–97% of fertilized eggs. Obviously, in this regard, large fluctuations are possible in some cases. The most important conditions for egg laying are: plentiful nutrition and temperature not lower than + 20 ° and not higher than + 37 °. The optimum for masonry is about + 32 °.

In one experiment, 65 female body lice at + 22 ° C laid three eggs in two days; 35 of these females were transferred to a thermostat at + 30 °; here, lice gave 188 nits per day. A body louse puts 6–11–14 nits on a day, and not more than 295 in its entire life. The head louse gives no more than 4 per day, and no more than 141 nits per day.

The nits of various human lice are somewhat different from each other. There is no doubt that the plots are isolated in this respect: their nits are pear-shaped, 0.65-0.67 mm long, with a high domed lid. Body lice and head lice in extreme forms of nits also differ from each other.

The head louse egg is oval with a slightly convex and moderately high lid; its length is 0.75-0.8 mm; sticks to one hair, not to cross them.

However, these signs, apparently, do not in all cases make it possible to accurately distinguish between the nits of head and body lice, since, due to variability, their extreme variants are found on top of each other. The question needs further research.

Conditions for breeding lice. General biological data

At temperatures below + 22 ° and above 40–45 °, hatching of larvae from rnids does not happen (Nuttall). Alternating cooling slows down the development of lice. In periodically removed and worn dress development lasts up to 6 weeks. Optimum development of 30-31 °.

In indelible clothing, the larvae emerge from the nits after 7-10 days. Shorter than 4 days, fetal development of body lice cannot be (Nuttall).

From a review of these data, we are convinced of the delaying effect of dryness on the development of lice. Of head lice nits at + 32–35 °, the largest number of larvae leaves on the 7th day; Yet development lasts from 5 to 9 days.

Nits can withstand 10 minutes immersion in kerosene, gasoline and ether without harm to themselves; A 2.5% solution of carbolic acid kills them in 10 minutes, 2% lysol in 5 minutes, sublimate vinegar and glycerin in 1-2 minutes.

The procedure for dropping the skin lasts about 5 minutes; after 3/4 hours, the young skin becomes denser, and the louse can already suck blood.

General biological data

The full life cycle of pediculus lice consists of the following periods:

• embryonic development under the cover of nits - from 4 days to 6 weeks;
• postembryonic development;
• sexually mature phase.

The life cycle of a body louse - from the moment of laying the eggs to the beginning of laying of the female that left the egg (from egg to egg) - if kept on the human body, it lasts 16 days (Hamer).

In general, body louse can live up to 2 months; the usual norm for the duration of its life cycle, not counting embryonic development, is 5 weeks; the head louse lives about 4 weeks. Toward the end of her life, a female head louse may have 4,160 descendants (children, grandchildren, great-grandchildren, etc.).

The ratio of lice to temperature is characterized by the following data: a 30-minute stay of lice in dry air at 49 ° does not kill them, at 54 it kills in 35 minutes. Air and water at 55 ° kill them in half an hour; the temperature in -12e does not immediately kill the lice, which, from the cold, are primarily numb.

Head Lice Life Cycle

Head louse - a parasite that affects the skin of a person.

Unfortunately, everyone can become infected with head lice. Knowing the symptoms of this disease, it is difficult to confuse it with any other.

More about lice

Few people know that lice do not jump. In addition, they do not know how to fly, so lice are transmitted from person to person either by personal and fairly close contact, or by the common use of clothing, home textiles and personal hygiene items.

If you want to protect yourself from possible lice infestation, protect yourself from unverified contacts with people. But remember: lice are not always transmitted to another person in direct contact with the skin of the infected.

If in a public transport or in another place where at the same time there are many people next to each other, you will notice a suspiciously scratching person - move away from him.

When visiting pools, wear a bathing cap made of rubber on curls. As mentioned earlier, lice do not jump, but they swim beautifully.

Therefore, the risk of infection with head lice while swimming in a pool or in a closed reservoir is quite high. Do not allow anyone to use their comb and towel.

Lice breed fast enough - the development cycle from the larval stage to the adult stage is eight days. They are able to reproduce offspring on the twentieth day of their life.

The lice population feeds on human blood. To get to the blood, lice bite through the skin and leave small but noticeable microranes on it. The first symptoms of the onset of the disease are severe itching on the temples, nape and skin behind the auricles.

If lice are not destroyed within a few days after their appearance, lice begin to proliferate actively, covering new areas of the head with their larvae. Lice have an elongated elongated body, which is equipped with short but tenacious legs, allowing them to quickly move around the skin and hair.

In a hungry state, lice have a silver or amber color. The body of full lice is painted in the color of blood. The temperature that they need for life is thirty-six degrees Celsius and above, and lice die at a temperature of twenty degrees and below.

Thus, the temperature of the skin of a person is ideal for their life. Once outside the skin of a person, lice die quickly.

The development cycle of lice implies their external change. Lice larvae are small in size, which allows them to merge with the hair shafts.

An adult head louse lays eggs called nits, attaching them to the hair roots with the help of a special sticky substance that produces its digestive system. It is impossible to dissolve this natural glue with water, therefore it is pointless to combat the appearance of lice and nits with the usual washing of the head.

Over time, small larvae hatch from the nits, which in their appearance repeat the appearance of adult lice, but differ significantly in size from them.

In the state of larvae, individuals of lice live for at least several days, during which lice grow, receiving energy for development from human blood. On the tenth or twelfth day, lice have a fertile period, during which lice multiply, laying eggs of nits.

The life cycle of lice is thirty days, but during this short time, lice manage to reproduce several offspring, the total amount of which can reach up to three hundred nits.

Manifestation of the disease

After you find out more about the nits development cycle, as well as how many adult lice live, read about signs of head lice damage to the scalp.

Please note that self-diagnosis does not always lead to confirmation of the presence of this disease.

Human skin has a huge number of nerve endings that can cause itching, responding to external or internal stimuli.

The first signs of the appearance of lice, especially when they are in the stage of nits, often coincide with the usual itching of the skin caused by a nervous breakdown of different strengths.

Many people do not know how much time can pass before the lice on the head finally enter the rights of the new owners of hair. On average, this period is seven days, during which the louse will postpone nits, and they will have time to hatch and begin a new stage of their development.

But when the offspring of the parasite is born, it will be impossible to ignore the discomfort from their countless bites.

Dermatologists have an unwritten rule that states: if a sick person contacts other family members or shares one office with colleagues at work, not only the sick person, but also his surroundings should be treated.

Infection may not occur, but it is worth excluding any possibility of the appearance of lice on the heads of other people.

It will become food and an incubator for parasites, supporting the necessary temperature environment, outside of which lice do not live.

Symptoms of the disease

Signs of head lice may be as follows:

These symptoms are quite averaged. People have a different pain threshold.

Some of them immediately find that there are lice on their heads, while others do not perceive their bites for a long time. If you ignore the disease for a long time, you can bring into the bloodstream a purulent infection called pyoderma.

In addition to medications, nits and lice can be eliminated with the help of folk remedies.

Lice treatment

You should not ask questions about why lice appear if they have already settled on your head.

As soon as you find them, immediately visit a doctor or start treatment at home. There are several effective medications that can help you get rid of this problem.

Drugs that fight the manifestations of the disease:

An effective and inexpensive way to combat head lice is Medifox, a photo of which you can find below.

Photos of other tools and instructions for their use can be found on various forums. Do not forget to care for your scalp after treatment.

A radical preparation for treatment is shaving hair in the affected area, which not everyone will agree to.

If there are no curls left on your head, there will be nothing for lice to fasten the clutches of their eggs and nowhere to hide. Lice rarely live in open areas of the skin outside of the hair, so shaving is still an effective method of dealing with lice.

Unfortunately, this method is not suitable for everyone - many ladies, even faced with head lice, are afraid to lose their hairstyle. To remove most nits and lice from the hair without shaving them, you need to apply drugs to the curls that kill the lice and dissolve the composition with which they lay their eggs on the hair.

After you apply a therapeutic compound to the curls, wrap your head in polyethylene. This is an important rule that will allow the drug to work more efficiently.

After combing out lice and nits, you need to take a shower and wash the treatment solution from the head. How many procedures you will need to completely get rid of nits, you can only determine empirically. It is necessary to deal with lice until the signs of their presence disappear.

If you want to deal with lice at home, remember that lice are afraid of kerosene, vinegar or hellebore tincture.

After applying these products, you need to carefully care for your scalp. Such compounds have a strong effect not only on lice and nits, but also on the epidermis, which needs careful restoration.

Care for the scalp that suffered lice should be done with the help of pharmaceuticals, oils or homemade decoctions, as well as other home-made preparations.

Pediculosis is not a sentence. You can get rid of parasites in a fairly short time. The main thing is not to start the problem and not let lice multiply.

How fast are lice on the head?

Some still mistakenly believe that pediculosis, that is, the multiplication of lice on the head, can affect only people who seriously neglect personal hygiene. In fact, a similar situation can happen to anyone, and neither the person’s age or gender, nor his social status or commitment to cleanliness will affect it.

It is not easy to deal with such a problem, as parasites are tenacious, quickly develop and lay offspring. However, if you look at the development cycle of these insects, then it will be a little easier to solve the problem.

Reproduction of lice occurs very quickly. From the moment of laying the egg to the day when the already grown individual lays its own offspring, a little more than two weeks pass. However, such terms are respected if the parasites were not affected by any negative conditions, such as temperature changes.

In the event that something prevented the lice from growing and reproducing normally, the term from egg to egg can be a whole month.As a rule, after thirty days, a huge number of parasites are already on the head, and a little later their presence becomes unbearable. All the symptoms of pediculosis are manifested, which is almost impossible to endure.

It is interesting. The rate of lice development does not differ among representatives of different species and forms. For different types of differences are observed only in some small details.

Of all the existing types of lice on the human body, only two species are able to live - head and body. The second, in addition to the skin itself, live on the patient’s things, often leading to re-infection. However, regardless of the habitat, the life cycle will not have fundamental differences.

The emergence of nits

Lice are among the insects that undergo incomplete transformation. This type implies the absence of a full stage of a typical larva. In most other insects, this period implies the formation of an organism that looks and eats completely differently.

In the life cycle of adult lice, the so-called larval molting period is distinguished. A couple of days after the last of them, the female begins to mate with partners. Just a few hours from the moment of fertilization is enough for the female to begin laying eggs.

Unlike most other insects, lice do not experience hunger. Their food, human blood, is always within walking distance.

Lice do not tolerate hunger. Each individual should be fed at least once every four to five hours. Without food, they die in a few days.

The laid eggs are placed on the hair, while the distance from them to the roots can be different. Future offspring are held in this position due to a special sticky cover. The resulting egg in the shell is called "nits."

If you look at it under a microscope, you can see a kind of bag that sits tightly on the hair. From the side, only a small dash of white can be seen.

The further course of the life cycle

The next stage of the development cycle is called the larva of the first age. Outwardly, it is already not much different from mature individuals, the main difference is in size.

The further life cycle of small lice is as follows:

1. As soon as the parasite reaches the skin and eats for the first time, the process of larval molting will begin.
2. As a result of the first saturation, the louse will enter the nymph stage.

These steps are repeated two more times. Thus, lice survive three larval molts and three stages of the nymph.

At the end of the third molt, the insect becomes a full-fledged adult, capable of laying eggs.

Development Process Details

Nits are unable to leave their eggs immediately. With the help of jaws she makes punctures in the lid, but she will not be able to get out in this way. In order to leave the shell, the nits begin to breathe actively. The resulting air exits through the anus of the insect, accumulating at the bottom of the egg. When enough is gathered, he simply pushes the nits out.

How quickly head lice can multiply on a person’s head:

• Nits form in 5-8 days.
• After hatching, the larva becomes a nymph in 2-3 days, and sometimes even in a day.
• Before moving to a nymph of the second age, 5 days pass.
• A third-age nymph appears after another 8 days.

After this, the louse becomes a full-fledged adult. As a rule, she dies after about a month, but the longest recorded life span of ripened lice is 46 days. Mating with males occurs already in the very first hours from the moment of transition from the nymph stage to the adult.

Propagation Features

Females do not need several mating in order to fertilize all available eggs. This happens at a time, but the eggs are laid gradually. Each day, the female will produce a small amount of offspring, which varies depending on the type of insect.

The number of eggs per day in lice:

Thus, for the entire time of its existence, the pubic louse lays approximately 50 eggs, the head louse - up to 140, although most often the figure does not exceed 80. Most of the offspring produce a woven species, which manages to create about 300 eggs in life.

The shell, due to which the nits are attached to the hair, is formed during the gestation process, inside the female. In her gonads there is a sticky secret, which accumulates on future eggs.

Some of this secret leaves the body before the offspring are postponed, but most remain on the nits. The substance gradually hardens, reliably attaching the future louse to the hair.

What conditions are required for reproduction?

Lice and their reproduction are largely dependent on environmental conditions. The development of nits requires a certain temperature:

• The optimal indicator is 30 degrees.
• If the temperature drops below 20-22 degrees, then the nits will stop developing.
• The same thing happens if the thermometer shows more than 45 degrees.

If a temperature of 30-31 degrees is maintained around, then the reproduction of lice will take place easily and quickly. However, several more factors influence this. For example, it is easier for adults to mate, if you do not need to spend time searching for each other. Thus, the more lice on the head, the faster they multiply.

If several people infected with lice live in one room, then individuals will have an even greater choice of partners. It is for this reason that insect parasites caused so many troubles in barracks during the war.

Most often, lice are poisoned with shampoos containing insecticides. However, the most effective method of control is still shaving with subsequent water procedures. If the parasite cannot lay off its larvae on the hair, over time it simply rinses off. Preventive measures to avoid pediculosis do not exist.