Lice are obligate external parasites of mammals. These insects have adapted to living in animal wool and feeding exclusively on their blood, they can not live outside the owner's coat and specialize only on one species or only a few closely related species of animals.
For example, a human louse can only live on a person and some monkeys. Elephant lice can only hit elephants, and hares - only hares. Lice of one species of mammals can not affect other species.
So, cat lice is not able to parasitize on a person, and a human louse does not live on domestic animals (many without knowing it, often seriously suspect if their children have caught a cat or dog). So far, scientists have not found lice in representatives of the marsupial squad.
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On birds, its own peculiar group of insects parasitizes, called fluffy. They are more diverse than the lice themselves, and it is believed that they cause in general less inconvenience to the owners than parasites of mammals. Lice that parasitize animals are called withers in science, and in addition to blood, some of their species can feed on skin cells and secretions of host glands.
The human louse for a short evolutionary period of human habitation on the planet managed to split into two forms, which theoretically are able to turn into different species. One of these forms lives on the head and is called the head louse, the other lives in clothes and is called a dress (or else - a linen louse).
They can produce viable offspring, but because they practically do not meet together in real conditions, they do not mate and are more and more divided.
In addition to these forms, the pubic louse parasitizes on the person, which differs significantly from the head and lice in size, lifestyle and appearance.
What do lice look like?
Lice are rather small insects. In the photo under the microscope they can see all the attributes inherent in their biological form - six legs, segments of the body, the cephalothorax and abdomen, the antennae:
Below are some more photos of human lice. It is characteristic that at all stages of development they do not have wings, like their relatives are withers:
Without a microscope, lice look like tiny light gray insects. The flesh lice are slightly lighter and appear almost white. Pubic lice are the darkest, and their body is shortened, due to which they resemble small crabs.
Among the hair of parasites is difficult to identify. To look at how lice look, you can, for example, on a light fabric, on the palm of your hand or on your finger.
In the photo - a louse on the finger:
And on the next photo you can see how the lice look in their hair - their normal habitat:
In size, the head louse reaches a maximum of 4 mm, usually - about 2-3 mm, the same is the same. The pubic louse is the smallest, has a body length of 1-2 mm. In the picture, lice pubes are well distinguished by rather massive sturdy paws and a rounded body:
On a note
It will be quite difficult for a non-specialist to distinguish lice without a microscope from withers. However, you can always be sure: if a parasite is caught on a person - it's a human or pubic louse.
What is the difference between different types of lice?
Different types of lice can be distinguished from each other even without a microscope.
If the insect is light, almost white, then it's a louse. The photo shows how the louse looks of this form on clothes:
If the insects are dark and their abdomen is greatly shortened (looks broad) - these are pubic lice. Photos of them on a white background and in the hair are presented below:
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Pubic and head lice were very common in antiquity among humans. The famous Roman emperor Sulla suffered from pubic lice. In describing the monstrous diseases with which he was sick from his depraved lifestyle, all his contemporaries invariably described thousands of parasites that literally poured from him, and the slaves who were left day and night from his body were filmed.
If the insect is dark and has a long abdomen, it belongs to the typical head lice. In the photo below, lice in the hair are clearly distinguishable:
Even easier to distinguish lice from the place on the body where they were found or caught. Lice in the hair on the head - only head, pubic, groin and anus areas, in the armpits and in exceptional cases - on the brows - pubic. Parasites on clothing and hair on the chest are usually clothes.
With other parasites, lice are difficult to confuse, because they look completely different. Bedbugs are much larger than lice and do not occur on the human body during the day, and fleas are almost black and jump well.
But the main difference between all these parasites, as well as mites against lice, is that they avoid the hairy parts of the body. Lice in the hair and prefer to parasitize - their paws are ideally suited for attaching to hair bundles.
On the photo - lice on the hair:
And in the next photo below you can see how the lice look on the folds of clothing:
Reproduction and life cycle of lice
Lice are insects with an incomplete cycle of transformation. This means that their larvae, emerging from eggs, are very similar to adult insects, differing only in size and inability to reproduce.
On the images of lice, we can distinguish larger imago - sexually mature parasites - and larvae:
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Insects with incomplete cycle of transformation include also cockroaches, crickets, grasshoppers, bugs. And insects with a complete transformation include, for example, butterflies, beetles, mosquitoes, flies, wormlike larvae which look quite different than adults.
Larvae of lice are called nymphs, and adult individuals are imago.
Louse eggs are called nits. They are immobile and transmitted from person to person, as it is thought by especially cautious citizens, in most cases can not.
A feature of nits is that at the exit from the oviduct of the female the egg is covered with a thick layer of sticky secretion and immediately comes into contact with the hair to which it adheres. The secret quickly hardens, and the nits are so firmly attached to the hair that it is very difficult to tear off it - it is easier to pull the hair itself.
Lice and nits co-exist side by side, but usually nits are more noticeable, as adult insects often sit on the skin at the base of the hair, and the nits are located directly on the hair.
In the photos below, you can see in more detail what nits and lice look like:
Lice reproduce very quickly. Each female lays daily about 10 eggs, of which a larva leaves in a few days.
Then the larva grows and moults three times, which takes about 14-16 days. After the last molt, the nymph becomes an adult louse and almost immediately mates with a representative of the opposite sex. The cycle time from egg to egg is about 18-22 days, in ideal conditions - 16 days.
With a decrease in temperature, lice and nits develop much more slowly, and the duration of the cycle of their reproduction can stretch for up to a month or more. The optimum temperature for the reproduction of lice is 32-33 ° C.
The photographs below show lice and nits on the hair:
On a note
With a sufficient length of hair on the head, even in winter, on the street, the temperature near the skin on the head does not practically drop below 25 ° C, and therefore lice on the person quietly reproduce all year round.
How to reproduce lice is well demonstrated in the video below. It is good to consider what adult lice, nits and larvae look like at different stages of development:
Nits of different types of lice differ slightly from each other. In pubic hair, they look a little smaller, the clothes are bigger and usually are in the seams of clothing. Nits of laundry lice can be completely destroyed, for example, by boiling clothes.
Below is a photo of pubic lice and nits on the hair:
And the next photo shows nits of a lice-like form:
Lifestyle and optimal conditions for the existence of lice
Knowing everything about lice, it is easy enough to develop and apply measures to destroy them.
Lice are constantly present on the body of a person or his clothes. It is enough to change clothes regularly and wash clothes at high temperatures, and even if they become infected, the louse will die. Lice and nits of a uniform can reproduce normally only if the person does not change clothes for months and does not wash. This is typical for vagabonds and homeless people.
Pubic and head lice are highly dependent on the length of the hair. On the hairless part of the body they can not live at all. The best way to get rid of them is to shave your hair where parasites were found. Even at the beginning of the last century, to fight lice in the first shave their heads, and therefore it was believed that a shaved man with a naked man suffered lice.
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In recent years, scientists have observed a sharp reduction in the infectiousness of pubic lice throughout the world. They associate this with the fashion on the shaving of the pubic both men and women. On a hairless pubic lice, lice can not live, and even after a sexual intercourse with an infected person they are not fixed on a new victim.
Sometimes lice can infect completely unexpected places. For example, underarms and eyelashes. Knowing how lice and nits look like, they can be easily identified here, but the removal of parasites from these places requires certain efforts:
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It is known that sometimes a pubic louse transmitted from the mother to a child can infect the baby's eyebrows. This should be taken into account in the prevention of pediculosis in a large family.
Below are some more photos with lice and nits on eyelashes:
Lice eat several times a day: at normal temperatures, even a three-day hunger strike is fatal for them. At low temperatures, they can fast for up to a week.
Louse lice constantly move from clothing to the body of a person. If the clothes are even removed for a week, most of the lice and their larvae die.
Lice die at temperatures below 0 ° C and above 45 ° C. With a gradual and not a severe drop in temperature, they can fall into a state of suspended animation and starve for several weeks.
The spread of lice between people
Lice are transmitted in most cases with direct physical contact of the infected person with the uninfected. Most often lice are infected today with preschool children, who play and fight together.
Sometimes lice are transmitted by common use of headgear and hair care products. But this transfer plays a much smaller role in the spread of lice.
In general, lice can be infected in any public places where close contact of clothes and people is possible. For example, in public transport or at various mass events.
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Lice can stay in the water for a long time, and therefore sometimes infection occurs in swimming pools and natural water bodies. But such cases are extremely rare and they are especially not to be feared.
In this case lice are afraid of sharp smells. To protect against them, it is enough to spray hair with eau de cologne or spirits with the smell of eucalyptus or mint before going out to the public, and insects are less likely to move to hair when contacting children and adults.
On a note
Do not assume that head lice can only occur in homeless and sloppy people. The danger of these insects lies in the fact that they are easily transmitted to children and adults, regardless of the level of culture, and they can be infected at home or even in an elite kindergarten. And before they multiply in quantities, which will cause unpleasant feelings, they can have time to spread throughout the collective or family.
But really a satellite of unsanitary conditions is a louse.
But if the infection has suddenly occurred, lice should be removed without delay. On the correct fight against these parasites, read in other articles on our website in the section "How to get rid of lice."
Getting rid of lice and nits at home for 1 procedure: