Laboratory work in biology “External structure of insects”

If you look closely, the mosquitoes that are so annoying to everyone turn out to be very interesting insects. Although nothing special, the bloodsucker actually has a rather complex structure of the body and internal organs. There are many species of these dipterous insects, some of which do not pose a danger to humans: large centipedes, bell mosquitoes. Some insects are carriers of dangerous diseases. But all species have a similar body structure. Even scientists still don’t know everything about mosquitoes.

Description

The common mosquito (in Latin Culex pipiens) is a type of blood-sucking mosquito distributed throughout the globe. Insects are carriers of various diseases of humans (for example, meningitis, Japanese encephalitis, helminthic infestations) and animals (for example, avian malaria).

Mosquitoes are small insects whose size rarely exceeds 7 mm. Female mosquitoes are larger than males, but even their weight rarely reaches 1 g, unless you weigh an individual that has just sucked enough blood.

Appearance

Another name for the insect is the squeak mosquito. The mosquito squeak that irritates people is the sound made by the wings of an insect, which it flaps 500 - 700 times per second. But at the same time, the mosquito’s flight speed is low, the maximum value is about 3.2 km/h. Insects rarely move long distances, preferring to live and hunt in a very limited area.

Attention! The role of mosquitoes in nature is difficult to overestimate. Each generation takes many chemical elements from reservoirs, which subsequently enter the soil with the body of the dead insect, nourishing it. In addition, mosquitoes are an integral part of a large number of food chains.

How much blood can a female drink?

A sexually mature female squeaker mosquito feeds on blood. This liquid is rich in proteins necessary for the formation of eggs and their proper development. How much food can a bloodthirsty lady consume? A hungry mosquito weighs about 1-2 mg, and a lunched individual weighs about 3-5 mg. The special structure of the abdomen helps to accommodate this amount of blood. It is divided into 10 segments, connected by elastic membranes. When absorbing food and bearing future offspring, the pleura is greatly stretched.

Appearance and body structure

Almost everyone knows what an ordinary mosquito looks like. This is an insect with a thin elongated body, long legs, narrow wings, a small head, on which the proboscis is clearly visible. The color of insects is gray-brown.

Looking at a mosquito under a microscope, you can see that the wider thoracic part of the body consists of 3 segments. Each of them has a pair of legs with claws. There is a pair of scaly, almost transparent wings. When an insect flies, its rapidly moving wings create an unpleasant sound that we identify as the squeak of a mosquito. Female mosquitoes flap their wings at different frequencies, so they squeak in different tones to communicate with each other, communicate danger, or attract males.

The mouthparts of a mosquito of the piercing-sucking type are a proboscis, sharp stylets and file-like bristles. Studying a mosquito in an enlarged form, you can find that inside the proboscis there are 2 hollow channels, through one of them the insect injects a special secretion into the wound, and through the second it sucks out blood. The insect has a pair of compound eyes, the complex structure of which provides almost all-round visibility.

The common mosquito has a rather large brain by insect standards, consisting of 2 nerve trunks and large nerve ganglia associated with them. The heart of a mosquito is a muscular tube located in the abdomen that pumps blood.

Lifestyle

A mosquito is an insect that necessarily goes through an aquatic period of life in its development. Mosquitoes have four stages of development:

  1. Egg.
  2. Larva.
  3. Doll.
  4. Imago.

In all species, the first three stages occur either in water or in waterlogged soil on the banks of water bodies.


Life cycle of a mosquito

Structure of the larva

The larvae of different species emerging from eggs differ from each other in head shape. Those that feed from the surface of reservoirs have elongated and narrow heads. When feeding on plankton or bottom sediments, the larval head will be more developed in width than in length. Carnivores have a special head structure, different from the previous two.

The larvae have eyes on the sides of their heads. The mouth, depending on the type of nutrition, can be scraping or suction type. In predatory species, the mouthparts are adapted for catching and chewing prey. The chest plates are fused together. The abdomen consists of 9 segments.

The digestive tract of the larvae is almost a straight tube. Digestion of food occurs in the middle intestine. The digestive tract is supplemented by a pair of salivary glands and intestinal appendages.

Doll

The developed larva moves to the next stage: pupation. The pupa is lighter than water due to the large number of air chambers. At this time, almost fully formed small mosquitoes are at greatest risk, as they represent helpless food for fish.

The adult insect that hatches from the pupa dries up and sets off to look for a mate for reproduction.

How is a female mosquito different from a male?

The appearance and structure of a mosquito depend on its gender. The differences may not be easy to notice with the naked eye, but they exist and there are many of them:

  • the female is usually larger than the male;
  • females have small, simple antennae, males have lush and thick ones;
  • males feed only on plant foods, females need fresh blood at a certain period of life, so they bite people and animals;
  • in males, unlike females, the oral apparatus is underdeveloped and, as unnecessary, is not adapted to piercing the skin and sucking blood;
  • Females have better developed sensory abilities, as they need to search for prey from time to time.

Male and female

And finally, the female mosquito lives much longer than the male. But the truth is that because females attack people, they are in greater danger and die more often.

Reproduction

Mosquitoes feed on flower nectar. Even the females. But females need blood for successful and abundant oviposition. This is what causes their “bloodthirstiness”.

The female common mosquito (squeaker) attracts the male with a characteristic sound. That's why she still has her halteres. It does not buzz, but squeaks solely because of its size. Wings that are too small cannot produce a bass hum. If you hear a squeak in a swarm of mosquitoes, you can be sure that there are also females thirsty for blood there.

Even scientists have not yet been able to tell everything about mosquitoes when writing dissertations. However, many interesting facts about mosquitoes have been collected and you can get a general idea of ​​how the bloodsucker that prevents you from sleeping works, and why it prevents you from sleeping with its squeaking.

Habitat

Common mosquitoes live almost everywhere; the species is considered the most common. These insects can be found on all continents, even in the Arctic and Antarctica. True, in harsh conditions they are active for only a few weeks a year, but during this time they manage to bear numerous offspring.

The lifestyle of mosquitoes is inextricably linked with humans, whose blood is necessary for females to reproduce. Therefore, wherever people live, there are these blood-sucking insects. The habitats of insects even depend on their gender. So a male can spend his entire life in a forest clearing. The female is forced to move in search of warm-blooded prey. Most mosquitoes are found in places with high humidity.

Discovery history [edit | edit code]

People have always known about mosquitoes, but this species was first scientifically described by Carl Linnaeus in 1758. Later in 1775, Forscal described the same species in Egypt under the name Culex molestus

.
They both bear close physical resemblance to each other, and scientists later agreed to distinguish these mosquitoes by their willingness to bite people. Culex molestus
was more abundant in Alexandria, Rashid and Cairo.
Ficalbi (eng. Ficalbi) in 1890 proposed to call the squeaking mosquitoes that bite people “haematophagus”, and those that do not bite people, but feed only on nectar, to be called “phytophages”. Thus, in relation to Culex molestus,
partial attention was paid to the degree of biting of people; later their behavior was designated by the term “anthropophiles” [4] [5].

The mosquito belongs to the order Diptera, but it has a second pair of wings, which is reduced. Both pairs of wings flap simultaneously in flight at a speed of about 1000 beats per second, which creates a characteristic “mosquito squeak”.

Where do mosquitoes live and winter?

In nature, mosquitoes settle near bodies of water with stagnant water, in wetlands, this is due to the fact that insect eggs and larvae develop in the water. Females can also lay eggs in moist soil. Mosquitoes are often found in the forest, especially in damp, shady places. Mosquitoes living in cities choose basements (especially those that are periodically flooded and high humidity), warehouses, and apartments as habitats.

As winter approaches, insect activity decreases, all processes in the body slow down and, having found shelter, the mosquito goes into hibernation. As a refuge, bloodsuckers choose animal burrows, natural shelters, for example, cracks in stumps or fallen trees, fallen leaves, or the space under the bark of a tree. Insects often overwinter in the basements of country houses, barns, and livestock buildings. In the city, a mosquito can overwinter in any room, be it a residential apartment or the back room of a store.

Ecology [edit | edit code]

Squeak mosquito larvae develop on the shallows of rivers and streams in forests, forest-steppes and steppe zones.

Often the habitat of the common mosquito is urban areas. With the onset of cold weather, mosquitoes often fly into the basements of residential buildings, where, at room temperature and the presence of standing water, favorable conditions are created for their reproduction and the subsequent development of larvae and pupae. Mature mosquitoes from basements penetrate into apartments of residential buildings, and this can often happen in winter [15].

Food [edit | edit code ]

Eating sugars is the main characteristic feature in the life of a mosquito. Both sexes of different ages often feed on sugars, usually plant, but less often exofloral nectar and honeydew. Energetically, blood and nectar are interchangeable; females of some species have an innate dependence on one and on the other: she needs blood for the development of eggs, and sugar to maintain survival and maintain her life, for flight and to improve reproductive capacity [4] . Female squeak mosquitoes, like other representatives of blood-sucking mosquitoes, are characterized by a dual mode of nutrition, combining sugar and blood. Males feed only on plant juices and nectar [4] [11].

Nutrition of plant sugars [edit | edit code]

They feed on nectar on plants such as burdock ( Arctium

), yarrow (
Achillea
) and tansy (
Tanacetum
);
The observation was carried out in the vicinity of Moscow. The mosquito feeds most readily on tansy (7-10 females per flower) [16]. Among the mosquitoes that fed, the majority were virgin females, but pregnant females are rarely seen. A similar study was conducted in central and southwestern Sweden [17]. Of the 18 mosquito species collected on tansy flowers, Colex pipiens
(ssp.
pipiens
) and
Culex torrentium
accounted for 86%, with 52% being pregnant females. Fructose had a good effect on the body of collected mosquitoes in 81% [4].

In the Jordan Valley (in the Middle East), the squeak mosquito Culex pipiens pipiens

forma
molestus
was caught in the fields and reared in laboratory conditions [18].
This form feeds on sugars from six plant species, of which ' Ochradenus baccatus'
from the mignonette family gave its preference [4].

Blood feeding [edit | edit code]

According to some old works (Mattingly et all, 195; Shute, 1951, etc.) the non-autogenous form is pipiens

, was considered as omitophilic and, conversely, the autogenous form -
molestus
, belonged to anthropophiles.
Indeed, the anthropophilia of animal hosts is confirmed by a huge number of bites in urban and rural areas. However, the anthropophilia of this mosquito form should not be overestimated; molestus
caught in laboratory research were immediately bitten not only by humans, but also by birds, mice and guinea pigs [4] .

What do mosquitoes eat?

The mosquito's main diet is plant food, namely sugar-rich nectar and plant juices, which provide the carbohydrates necessary for life. Squeaking mosquitoes are not very selective in food, but there are still plants that they prefer. These include tansy, burdock, and yarrow.

To procreate, the female needs protein and other useful substances, which she receives from the blood of warm-blooded animals, including humans. The oral apparatus of the female mosquito is well developed and adapted for this type of feeding.

Insects are able to sense their prey at quite a distance. The smell of sweat, carbon dioxide released during respiration and heat are what mosquitoes fly to.

On a note! The widespread belief that insects fly towards the light, according to scientists, is erroneous. Mosquitoes are not attracted to light, but to the heat emanating from its source.

Autumn equinox: traditions, signs, fortune telling

Folk signs

  • You cannot take on a new business a week before the equinox, or 7 days after.
  • What is the weather like at the equinox - like this all autumn!
  • If you want to avoid illnesses in the remaining days before the Young Sun, do not overexert your body. You cannot increase physical activity. Keep track 7 days before the event and the following week.
  • If you want, get up early on the equinox before sunrise and wash or take a shower.
  • If birds are actively flying south this day, expect a harsh winter.
  • If by the equinox the rowan and birch trees are dressed in yellow, the winter will be cold.
  • If you want to live richly and happily, celebrate the equinox for a week.
  • Rowan is rich in harvest - autumn with rain, and winter with frost.
  • If there are few berries on the rowan tree, then wait for a dry autumn and the first frosts without rain.
  • Lots of acorns means little snow at Christmas.
  • If you dream of a strong family, have a wedding on the equinox.
  • If you met a wedding procession this year, then your family will be happy all year.

How does a mosquito bite?

Having discovered the victim, the female mosquito lands on the skin, hooking its claws, then bites, that is, pierces the skin with sharp stilettos. Then the insect injects saliva into the wound, which has an analgesic effect and slows down blood clotting. After this, the bloodsucker plunges its proboscis into the nearest blood vessel and begins to suck blood from it.

Mosquito bite

Examining the process of a mosquito bite under a microscope, you can see that the strong proboscis is at the same time very flexible. In search of a suitable capillary and at the moment of penetration into it, the proboscis can bend freely and turn in different directions. Most often, the bite lasts 1-2 minutes, but sometimes, in order to get enough, the female sucks blood for 3-4 or even 5 minutes.

Fly under a microscope

The fly is one of the most common insects. She lives wherever there are people and there are favorable living conditions.

Under a microscope, it is clearly visible that the entire body of the fly is covered with hair. Hairs, as well as large wings, protect it from getting wet. This is the hairy belly of a fly. On the fly's head there are antennae - this is the organ of smell. Most of the head is occupied by the eyes. They consist of 4 thousand facets and see 360 ​​degrees around them. Plus, the fly has lightning-fast reactions, making it difficult to catch.

The housefly's proboscis is soft and can only absorb liquid food. If the fly likes a hard piece, then it actively begins to inject digestive enzymes into it so that it breaks down. She tastes the food with her paws. They contain taste receptors. She rubs her paws against each other all the time, clearing away any stuck-on debris.

But the autumn fly - a blood-sucking fly - has a sting with which it bites painfully. In autumn, this type of fly becomes especially angry, as they try to stock up on protein for breeding.

How many times can the same mosquito bite?

Very often, when an annoying insect circles somewhere nearby, every now and then perching on various parts of the body, an irritated person has a question about how many times a mosquito bites.

Unfortunately, the answer is disappointing - there are no restrictions. The female tries to get the amount of blood she needs at one time. But if something bothers her, she will fly away and then return again and again until she is satisfied. In addition, do not forget that it is almost impossible to distinguish one mosquito from another. Therefore, it may seem to a person that he is being chased by one mosquito, although in fact several individuals fly up to him one by one.

Are mosquitoes beneficial?

Much is known about the harm mosquitoes cause, but the benefits of these insects are also considerable. For example, being carriers of dangerous infections, insects regulate the numbers of some animals.

Before you dream of a world without mosquitoes, it’s worth finding out what benefits they bring:

  • feeding on the sap and pollen of plants, they participate in pollination;
  • Fish, insects, spiders, frogs, birds feed on mosquito larvae and adults (for some animals, mosquitoes are the main food);
  • developing in water, the larvae receive many microelements with which the adult insect enriches the soil when it dies;
  • during the development process, mosquito larvae filter and purify water in reservoirs, feeding on organic substances, various microorganisms, and rotten plants;
  • are an important link in various food chains (one of the most famous is the “mosquito-frog-heron”).

The enemy of mosquitoes

Scientists have found that insects often choose the most painful places on the human body to bite, since more heat emanates from them. The benefit of mosquitoes is that when they bite, they inject saliva, which thins the blood. Thanks to this, blood supply to the affected area improves and even small blood clots in the capillaries disappear.

The main functions of mosquitoes in the natural environment

By studying reference books, you can learn about several important tasks that are assigned to the presented species of insects:

  • Bloodsucking pupae that float to the surface of the water are food for fish and cold-blooded animals;
  • Mosquito larvae consume tiny microorganisms, an excess of which can lead to changes in the bacteriological composition of the reservoir;
  • The imago (adult) acts as a delicacy for swallows, sparrows, and other small birds;
  • During the period of their life, insects consume a number of microelements, and when they die, they transfer iodine, iron, cobalt into the soil, thereby increasing its level of fertility.
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