Answers to test control questions …………………………………………… .51.

Literature ………………………………………………………………………………………… .52.

INTRODUCTION

Throughout their history, in one way or another encountering insects, people already have enormous knowledge about these amazing creatures. Entomologists, chemists, biophysicists, design engineers, genetics, architects, physicians of various fields study insects.

Unfortunately, within the framework of the course of general biology at a medical university, students are limited to studying the section “Basics of Medical Entomology”, which includes a rather superficial overview of the representatives of units of epidemiological significance.

The purpose of our manual is to somewhat expand and deepen the information on this section in addition to the material of the textbook, which will allow students to save their scarce time by searching for material in various sources.

The manual "The medical value of insects" is presented in three sections.

The first gives a general description and classification of insects, morphology, biology, the epidemiological significance of the most important representatives of orders with complete and incomplete metamorphosis. Descriptions of some vector-borne diseases are given.

The second section is devoted to poisonous insects, since this important material in the textbooks is presented very briefly. Their toxicological classification is given and descriptions of insects with a stinging apparatus, with poisonous blood and tissues, with a poisonous oral apparatus, a picture of poisoning and first aid are given.

For better perception, the theoretical material is provided with illustrations.

The third section is presented by the questions of test control on the material studied and the answers to them.

At the end of the manual is a list of references.

Section I. Morphological and biological characteristics. The epidemiological significance of insects

1. General characteristics of Insects.

Insects are the most numerous class of arthropods. It includes more than 2 million species. For insects characterized by a clear separation of the body head, chest, abdomen.

Head   consists of four fused segments bearing respectively four pairs of appendages, which are modified forelimbs.

The first pair - antennae, or tails, - organs of smell and touch. The second - the upper jaws - the mandibles, the third and fourth pairs - the lower jaws - the maxillae. The insects' mouth apparatus is formed by the upper lip (skin fold of the integument of the head), a pair of upper jaws, a pair of lower jaws and a lower lip, which is formed by merging the second pair of lower jaws. According to the variety of feeding methods, the mouthpieces of different groups of insects differ significantly in structure. They may be of the gnawing, gnawing-sucking, licking, piercing-sucking, sucking type. However, all this diversity is the result of a change in one source type - the gnawing mouth apparatus.

Abdomen   consists of 4-11 segments. The extremities on the abdomen are absent. Only in some species, modified limb residues are sometimes preserved, for example, in the form of an egg deposit or forks at the end of the abdomen, which help to make jumps.

Insect covers   formed by a single-layer epithelium, the hypoderm, and the chitinized cuticle secreted by it, which plays the role of the external skeleton and protects it from the effects of various factors, including mechanical damage. In addition, chitinous cover prevents evaporation of moisture from the body of insects. During the period of growth, insects molt several times - they drop chitinous cover, under which a new one develops. The skin is rich in various glands (fragrant, waxy), outgrowths in the form of spines, setae or hairs.

Muscular system   represented by beams, which are attached from the inside to the outer skeleton of insects.

Digestive system begins with the oral cavity, where ducts of the salivary and spinning glands open, like those of a butterfly caterpillar. The anterior intestine is differentiated into the pharynx and esophagus, which often has an extension - goiter. Some insects have a chewing stomach. In the midgut are numerous folds, which, apparently, are homologous to the liver of other arthropods. The posterior intestine, in addition to the removal of digestive residues, is involved in the secretion of metabolic products.

Excretory system represented by malpighian vessels (of which there may be 100 or more) - long thin tubules, which, with their blind-closed end, lie in the body cavity, and the other end up in the intestine, on the border of the middle and back parts. Metabolic products also accumulate in the fat body, which serves as a kidney of accumulation.

Respiratory system   insects are represented by the tracheal tube system. They permeate the entire body and deliver oxygen directly to the cells. Trachea occurs in the embryo as a protrusion of the ectoderm, have a chitinous lining that prevents the walls from falling. On the sides of the body, there are up to 10 pairs of spiracles (stigmas) leading into the channels from which the trachea originates.

In connection with the development of trachea open circulatory system simplified, the hemolymph takes almost no part in the exchange of gases, but carries nutrients and hormones to the tissues of the body. The blood circulates in the heart, then moves through the aorta, and from it enters the body cavity, washing all the organs.

Nervous system   insects are represented by the brain, the subpharyngeal ganglion, and the segmental ganglia of the ventral nerve cord. The brain consists of the anterior, middle and posterior parts. In the forebrain are mushroom bodies, which are especially developed in insects with complex social behavior (bees, ants). The nerves are moving away from the brain to the antennas, eyes, upper lip and the popharyngeal node.

Insect development   complicated. They are dioecious animals with pronounced sexual dimorphism. Postembryonic development is carried out with complete and incomplete transformation.

In the first case (butterflies, beetles, bees, flies, etc.), the larva, which differs significantly in structure and way of life from an adult individual, leaves the egg. It intensively feeds and grows and after several molts turns into a motionless pupa. Under the cover of the pupa, reorganization of the organs and tissues of the larva occurs, ending with the release of an adult insect, the imago.

In case of incomplete transformation (locusts, grasshoppers, cockroaches), the larva is structurally similar in general to an adult insect, but differs from it in its small size, underdevelopment of its wings and the reproductive system. The larva grows, periodically sheds and turns into an adult insect.

The insect class includes more than 20 orders, the most important of which are as follows:

Insect class (Insects)

Nadotryad 1. Insects with incomplete metamorphosis (Hemimetabola)

Orthoptera

Cockroach squad (Blattoidea)

Lice squad (Anoplura)

Hemiptera detachment, or bugs (Heteroptera)

Nadotory 2. Insects with complete metamorphosis (Holometabola)

Cockroach, or beetles (Coleoptera)

Lepidoptera, or butterfly (Lepidoptera)

Hymenoptera order

Flea Squad (Aphaniptera)

Diptera squad (Diptera)

We will focus on the representatives of units of medical value.

Goals:

Educational:   expand and deepen knowledge of arthropods by studying the structure of insects; consider the characteristic features of the external structure of the insect on the example of the May beetle; to study the characteristics of the internal structure of insects; get acquainted with the value of insects in nature and human life;

Developing:   develop the ability to compare, draw conclusions; create conditions conducive to the development of students' cognitive interest in the study of various biological objects;

Educational:   to form students autonomy, ecological culture.

During the classes:

1.To enhance the cognitive activity of students we make a riddle:

Growing up a worm, eating a leaf,

Then I fall asleep, I wrap myself

I do not eat, do not look, lying motionless.

But with the new spring, I suddenly come to life,

I leave my house like a bird, I flit.

Who are we talking about in the riddle? (About the butterfly).Why is the butterfly first a worm? What does a butterfly eat? What does a butterfly caterpillar build its house from?

We will be able to answer these and many other questions by examining insects.

2. The stage of studying a new material includes viewing a video lesson followed by a discussion.

Download video "General characteristics of Insects"   from Yandex disk

Insects - the only class among invertebrates, whose representatives have wings and are able to fly.

Despite the huge diversity of insects, they all share common features. Their body is clearly divided into three sections: the head, chest and abdomen. They are interconnected movably.

On the head there is one pair of antennae, eyes allowing orientation in space, and an oral apparatus necessary for capturing food.

They have two large complex eyes, between which there may be several small simple eyes.

Antennae are very diverse in length, number and shape of segments. They can be filiform, comb-like, pinnate, club-shaped and plate-like.

Insects feed on a variety of foods, and depending on the nature of the food, they are found different types   mouthpieces. Species that feed on solid plant and animal food have a gnawing mouth apparatus (beetles, dragonflies). Species that feed on liquid food (plant sap, animal blood, flower nectar, decomposed tissue and plant tissue) have sucking (butterflies), piercing-sucking (lice, mosquitoes), lacquering (bees), or licking mouth-apparatus (flies).

The chest consists of three segments, which are called the prothorax, the mesothorax and the posterior loch. Each segment carries one pair of walking limbs. Insects have three pairs of legs. The limbs, as in all arthropods, consist of segments that are movably interconnected by joints. This allows the animal to make a variety of movements. Walking legs can be jumping, they are strongly elongated (in a grasshopper), digging - they shorten and become massive (in a bear), swimming (in a swimmer), collective (in a bee) and running (in a ground beetle).

The belly of insects may contain a different number of segments, and moreover in primitive species of segments. For example, a dvukhvostok abdomen consists of 11 segments, while the more highly developed ones have only four to five segments. The extremities on the abdomen are absent. Primitive species contain underdeveloped limbs on the abdomen, i.e., their rudiments. At the posterior end of the abdomen, there may be appendages in the form of ovipositor (in grasshoppers) or sting (in bees, wasps).

The body of insects is protected by a cuticle, which is covered with a waterproof film on the outside. It protects the insect from water loss. In the covers there are numerous hairs and numerous glands.

Muscles that are very well developed in insects are attached to the integument of the body from the inside. This allows insects to make very complex movements. The total number of muscle bundles can reach two thousand, while in humans there are only about 600 skeletal muscles. Adult insects do not grow and shed.

Get to know internal structure   insects. Most of the internal organs are concentrated in the abdomen.

The digestive system is well developed. On the head is a mouth surrounded by parts of the oral apparatus. In the oral cavity open ducts of the salivary glands. The short sip continues into the longer and narrower esophagus, which in many species forms an extension — the goiter. In it, food is delayed and exposed to digestive enzymes. There is a stomach behind the goiter, followed by the middle gut. The midgut extends into the back, which ends with the anus. The liver is absent. Food from insects can be very diverse. There are herbivorous insects (eg, living in the ground beetle larvae, wireworms - wireworms feed on plant roots; weevils damage the flowers of apple trees, butterflies, caterpillars feed on the leaves), predatory insects - ladybugs eat aphids and smaller insects, ground beetles feed on caterpillars and even earthworms . The grave-digging beetle, gray meatfly, feed on animal corpses. Among insects there are omnivores that feed on various plant and animal products, such as cockroaches.

The respiratory system is represented by trachea. You already know that tracheas are numerous branching tubes that penetrate the whole body of an insect and deliver oxygen to all organs and tissues. The trachea begin with holes, or spiracles, located on the sides of the two posterior segments of the chest and segments of the abdomen. There are up to 10 pairs of such holes.

The circulatory system, like all arthropods, is open. The heart is located on the dorsal side and looks like a long tube. The only vessel leaving the heart goes from the heart to the head end of the body. Since insects have a very well developed respiratory tracheal system, the circulatory system does not participate in the transport of oxygen and carbon dioxide, but serves only to transport nutrients to organs and tissues and to remove metabolic products from them. Hemolymph is usually colorless.

The excretory system is represented by malpighian vessels located on the border of the middle and posterior intestine. Each malpighian vessel has the form of a thin tube, the free end of which ends blindly, and the other flows into the intestinal cavity. The number of vessels in different species varies from 2 to 200.

The nervous system is represented by a complex supra-pharyngeal ganglion - the brain, the subpharyngeal ganglion and the ventral nerve chain, which is characterized by the fusion of ganglia. The brain consists of three parts: anterior, middle and rear.

The reproductive system. All insects are segregated. In many species, sexual dimorphism is pronounced in terms of color, size of body, shape and size of antennae, presence or absence of wings. Reproduction is only sexual. They have paired genital glands. The males in the abdomen are the testes, from which the vas deferens, flowing into the ejaculatory canal. Females have ovaries that open into the oviducts, connecting to an unpaired vagina. Fertilization is internal. In some species, live birth occurs.

Now consider the importance of insects in nature and their practical significance. Insects have a huge positive value:

· They are the most important link in the circulation of substances

· Butterflies, bees, wasps, bumblebees - pollinators of flowering plants

· Soil larvae, ants are involved in soil formation

· Bees - a source of food and medicinal substances (honey, wax, propolis)

· The larvae of silkworm butterflies are a source of natural silk

No less important are the negative consequences of insect activity:

· May beetle, locust, aphid, Colorado potato beetle - pests of plants, destroy crops of agricultural plants

· Flies, cockroaches, fleas, lice - carriers of human diseases

· Insect bites (bees, wasps) are painful and can be poisonous to humans.

3. Consolidation of the material studied (conversation on the topic) and summarizing the lesson.

To summarize, we recall the characteristic features of the Insect class.

Insects have:

· Three parts of the body (head, chest and abdomen);

· One pair of antennae;

· Three pairs of walking legs;

· Wings;

· Respiratory organs are trachea;

· Organs of excretion - malpighiev vessels.

Insects are representatives of the type of arthropods. Their characteristic feature is the presence of limbs, consisting of individual segments. Insect class is the most numerous and has about 1 million species. Cockroaches, grasshoppers, beetles, butterflies, wasps, bees - it is simply impossible to list them all! What features allowed them to get so widespread? The theme "Insects and their features" is very interesting. Let's take a closer look at it.

Structure

The parts of the body that insects have (see photo in the article) are the head, chest, and abdomen. On the head is a pair of antennae, the length of which varies and serves as an important systematic feature.

Miraculous transformation

The development of insects occurs in a special way. Organisms with larvae form imago - an adult. Moreover, these two stages in morphological features do not differ by anything other than size. This is how the development of such units as cockroaches, orthoptera, termites, lice, bugs and praying mantises occurs.

In coleopterans and fleas, a different type of transformation is complete. Its essence lies in the fact that the larva at an early stage of development emerges from the egg, turning into a pupa. At this stage, the destruction of the original organs and the formation of new ones. This is how an adult is formed. An important fact is that the larva and the imago are not similar in appearance. For example, at the initial stage of development is similar to a small worm.

Habitat

Characteristic signs of insects

Insects (photos demonstrate the diversity of representatives) have signs by which systematics distinguish them into a separate class of the type Arthropods. These are three pairs of limbs and parts of the body (head, chest, abdomen), the presence of a pair of antennae on the head, the respiratory organs - the trachea, and the discharge - malpighian vessels.

The variety and significance of insects

What insect of the order Hymenoptera is public? Of course it is a bee. Its main value is to obtain honey and pollen from the pollen.

The representatives of the squad cockroaches fly very badly, but they are well oriented in space with the help of long antennae.

Locusts, polaroks and crickets are orthoptera. This group includes grasshoppers and crickets, which have special devices. This is the so-called mirror - a thin membrane - and a bow - vein with teeth.

Insects belonging to the order Bugs have a flattened body on which wings do not form. Their absence is compensated by the ability to easily jump a decent distance.

Insects are all members of the order beetles that have hard elytra, tightly covering the abdomen.

Who among us has not admired the fluttering flight of beautiful butterflies? They are also insects. They are not only beautiful. Many of them are useful. So, "heads" the whole production. It is artificially bred in many countries of the world. And the product of its vital activity is natural silk.

Thus, insects are a class most of which are adapted to flight. Thanks to a fairly high level of organization, they have mastered all habitats, occupying their niche in the system of the organic world.