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Text 17

Internal anatomy

Digestive system

The pieces of leaves bitten off by the beetle pass through the pharynx into the oesophagus, where they come in contact with saliva. From the oesophagus, they pass, in small portions, into the muscular, or masticatory, gizzard, which is lined with toothed chitinous plates. The plates grind the pieces of food in a process that resembles chewing.

Then comes the mesenteron which has glandular walls that secrete digestive juices. Under the influence of these juices the food is digested, or dissolved. The mesenteron is the beetle's digestive region. The digested food is absorbed by the walls.

The waste products enter the rectum, accumulate, and are periodically excreted through the anus.

Respiratory System

The beetle's respiratory system is very interesting. The oxygen is taken direct to the various parts of the body through narrow openings (spiracles), each of which communicates with a thin tube, a trachea. The tracheae form a ramified network, branching out into all parts of the body - to the eyes, feelers, legs, etc. This system provides for the free access of air to all the tissues.

At the end of some of the tracheae are air-sacs. The air-sacs enlarge reducing the beetle's body-weight and making flight easier (1).

Circulatory System

Oxygen is distributed to the tissues through the tracheae. Carbon dioxide is taken out in the same way. The blood does not carry the gases. The blood washes the tissues in nutritive substances which it receives from the intestine.

The circulatory system consists of the heart and the aorta. Circulation is achieved by the contractions of the tubular heart, which lies in the dorsal side of the body and is divided into a number of separate chambers. Each has two openings one on either side (2). The anterior end of the heart opens into the aorta; the opposite end is closed. When the heart expands, blood flows in from the body cavity through the openings in the chamber walls. When it contracts the openings are closed and the blood is directed into the aorta, whence it proceeds to fill the space between the various organs. The beetle has аn open circulatory system.

Excretory system

The excretion of fluids harmful to the organism takes place through thin excretory tubules. One end of each opens directly into the intestine .between the mesenteron and the rectum. The opposite end is blind, and lies in the body cavity.

The blood carries waste products from the tissues to the body cavity, where they penetrate into the tubules through their walls, pass into the intestine, and are excreted.

Insects. Characters

The May-beetle is a typical representative of the Arthropoda. Its body is covered with chitin, its legs have joints.

The May-beetle is an insect. Insects, one of the groups of the Arthropoda, have the following features in common: a head, a thorax, and an abdomen; three pairs of legs; a pair of well-developed antennae; compound eyes (most of them); respiratory organs made up of tracheae; wings (the overwhelming majority).

Insects form the most numerous group among the Arthropoda.

Reproductive System

The sexes are separate. The female has ovaries. Each ovary has many thin-walled tubes full of semi-transparent eggs. The male organs are the testes – two long, white, coiled tubules - which carry sperms.

Egg-laying

Soon after mating, the male beetle dies. The females find sоmе young pines growing on sand and deposit their eggs in the soil in several pods. The eggs are not bigger than hemp seeds.

Development

The eggs hatch out into white larvae which look somewhat like worms but have a chitinous cuticle, segmented legs, strong thick-set jaws, and clearly visible spiracles. The wings and eyes, sо well developed in the adult beetle, are absent. The larvae feed on the roots of young pine-trees, suger-beet, and other crops causing great damage.

As the larvae grow they shed their skins or moult. A new skin is secreted just before (1) the.moulting process begins. Before it hardens, the new skin is soft and thin, and can stretch, allowing the young grub to grow.

After five moulting the larva becomes a pupa, which resembles an adult beetle and has noticeable rudimentary wings, antennae, and other organs. The pupa undergoes a period of complete rest when it lies quite inactive in the earth (does not take food and does not grow). In fact, great biological changes are going on in preparation for the transformation into an adult beetle. Throughout the pupation period the young insect lives on the nutritive substances stored up during the larval stage.

Some time later the pupa develops into an adult beetle.

Tasks

  1. Write down whether the following statements are true or false. Give extensive answers.

  1. Mesenteron has glandular walls that secrete digestive juice.

  2. The oxygen is taken direct to various parts of the body through spiracles.

  3. Circulation is achieved by the contractions of the tubular heart and the aorta.

  4. The ends of thin excretory tubules open directly into the intestine.

  5. The bodies of all insects are covered with chitin.

  1. Complete the sentences using the text and translate them into Russian.

  1. From the oesophagus they pass, in small portions, into … .

  2. … are periodically excreted through the anus.

  3. … into all parts of the body – to the eyes, feelers, legs etc.

  4. When the heart expands, blood … .

  5. When it contracts the openings … .

  6. … pass into the intestine and are excreted.

  1. Answer the following questions on the text in written form.

  1. How and where does digestion take place?

  2. What role do air-sacs play?

  3. How does circulation in the body of the beetle occur?

  4. What function does blood play?

  5. How are waste products excreted?

  6. What common features do insects have?

  7. How does the development of the larvae occur?

  1. Translate a passage into Russian in written form.

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