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

1. What animals or plants cause damage to forests?

2. What measures should be taken to protect forests and gardens?

3. How is chemical control carried out?

4. What is “stomach poisons”?

5. How does DDT work?

6. Why and when is the use of DDT and other toxic chemicals banned?

7. What do physical methods of control consist of?

8. What can you say about biological control?

9. How do you understand “cultural control”? What does this method consist of?

10. Can damage be avoided and how?

4. Translate a passage into Russian in written form. Text 19

Insects which transmit disease

Mosquitoes (Gnats)

Mosquitoes, or their more common variety - the Northern House Mosquitoes or Gnats, appear early in spring, as soon as the snow has melted away. They are all females that have survived the winter. They hurry to small stagnant, warm ponds to deposit eggs.

After several sunny spring days swarms of very active larvae appear.

They live in the water but breathe fresh air. The tip of the abdomen carries a breathing tube, the opening of which is at the surface when the resting larvae breathe. The body is kept at a certain angle to the water surface and the head hangs downwards. The larvae feed on decaying vegetable matter and floating microorganisms, which are caught in the mouth.

The comma-shaped pupa is quite large and very active, and spends its life in the water. It has a pair of breathing trumpets on its chest.

When after pupation the adult insects emerge, the transformation takes place at the surface of the water. The chirm pupal skin splits on the dorsal side, and a mosquito breaks out. Until it dries and flies away it uses the skin as a raft. This is a critical period in the mosquito's life-cycle: the slightest disturbance can lead to death. They do die in great numbers.

Among the blood-sucking mosquitoes it is only the females that bite. They need blood to ripen their eggs. They may be regarded as parasites but not "endoparasites" (internal) like, for instance, the worms, because they do not live inside the host; they are "ectoparasites" (external) because they take their food on the host's surface, spending only a short time there (while sucking blood). The males are vegetarian (sucking the sap of plants).

The Malaria Mosquito is easy to distinguish from common gnats: at rest its body is carried at an angle to the surface on which it stands, with the posterior end elevated. The ordinary, northern house mosquito holds its body parallel to the surface.

Both types lay eggs on the surface of shallow, still water. Only the Malaria Mosquito lays its eggs singly, sometimes in hollow trees holding stagnant water.

Malaria Mosquitoes are dangerous parasites which should be destroyed. Control is quite simple while the larvae are still in the water: oil or kerosene blocks breathing tubes, or trumpets, of the larvae or pupae, suffocating them.

House Fly

The House Fly is dangerous because it spreads various infectious diseases as well, as the eggs of parasitic worms. The fly larvae live and develop in dustbins or manure - this is where the eggs are usually laid.

Before it pupates, the larva crawls out of the manure or refuse and burrows into the earth. The pupa is protected by a small, brown puparium, which looks like a tiny barrel and consists of the last larval skin which is never cast.

The period between the egg-laying and the emergence of the adult insect is short: 5-7 generations may be produced within one summer. One female House Fly can produce more than 5,000,000,000,000 flies by autumn if all the eggs can hatch and develop. The greater the number of House Flies the greater the spread of disease.

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