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IS THE YEAR WHEN A LOCUST PLAGUE ATE ALL OF THE CROPS AND LEFT

CLOSE TO 100,000 PEOPLE DEAD IN NORTH AFRICA.

Locust Plague

The species that causes plagues of locusts on the African continent is the desert locust, Schistocerca gregaria. This insect belongs to the Acrididae family and to the order Orthoptera The locust has an elongated body, about 2 to 3 inches (6-8 cm). The locust modifies its behavior and appearance in response to environmental conditions. It also feeds on most crops, on wild plants, and on some trees, such as sapwoods.

How Does the Plague Start?

^^ When rainfall creates the appropriate conditions for their reproduction, locusts that live in desert or semiarid regions multiply at a dizzying rate. If the species is in the solitary phase, it is harmless, but when rains come and bring about abundant plant life, the locusts gather together, increasing their reproductive capacity. At that point the locusts mutate into their gregarious phase and change not only their movements but also their morphology. Each female is capable of laying 120 eggs, so that an area of 2.5 acres (1 ha) can breed up to 600 million locusts, which will gather into mile-long swarms that travel large distances in search of food.

• SUMMER BREEDING AND

CONSECUTIVE MIGRATION ZONE

Locusts reproduce at a rate of millions at a time, and they devour all of the food that lies along their path. The map shows the two main summer breeding zones.

WINTER AND SPRING BREEDING AND CONSECUTIVE MIGRATION ZONE

The swarm of locusts moves to other zones in order to reproduce and feed itself. Afterward, during winter and spring, the locusts retrace their path, and the cycle starts over again.

Pest Control

The countries victimized by locusts defend themselves by chemical or biological means on the land or from the air. Pesticide use is restricted, and pesticides can be used against a swarm only when it has begun to form, because misapplication of a pesticide can affect other insects and crops. The locusts are controlled by the application of poisonous bait and by plowing up the ground to bury the eggs.

LOCUSTS IN ANTIQUITY The devastating effects of locusts can be traced back thousands of years. Locusts were known as one of the seven plagues of Egypt.

conditions. As the use of drugs increased, the medicinal use of leeches was gradually forgotten. In the 1980s, however, leeches once again began to be used in microsurgery and reconstructive surgery. •

Illustration of a chapter of the Decameron by Boccaccio, which shows the use of leeches to treat illnesses. The patient is the Roman emperor Galerius, who ^H has a disease that causes the putrefaction ■■■•J1 of the body. The three jr v doctors, aghast at his condition, r^k have put leeches Tl on his body to tV 1 cure him.

SUCKING MOUTlT

Once the leech's mouth is placed on the body, it begins to suck blood at the rate of one cubic inch every 2 hours and 40 minutes.

TWISTING

The sections of the leech's body allow it to flex and assume different postures.

Ancient Uses

FRANÇOIS J.-V. BROUSSAIS (1772-1838)

French doctor who believed that most diseases were caused by the inflammation of the intestines and who preferred bleeding with leeches as a cure. His opinion became so popular that in 1833 he had 40 million medicinal leeches imported into France.

^^ The use of leeches in ^tf medicine goes back over 3,000 years. In Greece, Rome, and Syria these worms were used to remove blood from many areas of the body. It was believed that bloodletting, or phlebotomy, could cure anything from local pains to inflammation and mental disease. In the 18th and 19th centuries, leeches were sold in European pharmacies, and they became very popular in the therapies of the day, especially in France.

TYPES OF LEECHES

Leeches are classified according to how they feed. One group of leeches includes animals whose pharynx has no teeth and cannot be turned outward. A second group includes leeches whose pharynx is toothless but can be turned outward like an elephant's trunk, projecting out of the leech's mouth, and can be inserted into the host's soft tissues. The third group includes highly specialized leeches in which the pharynx cannot be turned outward but is armed with three chitinous jaws with serrated edges.

EUROPEAN MEDICINAL LEECH

This leech is used in medicine to treat the congestion of veins in reconstructive and plastic surgeries. The bite causes a hemorrhage where the tissue graft is placed, imitating the circulation of the blood.

LEECHES

There are 600 species of leeches. Leeches usually have 34 segments, but they can have 17 or 31. They live mainly in freshwater environments, but a few live in saltwater, and some have adapted to life on land in warm, damp places.

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