Questions 36-40 are based on the following passage.
Here in the United States, before agriculture activities destroyed the natural balance, there were great migrations of Rocky Mountain locusts (蝗虫）(Melanoplus spretus). Great migrating hordes of these insects once darkened the skies on the plains east of the Rockies where crops were often destroyed; the worst years were those from 1874 to 1877. One of these migration swarms was estimated to contain 124 billion locusts. During another migration in Nebraska it was estimated that the swarm of locusts averaged half a mile high and was 100 miles wide and 300 miles long. Usually, these swarms take off from the ground against the wind, but, once airborne, they turn and fly with it. Warm convection currents help to lift them, often to great height. During the great locust plagues the situation in Nebraska became so serious that the original state constitution had to be rewritten to take care of the economic problems. The new document was known as " The Grasshopper Constitution." It is now believed that these locusts were a migratory form or phase of the lesser migratory locust, which is still common there. In this respect, the North American migratory locusts resemble their African relatives. In both regions, the migratory a result of crowding and climatic factors. Migratory forms are apparently natural adaptations which bring about dispersal when locust populations become too crowded.
Fortunately for our farmers, the migratory form -- the so-called spretus species -- no longer seems to occur regularly, although there was a serious outbreak as late as 1938 in Midwestern United States and Canada. Actually, there is no reason why the destructive migratory form might not again appear if circumstance should become favorable.
36. Which of the following is the best title for the passage? A. the Kinds of Locusts B. the life style of Locusts C. Migratory Locusts in the United States D. the life Cycle of Locusts
37. According to the passage, the worst destruction by locusts in the plains area east of the Rockies occurred during the ______. A. eighteenth century B. early nineteenth century C. late nineteenth century D. twentieth century
38. It can be inferred from the passage that the state constitution of Nebraska was rewritten in order to ______. A. provide for a regular census of the locust population B. make the constitution more understandable to the public C. encourage farmers to leave the estate D. solve difficulties that resulted from loss of crops
39. According to the passage North American and African migratory locusts are similar in that ______. A. their destruction activities occur only in plain areas B. they always travel toward mountainous regions C. they are both mentioned [in state constitutions D. climates affect their development
40. What does "horde" (line3, Para. 1) probably mean? A. tribe B. large group C. horizon D. nestle
a result of crowding and climatic factors. Migratory forms are apparently natural adaptations which bring about dispersal when locust populations become too crowded. 
