問題詳情

Locusts are certain species of short-horned grasshoppers in the family Acrididae thathave a swarming phase. These insects are usually solitary, but under certain circumstancesthey become more abundant and change their behavior and habits, becoming gregarious. Notaxonomic distinction is made between locust and grasshopper species; the basis for thedefinition is whether a species forms swarms under intermittently suitable conditions.In the solitary phase, these grasshoppers are innocuous, their numbers are low, and theydo not pose a major economic threat to agriculture. However, under suitable conditions ofdrought followed by rapid vegetation growth, serotonin in their brains triggers a dramatic setof changes: they start to breed abundantly, becoming gregarious and 15 (looselydescribed as migratory) when their populations become dense enough. They form bands ofwingless nymphs which later become swarms of winged adults. Both the bands and theswarms move around and rapidly strip fields and cause damage to crops. The adults arepowerful fliers; they can travel great distances, consuming most of the green vegetationwherever the swarm settles.Locusts have formed plagues since prehistory. The Ancient Egyptians carved them ontheir tombs and the insects are mentioned in the Iliad, the Bible and the Quran. Swarms havedevastated crops and been a contributory cause of famines and human migrations. Morerecently, changes in agricultural practices and better surveillance of locations where swarmstend to 16 have meant that control measures can be used at an early stage. Thetraditional means of control are based on the use of insecticides from the ground or the air, butother methods using biological control are proving effective.Swarming behavior has decreased in the 20th century, but 17 modern surveillanceand control methods, the potential for swarms to form is still present, and when suitableclimatic conditions occur and vigilance lapses, plagues can still occur. Locusts are largeinsects and convenient for use in research and the study of zoology in the classroom. They arealso edible insects; they have been eaten throughout history and are considered 18 inmany countries. The word “locust” is derived from the Vulgar Latin locusta, meaning locustor lobster.
15.
(A) aggressive
(B) independent
(C) nomadic
(D) superfluous

參考答案

答案：C
難度：適中0.5
統計：A(0),B(0),C(0),D(0),E(0)

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