P6
Here in the United States, before agricultural activities destroyed the natural balance, there were great migrations of Rocky Mountain locusts (Melanoplus spretus) . Great migrating were often destroyed; the worst years were those from 1874 to 1877. One of these migrating 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 heights. 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 forms arise as 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 circumstances should become favorable.
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activity : n. 活动,动作,活力
destroy : vt. 破坏,毁坏,消灭
balance : n. 平衡,差额;vi. 平衡,相等;vt. 称,权衡,比较,抵消,使平衡,结算;资产平稳表
migration : n. 移民,移往,移动
locust : n. 蝗虫,蚱蜢,蝉
migrate : vi. 移动,移往,随季节而移居;vt. 使移居
swarm : n. 群,大群,蜂群;vi. 群集,聚集一块,云集,爬树;vt. 挤满,爬(树)
estimate : n. 估计,判断;vt. 估计,评价,判断;vi. 估计
contain : vt. 包含,容纳,容忍;vi. 自制
Nebraska : n. 内布拉斯加州,(美国中西部的一州)
against : prep. 反对,靠,倚
airborne : a. 空运的,空中传播的,空降的
convection : n. 传送,对流,对流
current : n. 涌流,趋势,流;a. 流通的,现在的,当前的,最近的
plague : n. 瘟疫,麻烦,灾祸;vt. 折磨,使苦恼,使得灾祸
situation : n. 情形,境遇,位置
serious : a. 严肃的,认真的,重要的,严重的
original : a. 最初的,原始的,有创意的;n. 原物,原作
constitution : n. 组织,宪法,体格
document : n. 文件,公文;vt. 证明,为...引证;n. 文档
grasshopper : n. 蚱蜢,蝗虫
phase : n. 时期,局面,阶段;vt. 使调整相位,逐步执行,实行
lesser : a. 较少的,较小的,次要的
common : a. 通常的,共同的,通俗的,公共的
respect : n. 尊敬,尊重,关心;vt. 尊敬,注意,遵守
resemble : vt. 相似,类似,象
relative : n. 亲戚,关系词;a. 有关系的,相对的,比较的
region : n. 区域,地方,地区,范围,区,领域,层
arise : vi. 站立,出现,起来
crowd : n. 群众,一伙;vt. 拥挤,挤满,挤进
climatic : a. 气候上的
factor : n. 因素,因数,代理人
migratory : a. 迁移的,流浪的
adaptation : n. 改编,适应,改编成的作品
bring : vt. 带来,产生,促使,提出;vi. 停下
dispersal : n. 散布,传播,分散
fortunately : ad. 幸运地
species : n. 种,类,外形
occur : vi. 发生,想到,存在
outbreak : n. 爆发,暴动
reason : n. 理由,原因,理智,理性,道理,前提;vt.说服,推论,辩论;vi. 推论,劝说,思考
destructive : a. 毁灭性的,破坏的,有害的
circumstance : n. 环境,状况,事件
favorable : a. 有利的,赞许的,良好的