2. 职称英语
  3. A man-made chemical that attracts male gypsy moths by duplicating the natura

A man-made chemical that attracts male gypsy moths by duplicating the natura

游客2025-04-25  41
问题     A man-made chemical that attracts male gypsy moths by duplicating the natural attractant of female gypsy moths has been patented as No. 3,018,219.
    Dr. Martin Jacobson of Silver Spring, Md., assigned patent rights to the U. S. Government as represented by the Secretary of Agriculture. The chemical can be used to detect gypsy moth infestations, as well as to control the insects.
    The gypsy moth does serious damage to forest and shade trees in New England and eastern New York State. The caterpillars, or larvae, of gypsy moths eat the leaves of trees, often causing death by a single attack. Losses of hardwood trees have been estimated at tens of millions of dollars from a 20-year study.
    Gypsy moths were prevented from spreading to other U. S. forest areas by using the natural attractant of the female to detect infestations, then spraying with chemicals such as DDT to kill the insects.
    Since the lure could previously be obtained only by clipping the last two abdominal segments of the virgin female moth, extracting the segments with benzene and then processing to stabilize the chemical, the procedure was expensive. Another difficulty was that, as the gypsy moth population declined, it became increasingly hard to obtain the females needed for lure production.
    Dr. Jacobson overcame both these difficulties by discovering a synthetic method for making the female’s attractant chemical. The chemical is known as 12-acetoxy-l-hydroxycis-9- octadecene. It is so potent that the fraction of a drop produced by the female is 200,000 times more than the amount needed to catch a mate. The synthetic chemical is also very powerful--it works in amounts about equivalent to one drop in a box car.
    The flightless female gypsy moth mates only once a year and, as soon as she does, an enzyme switches off production of the sex attractant. The winged male, however, call mate several times and it is because of this that the chemical is being used for pest control.
    By using a mixture of attractant and DDT in traps lined with a sticky substance, enough males can be caught to reduce the gypsy moth population substantially. [br] The damage done by gypsy moths to trees in New England and New York is done by ______.
选项 A、only the male moth
B、only the female moth
C、a substitute female attractant
D、caterpillars
答案 D
解析 舞毒蛾给新英格兰和纽约的树木造成的危害是由毛虫造成的。根据第三段第二句，舞毒蛾的毛虫或幼虫吃树叶，往往通过一次袭击就导致树木死亡。
转载请注明原文地址:http://tihaiku.com/zcyy/4053742.html
相关试题推荐
随机试题
最新回复(0)