英语听力精选进阶版 7286（在线收听）

科学家可能已找到对付臭虫（又称床虱）的办法。这类昆虫非常难控制，不过近期的科研结果有希望帮助科学家们研制出一系列新的、更有效的控制这一害虫的方法。

They feast on our blood while we sleep - leaving itchy, red welts as their calling card. Bedbugs are an insect that many would like to see the back of. But in North America, Europe and Australia, infestations are on the rise - and our insecticides are losing their bite.

Researchers at the University of Kentucky in the US have found 14 genes associated with resistance to these chemicals. They're causing a number of biological changes in the bedbugs. These include the development of a thicker skin that stops the poisons from penetrating and mutations within the insects' bodies that prevent the toxins from hitting the nervous system.

The genes linked to these changes are active in the insect's tough outer shell - creating a formidable first line of defence. These findings could help scientists to develop new insecticides that could either turn these genes off or bypass the pest's molecular shields.

But until these substances are developed, exterminators are having to resort to more primitive tactics.

Quiz 听力测验

True or False? The number of bedbugs is rising in North America, Europe and Australia.

True. Infestations are on the rise in North America, Europe and Australia.

True or False? Researchers in the US found 14 genes inside bedbugs that are resistant to insecticides.

True. Researchers at the University of Kentucky in the US have found 14 genes associated with resistance to the insecticides.

Which biological changes are caused by the 14 insecticide-resistant genes found in the bedbugs?

The changes include the development of a thicker skin that stops the poisons from penetrating and mutations within the insects' bodies that prevent the toxins from hitting the nervous system.

Why do bedbugs have a formidable first line of defence?

Because the genes linked to the biological changes are active in the insect's tough outer shell.

Glossary 词汇表

itchy 发痒的，瘙痒的

welts 红色肿块

calling card （留下来过的）标示、证据

infestations （害虫）大批出没、猖獗

insecticides 杀虫剂，杀虫药

penetrating 渗透，进入

mutations （基因）变异

toxins 毒素

formidable 强大的，难以对付的

exterminators 消除有害动物（如害虫）为职业的人