免费av毛片,日韩av高清在线播放,97国产精品最好的产品,欧美成人免费一区二区三区,神马午夜一区,曰河南少妇对白视频,欧美自拍视频

媒體英語會帶大家一起學(xué)習(xí) BBC 撰稿人在報(bào)道世界大事時(shí)常用到的單詞和短語。

科學(xué)家可能已找到對付臭蟲（又稱床虱）的辦法。這類昆蟲非常難控制，不過近期的科研結(jié)果有希望幫助科學(xué)家們研制出一系列新的、更有效的控制這一害蟲的方法。請聽來自 BBC Rebecca Morelle 的報(bào)道：

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.