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.