Tiny hairs on the leaves of the kidney bean spike the legs of bed bugs. American researchers see a synthetic version of the leaves as a new means of combating the re-encroaching species.
Bed bugs have plagued people's lives for years by nesting between mattresses. They were gone for a long time, but lately they've been popping up more and more in European and American hotels. Unfortunately, it is a tough insect that is not so easily killed. Even insecticides are not very effective because of the resistance that the insects have developed against them. Scientists are now focusing on modernizing an age-old method.
Velcro tape
At the beginning of the 20th century, people in the Balkans would put the leaves of bean plants around their beds before going to sleep. Early in the morning the leaves were full of motionless bed bugs. The leaves were brought out and burned with bugs and all. In 1944, a scientist discovered that this method worked so well because the leaves are covered with tiny hairs. He thought that the critters got stuck in this, similar to how Velcro works.
A genius idea that was not acted upon for years. Insecticides such as DDT did their job, the bed bug plague seemed under control. But now that insects are developing more and more resistance and drugs like DDT are banned because of their toxicity and harmfulness to the environment, the leaf option doesn't seem so bad after all.
Kidney beans
So did Mike Potter of the University of Kentucky and Megan Szyndler and colleagues at the University of California, and they decided to make a synthetic version of the leaves. Real leaves dry out quite quickly and lose their effect. In the lab, the researchers studied the movement of the bugs on kidney bean leaves. By filming and photographing the bugs under a microscope, they saw that the final blow to the bugs was not the entanglement, but the fact that they were impaled by the hairs of the leaves. It only took a few seconds and a few footsteps for a bug to get stuck in the minefield of hairs. However, the insects could get entangled, but they always quickly freed themselves, after which an effective sting was never far away.
Fishing hooks
The bean hairs prefer to 'choose' the soft parts of the bug, such as the underside of its claws. As a result, the hairs look more like fish hooks than Velcro, the researchers write in their publication in Journal of the Royal Society Interface.
In itself, the discovery is not very special, since leaves do 'catch' more insects such as aphids. That is an evolutionary adaptation of the leaves. Coincidentally, the bed bug also falls into that trap and that is a nice bonus for us.
Hol is the key to success
The researchers therefore set to work with a mold of the surface of the leaves. The fake leaf looked exactly the same, had the same number of hairs with the same sharp points and the same thickness. One problem:they barely caught a bug. Why is not entirely clear to the scientists, but they think it is because the natural hairs are hollow and the synthetic hairs are not. This makes them stiffer so that they may simply bend away when a bug walks by. A natural hair, on the other hand, twists and bends around a bug until it finds the perfect sting spot. Synthetic hollow hairs may be the key to success and terrorizing bed bugs will soon be a thing of the past.