For at least a century, people in Balkan countries have had a trick for catching bed bugs that the rest of the world hasn’t picked up on: they spread bean leaves on the floor at night. When bed bugs travel across the leaves to feed on sleeping people, they become entangled and are unable to free themselves.
In the morning, well-rested sleepers gather up leaves and bed bugs and toss them on the fire. Good bye bed bugs.
Bed bugs and bean plants don’t typically hang out together, but other insects do trouble bean plants. Dr. Ken Haynes, coauthor of a report on entrapment of bed bugs by bean leaves, says that there must be “a pest out there the same size and geometry as a bed bug.”
The mechanism that traps bed bugs likely evolved to protect bean plants from their own pests.
How Do Bean Leaves Trap Bed Bugs?
Spurred on by the current resurgence of bed bugs worldwide, Haynes and colleagues are investigating just how bean leaves trap the bugs, and attempting to fabricate an identical trap using synthetic materials.
Using male bed bugs and kidney bean leaves, they documented what happens when a bed bug attempts to walk across the surface of the leaf.
Bean leaves have tiny structures called trichomes on their surfaces, which the authors describe as “analogous to barbless fishhooks in their mechanical action.” They don’t just wrap around an insect leg; they actually puncture the insect cuticle and hold the creature in place. Because there are many of these trichomes on the leaf, the bed bug is caught within seconds of stepping onto the leaf, and struggling typically results in more trhichomes piercing and holding their legs.
If the luckless bug does break free, there are more trichomes ahead to trap it again.