09 May Observations of how bed bugs climb up and down

We have already noted that bed bugs do not like to climb down slippery surfaces. But will they climb down other surfaces? The answer is mixed.

I set up a piece of cardboard in the experiment pan and noted that the bugs climbed the middle of the cardboard readily but tended to climb down the edges of the cardboard. The bugs would occasionally climb down the middle part of the cardboard quite easily but the edge was the definite favourite.

I then set up a piece of construction grade plywood shaped like a square climb up interceptor. The surface of the plywood was not nearly as uniform as the cardboard. Once again the bugs climbed up easily enough but tended to walk on the top edge of the plywood in a manner similar to the plastic interceptor. The bugs would occasionally climb down into the plywood interceptor easily enough but tended to spend more time on the top edge. As time went on the bugs became more familiar with the device and were a little more apt to climb down inside.

I then put a piece of plywood with small 1/8 inch vertical ridges in the middle into the experimental pan. The bugs definitely preferred to climb down the ridges but would also occasionally climb down the middle part as well. All told it appeared that climbing down the middle of anything was not the preferred mode of travel. If a narrow vertical ridge was available the bugs preferred to climb down in that place.

An interesting observation on the rough plywood is that the bugs occasionally tripped going down the plywood and fell off the structure. I never noticed any falling on the cardboard. The bugs never tripped on any substrate while going up. I would speculate that, because the bed bugs feet are shaped like backward facing hooks, climbing up is easier. While going down the hooks are facing the wrong direction and can not grab traction as easily and are more apt to fall – especially on uneven surfaces. Thus the bed bug’s preference for climbing and aversion to going down.