Lab foraging versus real life foraging

Over the years I have recorded bed bug bed bug behaviour on various substrates and apparatuses many times. One thing I always noted was that the foraging behaviour was always quite sedate when I inspected the experiment in the morning but would quickly ramp up with my presence. Therefore I concluded that I was not very good at eliciting foraging in my lab. I assumed that foraging behaviour was much more vigorous in real life settings.

I decided to test this hypothesis. I purchased two identical teflon pans and placed one in my lab under camera and the other under my bed with a camera. I placed a Climb Up Interceptor in each pan because they are known to have considerable repellency issues. I wanted to see if the Interceptor under the bed, in identical lab like conditions, caught more bugs due to more vigorous foraging behaviour.

I placed 25 starving adult bed bugs that had been acclimated to a paper harbourage into each teflon pan beside the interceptor. In the lab I released 200ml per minute of co2 directly on top of the pan and a heat source at body temperature. The lab was lit with a cloth wrapped nite light to enable the camera to record but dim enough to simulate a night phase when the overhead light was turned off.

I built a higher platform for my bed to accommodate the camera (same height as the lab) and placed a cloth wrapped night light under my bed to allow the camera to record. I could not replicate the amount of light in the lab exactly in my bedroom because my windows, despite drawn shades, allowed additional street lighting into the room. I ensured the windows remained closed and the heating system was off to ensure that air movement remained similar to the lab. The temperature in both the lab and bedroom was roughly comparable. The pan of bugs was placed on the floor directly under my upper torso. All things considered I thought I had created a reasonably fair experiment.

I was absolutely convinced that the bedroom experiment would catch more bugs before I went to bed and was shocked to discover that the lab caught twice as many bugs. The lab had caught 11 of 25 bugs while my bedroom had caught just 5. Furthermore there were 5 bugs under the lab interceptor and only 1 or 2 under the bedroom interceptor. The original paper harbourage in the lab only had 9 bugs while my original paper harbourage in the bedroom contained 18 or 19. There was movement in and out of the harbourage at night but in the end most of the bugs in the bedroom returned to their harbourage.

Interestingly the activity level on both experiments quickly ramped up when I inspected the experiments in the morning. In fact the bedroom experiment activity ramped up so quickly I could not quite tell if there was only one bug under the interceptor or two – the bugs started moving that quickly.

I learned that a lab with heat and Co2 is perfectly able to elicit foraging in a pan of bed bugs. I also learned that changes in the level of host cues in an occupied bedroom can elicit vigorous foraging just like inspecting an experiment in the lab. It appears it is the rapid changes in host cues, not the absolute amount of cues, that drives foraging. Future questions involve the level of foraging in a bedroom at different distances from the host.

Thanks to Richard Naylor for providing suggestions and  bedbugs for this experiment.   All deficiencies in the experiment are mine.

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