The problem of bed bugs feeding during the day


I am assisting a local rooming house owner address a very severe infestation in one of his rooms. Several thousand bugs were caught in the glue board traps on first inspection after first treatment. After 3 treatments the number of bugs caught in the traps declined but I noticed a continuing abnormal number of first instars being caught suggesting the bugs were still feeding and laying eggs despite the bed being isolated.

Upon interviewing the tenant it was determined that he rarely left the suite and sat on a chair right beside the bed during the day. I therefore assumed that the bugs were feeding during the day when the tenant sat on the chair.

During initial treatments I left a couple random climb up interceptors under the bed to gather live bed bugs for experiments. My regular treatments always involve treating the area under the bed with residuals so the bugs that fell into the interceptors survived despite traversing the residual. That was impressive as the carpet fibres impart the residual directly to the bed bugs body much faster than a hard floor could. There must be at least some degree of pyrethroid resistance in this batch of bugs. And if the the tenant continued to sit beside the isolated bed I would not be able to impart a lethal dose to the bugs as they simply walked back and forth to their unknown harbourages.

The landlord decided to place a piece of ¾ inch plywood on the floor beside the bed on which the chair could sit. Under this plywood we placed more glue board traps. Now the tenant is isolated both on or off the bed. We inspected the room one day later. Interestingly there were 15 bugs caught under the bed and at least 14 under the plywood (could not check all traps perfectly under the plywood due to awkward positioning of the traps). This means the bugs were approaching the tenant for feeding purposes equally during night time and day time – interesting.

To understand this unusual behavior there are a few puzzle pieces which could offer some explanation to this story. Firstly the tenant is sitting all day right beside the bed which would cause at least some bugs to chase the tenant during the day.  In fact there were several hundred eggs on the bottom side of the computer chair – obviously no one slept on that chair.    It is normal bed bug behavior.

Secondly the landlord has been using the unmodified glue board traps on carpet which does have some repellency. He does this because the traps are easier to manufacture. We overcome this deficit with regular applications of residuals which then kills the bugs that are repelled. But in this case the residual was less effective due to resistance. Could it be that there was more day time activity because some bugs were being repelled at night? Probably. Furthermore there appeared to be increased activity in other rooms which was unusual. Would a resistant repelled bug be more likely to look for food elsewhere? Possibly. Very interesting case.

We have now placed modified glue boards under the bed (less repellency) and left the ordinary glue boards under the plywood. When we reinspect it will be interesting comparing the bug counts between the two traps types. I very much enjoy this kind of work – a great learning opportunity.


Update December 6, 2014

The plywood /glue board trap was placed under the chair on November 18, 2014. The suite had just been treated with Tempo 25673 @.1%. A closet at the foot of the bed had never been emptied (non compliance) so we emptied it ourselves and treated that area.

On November 19 we counted 15 bugs in the bed traps and 14 in the chair traps.

On November 25 we counted 10 in the bed traps and 34 in the chair traps

On December 6 we counted 17 in the bed traps and 99 in the chair traps.

In percentage terms we see an increasing amount of bugs being caught in the chair/plywood/glueboard traps representing a highly significant amount of day time feeding. How do we explain this behaviour?

I hypothesize the following: Bed bugs have within their populations a wide variety of behaviours. For example on one occasion I placed a number of bed bugs in my experimental pan and gave them an excellent harbourage in which to hide. I let the bugs starve for a few weeks with the light on at all times and the room was devoid of all host cues. Very little activity was noted during this time via the video recording. I then entered the room and turned on the Co2 to entice them over an experimental poisoning apparatus. A large percentage of the bugs entered the arena quite quickly and died very quickly but some refused to exit the harbourage. I let the experiment run overnight with Co2 and again the bugs in the harbourage refused to exit. I attribute this behaviour to the full lighting conditions. What we see here is that different bugs have different levels of risk aversion. Some readily forage during light conditions and others are highly reluctant. It is almost like the bugs have personalities.

Therefore I propose that the glue board bed leg traps selected out the risk averse bugs over a period of several weeks. Day time feeding was still occurring but only with the adventurous bugs (they had avoided the bed leg traps). When the plywood / chair traps were added it appeared that the bugs were mostly feeding during the day. But this does not account for the several thousand bugs that were removed from the room earlier with night time feeding (bed leg traps) only. In overall percentage terms the bed traps caught the vast majority of the bugs.

We inspected all the other suites and the earlier increase of bugs in other areas has dissipated and a return to normal declining patterns was noted. I can’t explain the temporary increase. The first instar population is crashing suggesting we are on our way to success here.

When I first installed the modified glue boards I expected them to outperform the non modified versions by a large margin as they are demonstrably superior. I was wrong. Other issues were at play here that messed with my predictions.

All told I am very impressed with the performance of the plywood/chair/day time feeding trap method.


Update December 8, 2014

When we noticed the large numbers of bugs being caught under the chair in the rooming house we decided a second suite in another building could benefit from a similar treatment. This case is not quite as cut and dried with a clear delineations with “night time” and “day time.” The tenant suffers from a sleep disorder resulting in no consistent schedules. Still, whatever sleep is obtained is on the bed while awake hours are spent at a computer about two feet away from his bed. The tenant stays home in his room most of the time going between bed and computer.

We began standard chemical treatments and isolating the bed with non modified glue board traps. The first inspection at 3 weeks showed about 2000 bed bugs in the glue boards. The tenant complained of increased activity at his desk and that made sense to me as the bugs become more aggressive after walking through residuals. The second inspection at 6 weeks showed about 1000 bed bugs in the glue boards and we added the plywood / glue board trap under the desk/chair with non modified glue traps . We returned two weeks later for an inspection and found 63 bed bugs under the bed and 107 under the computer chair. Once again we see the computer chair traps outperforming the bed traps but only after we first removed 3000 bugs via the bed traps. The vast majority of the bugs were caught under the bed but a signifiant number of day feeders remain a problem.


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