Richard Naylor’s PHD dissertation entitled “ecology and the dispersal of the bed bug” documented an experiment involving a very narrow but nine foot long experimental apparatus with lines of harbourage (like a really long mattress rib) extending the length of the apparatus. Bed bugs were placed at one end of the apparatus with a feeding station and a tank of co2 to act as the lure. Ten bed bugs were added to the feeding station end of the apparatus every day and it was documented where the bugs harboured over a period of time. An exit tube at the far end of the apparatus simulated a bed bug dispersing away from a known host. The results showed that bed bugs harboured further away from the host when harbourage near the host was restricted. Fascinating experiment.
The most interesting facet of the experiment for me was the observation that bed bugs further than 50cm from the lure did not feed as often as those bugs that were closer to the “host”. Naylor did not explore this phenomenon in any detail (he did suggest that the windy experiment room could have been a factor in not allowing bugs to home in on the source) as it was not the focus of his project but I think this behaviour is critical in understanding the bed bug.
I immediately recognized Naylor’s delayed feeding pattern observation in my own work with bed leg traps (of varying constructions) and severe infestations. Consider the following: When we begin work in larger infestations (the bugs are always further away from the host) we heat sterilize beds and couches and isolate them with interceptor or modified glue board traps when returned to the suite. The remainder of the suite is thoroughly chemically treated. Despite the careful treatment it is common to catch large numbers of bed bugs in the traps several weeks after the initial treatment (500 a day for two weeks straight in the most severe instance I came across). After the initial rush of bugs it is common to have the bugs slowly leak out of the various hiding places over a period of several months. If the tenant cooperates with laundry and bed isolation protocols we stop catching first instar bed bugs after a couple weeks because the new hatchlings can only survive a couple days without a blood meal (see previous post entitled “bedleg traps, first instars, and the measurement of success/failure in getting rid of bed bugs.”) Thereafter we only catch increasingly emaciated second instar or older bed bugs. The last bugs caught are often so emaciated they appear translucent.
In these instances we see that some bed bugs remained in their unknown harbourages and chose to forego a blood meal for several months. The lack of first instars tells us that these bugs were not feeding and were preexisting. This is the same behaviour that Naylor documented.
The same behaviour can be seen in my post entitled “field observations of bed bugs in starvation settings.” In this case the suite had been empty for 3 months and many bed bugs continued harbouring on the bed despite a viable host being available only 10 feet away in the next room. What this means is that some bed bugs will, in the absence of host cues, wait for several months without moving. If the bugs have harboured in an area that host cues can not penetrate (far away from the host) and the exterminator can not access it is a very big problem. The bugs slowly leak out of the walls to the great frustration of both tenant and exterminator.