I finally got around to reading Dr. Potter’s Lessons from the Past in PCT. (The online magazine article has great photographs.)
I wish I’d read this sooner but, in any case, Dr. Potter has a small aside that we should notice:
During the 1930s and ’40s, bed bugs became a community-wide problem like rats and mosquitoes. Infestation was worse in poorer, overcrowded neighborhoods, although wealthy households had problems as well. Besides being introduced on infested items, the bugs sometimes moved from house to house, escaping through exterior windows and doors and traveling along walls, pipes and gutters. A similar observation of bed bugs traveling outdoors between infested adjacent buildings was recently made by a pest control firm (Permakil) in Cincinnati.
Emphasis added.
Plain walking bed bugs.
Hmm. Lots of questions. Walking can kill bed bugs that are starved (Mellanby, 1938), so do they set off on these excursions fully fed? Just how far can they go? Because so little is known about this subject, we don’t know how unusual this may be. Does it help explain the spread of bed bugs on neighborhood blocks on this map a little?
In general, active dispersal is usually dismissed or de-emphasized in the literature and certainly in the press reports of the last decade.
Usinger, for example, in the Monograph of Cimicidae (1966):
While a certain amount of dispersal is incidental to active search for a host, especially with bed bugs in apartments and hotels, most dispersal is passive.
We hear plenty about travelers and their suitcases and unfortunate hotel stays and about people “introducing” bed bugs to their homes with used furniture and even—whenever a handy explanation for treatment failure is called for—people “reintroducing” bed bugs.
But in multi-unit housing in densely populated cities, like ours, active dispersal has to play much more of a role. While the dragging of infested furniture through the hallways and stairs and people visiting each other are surely ways to spread bed bugs between apartments in a building, I’d bet that most of the spread is really bed bugs walking from one apartment to another through walls and pipes. That they might also venture for a stroll outside and travel to the building next door is just not something I’m prepared to be surprised about.
And yet there is so little known about how this happens.
If we go back to those interesting 30s and 40s, to C.G. Johnson, author of The Ecology of the Bed-Bug, Cimex lectularius L., in Britain—published in 1941 as the culmination of 5 years of bed bug research paid for by the Bed-Bug Infestation Committee of the UK Medical Research Council—we see that very interesting experiments were designed to study the movement of bed bugs (more on those another day) but that of
the possible effects of population density and competition for host and space, or of migration; of these problems nothing of worth has been published. While the population is comparatively small (i.e. some hundreds of bugs in a room) these factors are perhaps not of prime and direct importance in the subsequent happenings to a population. But as the available harbourages within the room are occupied and new ones are sought farther afield, the success in finding a host without much waste of time must enter into the story. Of these problems, however, nothing is known either in the relationship to the general ecology or as specific and isolated problems.
This is what I am most interested in. For me, though I do not underestimate passive dispersal, the spread of bed bugs in our city is essentially a matter of bed bugs spreading from one poorly controlled apartment infestation to a second, adjacent apartment. An inquiry into the mechanisms behind this unexamined problem is the kind of research I would most like to see.
In the meantime, the best we can hope for is that control can be achieved with the automatic inspection and monitoring of apartments and spaces adjacent to an infestation. Before the bed bugs start walking. But it will take a great deal of education to make landlords, tenants, and pest control providers understand this priority.
Cited:
- Mellanby, K. 1938. Activity and insect survival. Nature. 141: 554 doi:10.1038/141554a0
- Usinger, R. L. 1966. Monograph of Cimicidae (Hemiptera, Heteroptera), The Thomas Say Foundation, Volume VII.
- Johnson, C. G. 1941. The ecology of the bed-bug, Cimex lectularius L., in Britain. J. Hygiene 41: 345–461
These pages may be of related interest:
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