What parts of the room do bed bugs prefer in historic houses?

About a year ago I was given the privilege (and I mean that sincerely) of treating a severely infested room in a 100 year old rooming house during a gutting/renovation process. The room was located in a corner of the second floor with two exterior walls and two interior walls. The home was a typical balloon framed structure with rough cut 2×4 fir lumber and lathe and plaster finishing.

The bed was simply a mattress on the floor which, in my experience, results in the the vast majority of the bugs leaving the mattress and harbouring in other areas of the room. My suspicions were confirmed when we installed glue board / climb up interceptor combination traps under a newly installed bed frame and found hundreds of bugs trapped upon later inspection. The number of bugs caught inspired the landlord to gut the room to find the bugs.

Evidence of several colonies was discovered in the gutting process. Firstly an electrical plug directly beside the mattress (on an inside wall) was almost black with bug excrement so I expected to find a very large colony in and around the plug. Upon demolition it was discovered that there was very little bed bug activity in that area. There was a small amount of spotting on the metal plug box and almost nothing in the rough cut studs and lathe and plaster – interesting! In other homes we have found massive amounts of harbourage on smooth cut lumber inside walls and on the back side of dry wall but it appears that the bugs did not like the furry nature of the rough cut fir lumber nor the rough plaster. Even the wooden lathe which was slightly smoother than the fir studs had little evidence of bug activity.

Next we removed the historic 8 inch fir baseboards with quarter round finish. Interestingly enough the vast majority of the harbourage in the baseboards was located on the two inside walls. The outside walls (poorly insulated), I am speculating, was subject to temperature extremes in both winter and summer and therefore pushed the bugs to the inside walls where the temperature was more even. Another interesting pattern was the bugs were located only in the quarter round on the outside walls while the interior walls had bugs behind the baseboard proper.

We then removed all the lathe and plaster and again discovered very little evidence of bed bugs. That is when we hit the mother lode – the door frame on an inside wall. It seems the vast majority of the bugs in the suite came from that location. However, once again, the harbourage was located on the smoother portions of the frame itself and nothing was located on the lathe and plaster or the fir studs.

I very much appreciated the opportunity to observe this demolition. It helps me anticipate where bugs are in future cases of historic homes.

If others have been involved in this type of demolition I would greatly appreciate feedback. I would like to know if the bugs we found in this setting is typical.

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