Bed bugs are a gregarious bunch and often prefer to stay together in a group. But if a harbourage becomes too full the bugs start moving elsewhere. The typical pattern is the bugs move to an entirely new area nearby. And if the infestation is established enough most of the bugs abandon the earlier harbourages.
As an example I was involved in a highly infested suite where all the baseboards and door frames were removed and heated. The baseboards near the sleeping areas showed massive spotting but very few bugs. The bed, considering the severity of the infestation and amount of spotting, contained few bugs. The bugs had moved on to new homes further and further away from the host. And when we set up glue board traps under the bed legs we caught 500 bugs a day for two weeks straight. It is interesting that the bed and nearby areas had few bugs and still we caught 500 a day.
Bed bugs also abandon harbourages when they are chemically self treated. The bugs, instead of being in the ordinary places near the sleeping host, end up in crazy places like clocks and under the microwave in the kitchen. Self treatment, in some ways, mimics a more severe infestation. Either way, whether the established harbourages are empty because of the severity of infestation or the abuse of chemicals, I know I have a substantial project ahead of me.