A survey of an empty granary was undertaken to assess the size and composition of itsinsect fauna, and the possible importance of such insects as a source of infestation of stored goods. The most important feature of the building in this connection was the presence of boarded-up cavities in the walls.
Samples were taken at random from behind all walls, from parts of the grain-distributor system, and from certain other areas.
Many grain pests were found associated with the residues. In the wall cavities large populations had been built up, reaching in one case over 2,000 insects in the food material behind a foot length of wall (the average concentration over all cavities examined was 266 insects per foot of wall).
The largest populations were behind the north and south walls and, in general, the numbers of insects increased on descending the warehouse. The difference in size of population of the different walls and stories depended largely upon the volume and quality of the débris present in the cavities. The increase in numbers was due to increase in number of species and to increase in individuals of some species.