It's pretty clear that mite invasion spikes in late summer, coincident with the increase in "robbing behavior."

Population Density and Social Pathology
When a population of laboratory rats is allowed to increase in a confined space, the rats develop acutely abnormal patterns of behavior that can even lead to the extinction of the population.

> In the celebrated thesis of Thomas Malthus, vice and misery impose the ultimate natural limit on the growth of populations. Students of the subject have given most of their attention to misery, that is, to predation, disease and food supply as forces that operate to adjust the size of a population to its en­vironment. But what of vice? Setting aside the moral burden of this word, what are the effects of the social behavior of a species on population growth -- and of population density on social behavior?

Calhoun, John B. "Population density and social pathology." Scientific American 206.2 (1962): 139-149.

PLB

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