Infests many species of small rodents, though Holland (1985) believed the meadow vole, Microtus pennsylvanicus, to be the primary host. This host is abundant, at times, very abundant throughout most of NT, though M. asio megacolpus is known only in the western portion of its host's range in the territory. The range of this flea may include eastern NT, and perhaps even western NU. The small number of occurrences is almost certainly a reflection of insufficient collecting effort rather than an indication of its true abundance. More data are needed before an accurate rank can be assigned to this subspecies of flea in NT.