In representing that the house-fly exceeds the lesser house-fly in numbers in the proportion of twenty or thirty to one, it must be borne in mind that the occurrence of the latter varies widely—casually according to the locality, and temporarily according to the time of the year, being more commonly observed when and where the other kind is scarce. The lesser house-fly has summer broods at longer intervals than has the common house-fly. Towards the end of the summer its last brood hibernates in the puparium, and emerges as early as the end of March or early in April, whilst the common house-fly is not usually observable until a later date, although it is credited with more generally braving the dangers of attempting to hibernate in the imago stage. My attempts to test the capability of the house-fly by aiding October and November flies to hibernate invariably terminated in the creature's death long before springtime. However, it is very apparent that under the shelter and encouragement of warm winter environments in towns, amidst restaurants, bakeries, large hotels and certain factories, as well as and even more than in mews, adult flies of the latest autumn broods can, to some extent, survive mid-winter with very little or no prolonged hibernation. CHAPTER III SOME OTHER FLIES AND THEIR DIVERSE HABITS Just as the common "house-fly" and the "lesser house-fly" are often in error regarded as the same species with an insignificantly small difference of size, so the identity of each in turn may be confused with several other species which are not uncommon, but they are all normally outdoor flies. The chief of these is the excessively common stable-fly, _Stomoxys calcitrans_, whose generic and specific designations are well given, for they mean "sharp-mouth," "kicking," the latter word denoting the action of the tormented horse; it has a long, thin, stiff, skin-piercing, shining black trunk, furnished with two lancets. It is an eager blood sucker. In size and colour it rather resembles the house-fly, but anyone who is keen sighted will recognise it at once by its bayonet-like trunk, held projecting prominently in front of its head. It is much addicted to basking outdoors on sunny walls, but on the approach of darkness or of inclement weather it will occasionally seek shelter indoors. Its wing pattern rather resembles that of the common house-fly, as has been previously explained. Round about dairy farms _Hæmatobia stimulans_, a fly slightly smaller than the stable-fly, with a striped thorax and a blood-sucking trunk, will often leave the cattle to assail humanity. A still smaller, somewhat hairy, muscid type of fly, _Lyperosia irritans_, is also a common aggressor of oxen throughout the summer.