On this subject nothing useful can be said other than can be safely surmised from the known habits of the fly. The female has none of the attachment of the honey-bee to its hive and community; she is not moved by an instinct like that of the wandering bumble-bee in spring to found a colony; she is indeed very solicitous about the disposal of her eggs, but she is not impelled by any desire to place successive deposits in one locality. The lesser house-fly has proclivities similar to those of the common house-fly, but probably she travels less far afield although a little more inclined to outdoor life. Very little is known about most of the common outdoor sweat-flies. Some breed in dung, and may be many-brooded and otherwise resemble the house-fly in prolific increase; others are more consistently vegetarian in the larval stage and slower in development; and some are possibly even single-brooded, like certain foreign large sized flies which fortunately appear only for a few weeks of summer weather, for they have a curious semi-blood-sucking habit of feeding after or alongside the skin-piercing flies, and their suctorial mouths are capable of further inflaming wounds and carrying infection from one animal to another. The robust blue-bottle very closely resembles the house-fly in an inclination to spread the brood. Mature females, however, do sometimes show a slight temporary kind of "homing" instinct; having secured a cosy corner and a well sheltered retreat in a sunny wall, the occupant will battle for its possession, buffeting new comers. Some of the smaller filth flies and many of the fungus flies have their lives, in the imago stage, influenced and shortened by their extra early sexual maturity; the females are fertilised whilst newly hatched and their wings limp and unfolded. This fact accounts for our seldom seeing some kinds of these flies abroad except females; and these are never seen to indulge in dances, flirtations, and games of chasing and buffeting each other, after the manner of so many kinds of flies. They habitually fly low; nevertheless they travel very great distances, for, though short, their flights are incessant when searching for their special kind of food. The most disinclined to roam of all common flies is the stable-fly. None other is a more eager seeker of sunshine, but when basking on a sunny wall it seems unwary and sluggish; it is seldom to be seen far from where horses or cattle are stationed or stabled; however, it will make very long journeys hovering about a driven horse or reposing on the car. A plague of flies of local origin will not take many weeks of summer weather to spread, but it is generally observable that plagues of flies, like many other occurrences, are simultaneous co-incidences distributed over wide areas and at places remote from each other. CHAPTER VIII NATURAL ENEMIES AND PARASITES