DISTRIBUTION AND CONCENTRATION 51 



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-bloodsucking 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, buffet- 

 ing 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 arc 

 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 



