IDENTIFICATION OF HOUSE-FLIES 9 



cuting and torturing flies ; this last group, strange to 

 say, are absolutely destitute of any mouth and feed 

 only in the maggot stage. In many cases, however, 

 it happens "that the males and the females differ in 

 feeding habits as well as in colours and markings, 

 whilst only their patterns of wing-veins and some 

 less prominently apparent features are constant in the 

 two sexes. These circumstances discountenance the 

 above grouping. 



Again, if we tried to group our flies with adequate 

 regard to their very diverse habits of life, in the larval 

 stage as well as to their subsequent metamorphoses, 

 we should find that these are details which are obscure 

 and in many cases unknown or imperfectly recorded. 

 However, after much study and many revisions, a 

 scientific classification has been contrived based upon 

 the minutely differentiated characteristics which are 

 technically explained in the Appendix to this booklet. 



Whilst the notorious house-frequenting flies above- 

 mentioned and the blue-bottle are remarkably omni- 

 vorous in their feeding, the great majority of outdoor 

 flies are quite otherwise inclined, and do not find much 

 attraction in anything but their own individual pre- 

 ferences. Indeed, the breeze-flies, and many others, 

 avoid human habitations ; even the grey blow-fly, unlike 

 the blue-bottle, rather seems shy of the house. In the 

 above grouping, according to feeding habits, the house- 

 fly must be preferably consorted with (2) sweat-flies, 

 but the blue-bottle with (6) carrion flies ; however, 

 the house-fly and the blue-bottle are very near akin, 

 and by reason of similarity of wing-pattern both 

 are included in the family of the Muscidce. 



