FLIES FOUND IN HOUSES 9 



undergo semirotation, and carries the mouth parts, the visible 

 portions being the maxillary palps and the proboscis, through 

 which the fly sucks up the fluids on which it feeds. The upper 

 part and sides of the head are mainly occupied by the large 

 compound eyes. On the top of the head, in most of the flies with 

 which we are dealing, the eyes are close together in the males 

 and wider apart in the females, thus affording a ready means 

 of distinguishing the sexes. During life the eyes are frequently 

 of brilliant colours and variegate with stripes and spots ; this 

 condition disappears speedily after death, and it is uncertain 



Fig. I. Dorsal view. 



Fig. ^. Front view. 



Fig. 3. Side view of the head of the Flesh fly [Sarcophaga caniaria) ( x 6). The 

 actual sizes of the specimens are shown in the smaller figures. 



A, vertical bristles ; B, ocelli ; C, vertex ; D, frons, or front ; E, fronto-orbital 

 bristles ; F, antenna (third segment) ; G, arista ; H, face ; I, frontal lunule (con- 

 tinued downwards on each side external to the antennse to form a crescent-shaped 

 scar) ; J, compound eye ; K, cheek ; L, jowl ; M, maxillary palp ; N, proboscis ; 

 O, vibrissa. 



what the use of this colouration may be. In addition to the 

 compound e\'es many flies possess small simple eyes, or ocelli, 

 which are usuall\^ three in number and set in a triangle, apex 

 forwards, on the crown of the head. The antennce, which are 

 the principal means of classifying flies, are tactile and perhaps 

 olfactory organs, generally placed between the eyes. They vary 

 greatly in details of structure and may even differ in the sexes 

 of the same species. The space between the eyes above the 

 antenna is the front or frons ; that between the root of the 



