14 



DIPTERA — MOUTH-PARTS 



[CH. 



however, possess antennae of a totally distinct form, peculiar 

 to the order, consisting of three segments, the outer one of 

 which, at its distal extremity, bears a fine process known as the 

 arista, which is occasionally segmented and often covered with 

 hairs. It probably represents the remaining segments of the 

 more primitive type of antennas. 



Fig. I. An Anthomyid fly immediately after emerging from the puparium, 

 shewing the greatly distended ptilinum and unexpanded wings. 



Figs. 2 and 3. Ventral and side views of the head of the same fly. After 

 Graham-Smith. 



The mouth-parts are composed typically of the following 

 structures : labrum, epipharynx, maxillae, mandibles, hypo- 

 pharynx and labium. These are liable to great variation, 

 even within the same family, but all blood-sucking Diptera 

 agree in the possession of a mouth that is adapted for piercing 

 and cutting. The labrum, or upper lip, together with the 

 epipharynx, is usually elongated ; the hypopharynx, or tongue, 

 is also much prolonged and, together with the labrum, may 

 form a tube for the ingestion of blood or other liquids ; the 



