48 ENTOMOLOGY FOR MEDICAL OFFICERS 



(4) SimuliidcB (p. 123). All the species (numbering more 

 than 100) of this family are extremely bloodthirsty, and the 

 females have mouth-parts of a most trenchant type (Fig. 30). 

 The family is represented in all parts of the world. 



These four families will be reviewed first. 



(a) Blood-sucking Nematocera. 



Family CULICID^E. 



The Culicidae can be distinguished from all other midge- 

 like flies by the venation (Fig. 7), and by the close fringe of 

 scales on the posterior border of the wings ; usually also 

 they have a projecting proboscis of extraordinary length. 



The head is small and subspherical, and there is a distinct 

 neck ; the crown and the cheeks are covered with scales 

 which show specific differences. The eyes are reniform, and 

 there are no ocelli. The antennae, which are long and 

 slender, are composed of 14, sometimes 15, segments, the first 

 being globose and broadly sessile on the head, while the 

 others are cylindrical, and carry — most of them — whorls of 

 hairs, which in the female are wispy, but in the male are, as a 

 rule, so thick-set as to give the antenna the look of a small 

 bottle-brush. The clypeus is prominent. The labium (pro- 

 boscis) in the majority of Culicidae is long and slender, is 

 covered with scales, and ends in a pair of small stiffish 

 labella ; it is not employed for piercing or sucking, but is 

 arched downwards during these operations, the labella then 

 being used as guides for the piercing organs. The maxillary 

 palps, which also are covered with scales, show specific and 

 sexual differences, being sometimes longer than the proboscis, 

 and sometimes very short. The parts ensheathed in the 

 proboscis also differ according to species and sex. In one 

 small subfamily {Corethrince) they are short, and are not 

 formed for piercing ; but in the females of all other Culicidae 

 they are long sharp piercing organs, and consist of the follow- 

 ing parts (Fig. 2) : — (i) a stoutish, pointed epipharynx, which 

 is grooved ventrally; (2) a slender hypopharynx, which — 

 itself an efferent tube for the saliva — is applied to the epi- 

 pharynx so as to convert the groove of the latter into an 

 afferent suctorial tube; (3) a pair of slender mandibles 



