VI l] 



EXTERNAL ANATOMY 



53 



something like an ft ; the slit-like opening is placed ventrally. 

 At its distal extremity the labrum of the female narrows to 

 a sharp point, whilst in the male the tip is truncated. 



(v) The hypopharynx arises just above the base of the 

 labium and in the female is shaped " like a two-edged sword." 

 When applied to the labrum it closes the ventral slit and the 

 two structures together form a suctorial tube. In the male 

 the hypopharynx is frequently fused with the labium and is 



Sw, 



Fig. 27. Side view of the head of a female Anopheles maculipennis, X about 

 26, with the various mouth-parts separated, but in the relative position 

 in which they lie when enclosed in the groove of the labium. After 

 Nuttall and Shipley. 



a, antennss ; cl, clypeus ; cs, cephalic scales ; hp, hypopharynx ; It, 

 labium; Ixe, labrum + epipharynx; mn, mandibles ; mp, maxillary palps; 

 mx, first maxillae. 



never adapted for piercing. In both male and female the 

 thickened ventral part of the hypopharynx is traversed by the 

 median salivary groove, ending at the distal extremity. 



The relative position of the mouth-parts is well shewn in 

 the accompanying diagram (Fig. 27). 



The thorax is by far the largest of the three divisions of 

 the body, being some 12-15 times as large as the head, and 



