30 MEDICAL ENTOMOLOGY 



teeth on the mandible cannot be distinguished at all. At the base the 

 blade is broader and stouter, and turns sharply outwards at its articu- 

 lation with the head ; the muscles attached to it are small, and the 

 mandible does not appear to play an important part in the cutting 

 operation. Mandibles are absent in the male, and the whole appendage 

 may be regarded as a retrogressing one. 



The maxillae (figs. 1 and 2), slender though they are, are stouter than 

 the mandibles. On section the two blades are seen to form a concavity 

 on which the hypopharynx rests. When mounted flat the blade 

 is seen to have one edge thick and rounded, and the other extremely 

 sharp and attenuated ; the surface between the two edges is divided into 

 a number of separate areas by means of transverse lines, which produce 

 slight indentations where they meet the thinner edge. At the distal 

 end there is a single row of short conical teeth, arising from the thin edge. 

 The number of these differs in different species, but is usually from ten 

 to twenty. At the base the blade merges into the stipes, which has often 

 been described as the ' apodeme ' of the maxilla. The retractor muscles 

 attached to it are much more powerful than the protractors. The palps, 

 which vary in length and in the number of joints in the different genera, 

 and are of importance in classification, are attached to the base of 

 the blade where it merges with the stipes ; as in the other forms, they are 

 held out in front, away from the proboscis, when the mosquito is feeding. 



In some of the larger mosquitoes the blade has a much more formidable 

 cutting apparatus than the one just described. In a species of Joblotia 

 (fig. 7) there are three sets of teeth. One set resembles that seen in 

 Anopheles, and does not extend quite to the tip of the blade ; these teeth 

 are only slightly recurved, and can probably cut in both directions, though 

 most efficiently in retraction. Distal to them and on the same border 

 there is a row of much finer and sharper teeth, which point towards the 

 tip, while at the extreme end of the blade, distal to the others, there is a 

 row of stout but minute teeth like those on the maxilla of Tabanus, ex- 

 tending on to both surfaces of the blade. Such a weapon will cut both 

 in protraction and in retraction. 



The labrum-epipharynx is not flattened as in the other forms, but 

 rounded. The constituent parts are more closely fused together, and 

 there is very little loose tissue between them. The epipharynx takes the 

 greater part in the formation of the stylet, and is produced beyond the 

 labrum. The distal end( Plate VI, fig. 3) is in most genera obliquely 

 truncated in such a manner as to resemble a J pen, and is incised in the 

 longitudinal direction, the portions of the margin between the incisions 



