88 GNATS OR MOSQUITOES — CHAPTER VI 



a portion of the prothorax projects in the form of a pair of 

 lateral protuberances, the shoulder callosities ; and on either 

 side of the scutellum, which appertains to the mesothorax, 

 can be seen, even in the extended insect, a portion of the 

 better-developed metathorax, v/hile in flexion the whole 

 width of its tergum can be easily seen. Laterally, how- 

 ever, the three component segments are easily distinguish- 

 able by the fact that each gives origin to a pair of legs, 

 the coxae of which guide the eye to the corresponding 



Fig. 20. — p, prothorax ; m, mesonotum ; h, metanotum ; k, scutellum 

 P2), propleura ; mp, lobes of metapleura ; 77itp>, metapleura ; s, s, s, thoracic 

 stigmata ; w, root of wing (after Arribiilzaga). 



portion of the thorax. Just in front of the root of the 

 coxa of the front leg can be seen, in the great majority of 

 species, an oblong or oval scale, which covers the stigma 

 of the prothorax. 



The stigma of the mesothorax is also well developed, 

 and can easily be seen just in front of the origin of the 

 wings ; but those of the metathorax, on the other hand, 

 are small or not recognisable. From the propleura springs 

 the coxa of the front leg, and between it and that of the 

 middle leg is a comparatively large area of mesopleura. 

 This latter is more or less divisible into three areas, one 

 of which carries the stigma, the second the middle leg, and 

 the third and hindmost the wings. From the metapleura 

 springs the coxa of the hind legs, and above it may be seen 



