XO. 12 FLYING APPARATUS OF BLOW-FLY RITTER 5 



liquor potassae it could, of course, be cut easily enough, but then it 

 showed deformations. The results of serial sections were satis- 

 factory only in studying the larger muscles (pi. 4A. fig. 10). 



Cross-sections of the wings imbedded in celloidin were easily pre- 

 pared and gave excellent results (pi. 4B, figs. 12, 13. 14). 



The stereoscopic pictures which illustrate this paper were photo- 

 graphed with a Zeiss binocular on color plates (Weslendorp and 

 Wehner). The contour drawings, with their lettering were pro- 

 duced as follows: The original stereoscopic photographs were 

 enlarged by means of an episcope, projected upon transfer paper 

 and copied thereon. These copies were then mounted on card- 

 board, provided with the lettering, and then again photographed and 

 reduced to the size of the original stereoscopic photographs. 



2. Gener^\.l Remarks Upon the Thoracic Skeleton of 

 THE Diptera 



Apart from the much debated microthorax, the thorax of insects 

 consists of three segments: the pro-, meso-, and metathorax. These 

 three segments are developed very unequally. In insects capable of 

 vigorous flight the segment or segments bearing the wings are better 

 developed than the others. In the Diptera the mesothorax, v^rhich 

 bears the single pair of wings, is developed much better than the 

 other two. The prothorax is greatly reduced. In each segment 

 there is to be distinguished : the notum or dorsal portion, usually 

 composed of the three parts, prsescutum, scutum, and scutellum ; 

 the pleura; or lateral portions, usually composed of the two parts, 

 episternum and epimerum ; and the sternum or ventral portion. 



Kolbe (1893) named the endoskeletal processes which extend 

 inward from the notumi, the pleura and the sternum: phragmas. 

 apodemse and apophyses, respectively. By prefixing the syllables 

 pro-, meso-, or meta- he designated the segment to which each 

 belongs. 



In Calliphora vomitoria the mesothorax forms by far the greatest 

 part of the whole thorax. The entire back of the thorax is covered 

 by the uncommonly well-developed mesonotum. 



I should like here to make some remarks concerning the deter- 

 mination of the limits between the thoracic segments. Kunckel 

 d'Herculais (1875) expressed the view that the mesonotum con- 

 sists of praescutum, scutum, scutellum and postscutellum. The deep 

 notches between the parts he considers as praescutum and scutum, 

 and the parts he considers as scutum and scutellum render it not 



