NO. 12 FLYING APPARATUS OF BLOW-FLY — RITTER 9 



pleural cleft ; extends to the stigma anteriiis and ventrally reaches 

 the mesosternum, with which, and with the paratrema of Lowne, 

 it is connected by a bridge. Towards the anns a cleft, the fissura 

 episternalis, separates the parapleurum from the episternum. A 

 row of bristles runs along this fissure. The entire parapleurum is 

 clothed with hair. 



The episternum (pi. 2, figs. 3, 4, e) is narrow and dorsally re- 

 duced to the processus pterales episterni (see Cf,). Ventrally it 

 reaches the mesosternum, analwards the epimerum. 



The epimerum (pi. 2, figs. 3, 4, ep) has an elongated, oval shape, 

 and is closely set with long hairs. 



The parepimerum (pi. 2, figs. 3, 4, pm) which Lowne calls the 

 costa, lies dorsally between the episternum and the epimerum, leans 

 upon the latter, and like the epimerum is covered with hair. 



The parepistcrnum (pi. 2, figs. 3, 4, pe) lies dorsally upon the 

 epimerum. I give it this name because it is closely connected with 

 the episternum. It is triangular and considerably thickened on one 

 side in the form of a pediculated bud. Here, as in the case of the 

 stroma of the processus pteralis thoracis, we may make an exception 

 to the rule that names implying form should not be used, and from 

 its uncommonly impressive and striking l)ud-like shape, call it the 

 calyx. 



The Mesosternum 



The mesosternum (pi. i, fig. 2; pi. 2, figs. 3, 4, es) consists of 

 two symmetrical halves, from each of which a process extends to 

 the anterior pair of stigmata. These halves are nearly quadrilateral 

 in shape and strongly curved. With the two metasternums they 

 form the principal part of the central portion of the thorax. They 

 unite in the median plane, bend inwards (upwards), and form, when 

 united, the mesosternal process (furca of the mesosternum, Lowne; 

 pi. I, fig. 2, ap; see also below under Endoskeleton). The " lateral 

 plate of the postscutellum " of Lowne should be mentioned in pass- 

 ing as it is connected with the wing through the squama. It is 

 approximately triangular, strongly convex, and separated from the 

 processus postalaris by the foramen postalare (supratympanic fis- 

 sure of Lowne). 



ENDOSKELETAL PARTS 



The endoskeletal parts that are here to be considered are the 

 prsescutal crest, the mesapodema, which is continued into the epister- 

 nal border, the mesapophysis and the so-called parapterum. 



