SARCOPHAGA AND ALLIES 13 



identified local collections of Sarcophagidse in the 

 United States, and dozens of workers who are compe- 

 tent to identify material and describe new species. 



Since the genitalia have this supreme importance 

 for taxonomy in this group, it is necessary to describe 

 their structure before passing to the analytical tables. 



The abdomen in Sarcophaga has four main seg- 

 ments, beyond which in males are two smaller seg- 

 ments of different appearance, called the hypopyg- 

 ium, or genital segments; the first of these may be 

 somewhat retracted into the fourth segment. The 

 anus is located at the end of the second hypopygial 

 segment. On the two sides, of the anus or just below 

 it are attached the forceps, two well chitinized organs 

 lying side by side and usually curving somewhat for- 

 ward below; they are generally visible in large part 

 without special preparation. They do not have lat- 

 eral motion, hence are not like true forceps. Their 

 shape is highly characteristic for each sj^ecies, and in 

 many of them is very striking (compare figures No. 

 21, 24, 36, 45, 68, 75). They are the hindmost of the 

 series of organs to be described. Assuming now that 

 the genitalia have been spread (a process to be de- 

 scribed a little farther on), the next important part 

 is the accessory plate, a more or less triangular sclerite 

 lying just in front of the outer side of the forceps 

 where the free part joins the segment. It offers 

 fewer characters than the forceps, but is often pe- 

 culiarly modified. The typical form is shown in fig- 

 ures 21, 22 and 23; in Fig. 26 it is developed into a 

 fingerlike process, and in 27 it is long and large, with 

 hooks on the posterior side ; compare also 9 and 52. 



Next in front of the accessory plates, and lying 

 nearer the median line, we come to two hooklike or- 

 gans, the posterior and anterior claspers, well shown 

 in figure 23. Each of these occurs in various forms, 

 long and short, straight and curved, as an inspection 

 of the figures will show. 



The forceps, accessory plates and claspers are all 

 paired organs, but the remaining one is unpaired, — • 



