154 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



FIGURE 9a. Posterior Abdominal Structures. 



A. Diagrammatic representation of the internal anatomy of the 

 genital system of a male metopiid (calliphorid) fly, based on Phomiia 

 regina^ showing the looping up of the vas deferens and ejaculatory 

 duct over the top of the rectum, before discharging through the phallo- 

 some or aedeagus. The gonapoph3'ses, etc., are slightly displaced for- 

 ward to show the base of the aedeagus. 



B. Lateral view of the postabdomen of a female syrphid, 

 Eristalis arhustarum^ showing the spiracle of the seventh abdominal 

 segment in its normal position. 



C. Diagrammatic figure of the postabdomen of a female an- 

 thomyid fly, FJammomyia paludis, showing the migration of the sev- 

 enth spiracle forward into the intersegmental membrane between the 

 sixth and seventh abdominal segments. 



D. Lateral view of the postabdomen of a female metopiid (cal- 

 liphorid) fly, Gynomya cadaveriTia, showing the displaced seventh 

 spiracle now borne in the sixth abdominal tergite, which also bears the 

 sixth spiracle as well. 



