No. 64] DTPTERA OF CONNECTICUT: MORPIIOLCGY 97 



nite of the eighth segment 8s is large, and tlie parts of the ninth seg- 

 ment project directly backward. As we pass to the rhagionid (lep- 

 tid) type shown in Fig. 12, A, it may be noted that the eighth ster- 

 nite Ss is much larger than its tergite 8^, and the intersegmental 

 membranes become larger and more extensive to permit a greater 

 displacement of the parts in mating, and the ninth segment is able 

 to project iipAvard in this insect. The genital forceps cxi and st are 

 still clearly recognizable as such, but they tend to unite basally with 

 an area which may possibly represent the remains of the ninth ster- 

 nite, although this has not been definitely determined. 



In a somewhat higher stage represented by the stratiomyid 

 Ptecticus, shown in Fig. 12, C, the tergites of the seventh and eighth 

 segments 7t and 8t become reduced to snuiU transverse bands, and the 

 eighth sternite 8,s is apparently capable of at least a temporary dis- 

 placement into the insect's left side during mating; and the ninth 

 segment is capable of projecting dorsally. The ninth tergite 9t 

 bears a pair of processes ss which may represent the surstyli of the 

 higher Diptera. The distal segments or distimeres st of the genital 

 forceps are broad and fiat in Ptecticus (Fig. 12, C) like the api)arent 

 distal segments or distimeres -s;^ of the syrphid cyciorrhaphan shown in 

 Fig. 14:, H, and the basal segments or basimeres cxi of the genital 

 forceps of Ptecticus (Fig. 12, C) unite with the apparent ninth ster- 

 nite ds as the apparent basal segments or basimeres cxi do in the 

 syrphid shown in Fig. 14, H. The surstyli ss become articulated to 

 the ninth tergite 9;^ in the syrphid shown in Fig. 14, H. 



An advance in the direction of the development of the cyclor- 

 i-haphan type of postabdomen is illustrated by the dolichopodid 

 shown in Fig. 12, B^ in which the ninth segment has undergone a 

 partial "circumversion" (or "strophe"), resulting in the dragging up 

 of the eighth sternite Ss into the insect's left side, although the eighth 

 sternite has not become inverted as it does in many Cyclorrhapha. 

 The seventh segment is somewhat distorted in this dolichopodid and 

 its attachment to the sixth segment indicates that it has been afi'ected 

 by the torsion process. The cerci ce are rather suggestive of those 

 of the higher Cyclorrhapha, and structures suggestive of the surstyli 

 ss are developed in this dolichopodid, Avhose aedeagus ae projects down- 

 ward and forward in the cyclorrhaphan manner. The fifth sternite 

 5s is likewise cleft posteriorly suggesting the condition occurring in 

 the higher Cyclorrhapha in which the fifth sternite bears copulatory 

 lobes (Fig. 13, E). This dolichopodid thus foreshadows many of the 

 modifications occurring in the higher Cyclorrhapha, although it is 

 not directly ancestral to any of them. 



Apparently a pipunculid-syrphid-pyrgotid series may develop 

 in the Cyclorrhapha, since the modifications exhibited by the insects 

 shown in Fig. 12, E and I, are somewhat similar, and the torsion 

 inversion of the ninth segment is of the same type in both insects, 

 but the resemblances are not very close. The character of the nar- 

 row, transverse sclerite here interpreted as the vestigial seventh 

 tergite 7t, which bears the supposed seventh spiracle, and extends 



