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



terniod the basimeies or basistyles, and the distal seg-ments of the 

 genital forceps will be termed the distinieres or dististyles in the 

 following discussion of the modifications of the segments of the para- 

 meres in different male Diptera. 



The segments of the forcipate parameres are slender in male 

 Ciilicidae (Fig. 7, H, cxi and st), Ptychopteridae (Fig. 10, K, cwi and 

 st). certain Tipulidae (in which family the distinieres are usually 

 divided into an inner and outer portion labelled in and ot in Fig. 7, J), 

 Trichoceridae, Tanyderidae, and other primitive Nematocera, and the 

 basimeres tend to unite with the ninth sternite even in the lower 

 Nematocera. As we pass to the Bibionidae (Fig. 12, G), Leptidae 

 (Fig. 12, A) and other intermediate forms, the basimeres, cxi, become 

 shorter and stouter (and apparently unite with the ninth sternite) ; 

 and in the stratiomyid Ptectious, shown in Fig. 12, C, the distinieres 

 st become broad and flat, as they do in the syrphid Syrphus rectus 

 shown in Fig. 14, H (where the distinieres are labelled st), and the 

 reduced basimeres cxi of Ptecticiis (Fig. 12, C) unite with the ninth 

 sternite as the basimeres cxi do in Syrphus rectus (Fig. 14, H). The 

 so-called anterior and posterior gonapophyses ago and pgo of the 

 higher Cyclorrliapha such as Hyl&myia antiqua (Fig. 13, D) flanking, 

 the base of the aedeagus pha were formerl}'^ homologized with the 

 segments of the genital forceps of lower Diptera by the writer, but 

 this view is apparently incorrect, as will be discussed later on. 



The ninth abdominal tergite (a sternite according to Cole, 1927) 

 which apparently unites with the eighth tergite in the ptycliopterid 

 Bittacomorpha (Fig. 10, K) bears a pair of long slender processes, ss, 

 called surstyli in lower insects. These may correspond to the proc- 

 esses of the ninth tergite labelled ss in Fig. 12, C, of the stratiomyid 

 Ptectlcus, and these in turn may correspond to the articulated surstyli 

 ss borne on the ninth tergite of the Syrphidae (Fig. 12, F), which, 

 have been homologized with the surstyli or edita ss of the higher 

 Cyclorrhapha shown in Fig. 13, D, E and F, etc., in which these struc- 

 tures are greatly developecl to aid in mating (and are rather closely 

 associated with the cerci). 



The Post genital Structures of Male Diptera. The postgenital 

 segmental complex forming the so-called "anal segment" or proctiger 

 is small and inconspicuous in most male Diptera. It is closely 

 associated with the ninth tergite, by which it is concealed in most of 

 the lower Diptera, but in the higher Diptera (in which the cerci are 

 thrust downward and forward against the surstyli) the proctiger be- 

 comes more exposed to permit the free discharge of the faeces at all 

 times, even in copula. 



The proctiger or "anal segment*' is here regarded as composed 

 of the united tenth and the cercus-bearing eleventh segment (with 

 which the anus-bearing telson has fused), although Snodgrass (1935), 

 and most other investigators, refer to it as the tenth segment alone; 

 and Snodgrass refers to its appendages as the lobes of the tenth seg- 

 ment (socii'O, instead of cerci, since he considers that the cerci are 

 absent in the Diptera. Christophers (1923), however, in tracing the 



