1941] 
Male Diptera 
89 
to identify the parts of the Syrphid shown in Fig. 17 with 
those of the lower Diptera, and it is then comparatively easy 
to identify the structures of the higher Diptera which cor- 
respond to the parts in this Syrphid. 
In the Muscid fly Hylemya shown in Fig. 20, the structures 
which occupy a position on each side of the base of the 
aedeagus, ae, comparable to the parts situated on each side 
of the base of the aedeagus, ae, of the Syrphid shown in 
Fig. 17, are the so-called anterior and posterior “gonapo- 
physes” (b and d) of Fig. 20, and unless these so-called 
“gonapophyses” are structers peculiar to the higher Cy- 
clorrhapha, having no relation to the structures of the 
lower Cyclorrhapha, it is possible that these structures la- 
belled b and d in the higher Cyclorrhapha shown in Figs. 
20, 21, etc., may represent the basimeres, b, and the disti- 
meres, d, of the primitive Cyclorrhaphan, Syrphus, shown 
in Fig. 17. 1 In the same way, the appendages, st, of the 
ninth tergite, 9t, and the lobes, ce, on each side of the anal 
opening of the higher Cyclorrhapha shown in Figs. 19, 
21, etc., may be identified with the surstyli, st, borne on the 
ninth tergite, 9t, and the cerci, ce, situated on each side of 
the anal opening, of the Syrphid shown in Fig. 17, and it is 
thus an easy matter to homologize the structures of the 
higher Cyclorrhapha by comparing them with the struc- 
tures of the key group Syrphidse. 
With regard to the minuter details of the genital struc- 
tures of the higher Diptera, it may be remarked that Lowne, 
1895, in the second volume of his monumental work on the 
blowfly Calliphora, designates the slender structure labelled 
p in Fig. 21 of Phormia regina as the paraphallus, and calls 
the structure labelled h in Fig. 21 the hypophallus. The 
genital spine labelled e in Figs. 19 and 21, etc., is usually 
called the epiphallus, and the basal and distal portions of 
aedeagus ae, labelled a and ph in Fig. 21 have been called 
the phallophore and phallus. 
Of the internal structures in this region, mention may be 
made of the phallic apodeme, pa, of Figs. 19 and 21, which 
1 It is preferable to refer to the structures labelled b and d in Figs. 
19, 20 and 21, of the higher Cyclorrhapha, simply as the anterior and 
posterior gonapophyses until their homologies have been definitely 
determined. 
