1921] Metcalf: Genitalia of Male Syrphide 195 
(b). THe Cuitinous Box: There is often near the apex of the 
penis, standing mediad, a more or less globose or pyriform or variously 
shaped expansion called by Berlese the chitinous box (Figs. 27, Plate 
Ki 498 a0) goa, 93, Plate XT: 62; 67, 68, Plate XV; 76, Plate XIV; 
Ole Plate Sev 97, 100, 129, 1380; Plate X1X; 102, 105, a, 127, Plate 
XVII; 112, 118, d, 119, Plate XVIII). This is variously supported as 
described for the different species, but typically rests on the apex of the 
sustentacular apodeme (vide infra). The ejaculatory duct may pass 
through such a chitinized body before its termination and the orifice 
of the duct, when sessile, is usually toward the apex on its cephalic 
face. When an ejaculatory process is present it is an outgrowth of the 
chitinous box either from its cephalic face (Figs. 38, 40, 41, Plate X; 
45, Plate XIII; 119, 120, Plate XVIII), from its apex (Figs. 1, 60, 
Plate XV; 27, 28, Plate XII), or as in Syrphus and the related genera 
(Figs. 49, 50, 54, Plate XIII; 67, 68, Plate XV) the box is collar-like, 
widely open distad, and the ejaculatory process arises from within the 
box towards its caudal side. When the ejaculatory process is greatly 
elongated, the chitinous box is often displaced well toward the base of 
the penis sheath (e. g., Microdon, Ceriodes and Mixogaster, Figs. 129 to 
133, Plate XIX). 
(c). Tue Eyacutatory Hoop: Besides the ejaculatory aperture 
and process the chitinous box often bears a median structure on the 
caudal side, that, from its more typical shape, has been called the 
ejaculatory hood. It overhangs the aperture of the duct when it is 
sessile or on a short process (Figs. 2, 3, Plate XV; 5, 6, 9, 10, 11, Plate 
K-18, 48, 19, D1, 23, 25, Plate XI; 27,30, 32, 35, Plate X11; 40, 41, 
47, 48, Plate X-: 45, 46, 51, ¢, Plate XIN; 74, 75, 76,.c, 77, ¢; 81, 82, 
Plate XIV; 89, Plate XVI; 102, 103, 105, 106, 107, Plate XVII; 111, 
112, 118, 114, 115, 119, 120, Platé XVIII; 97, 131, 132, 133,.134, Plate 
XIX) or, if the process is very long, it may support and protect the 
apical part of it as in Chrysogaster spp. (Figs. 38, 39, Plate X) in Xylota 
spp., and in Mallota posticata. 
In other cases it is difficult to decide whether to consider the elabora- 
tions of the chitinous box an ejaculatory hood (Syrphus, Sphaerophoria) 
or internal lobes (vide infra) or simply a part of the chitinous box. 
The ejaculatory hood may be entirely wanting as in X ylota spp., Chilosia, 
and Microdon. When present it almost always affords a_ specific 
character. In some cases it helps to define a genus as in Paragus, 
Cnemodon, Calliprobola, X ylota, Criorhina, etc. Or it may serve to show 
something of the relationships of certain genera as in the Xylota, 
Cynorhina and Criorhina groups, which show a rather characteristic 
cordate hood in many of their species, (Figs. 105 to 107, Plate XVII; 
111 and 115, Plate XVIII). 
A few of the more remarkable developments of the ejaculatory 
hood are in Chrysogaster pulchella where, with the ejaculatory process, it 
resembles one of a pair of tongs (Figs. 36, 37, Plate X). In Chrysogaster 
generally it is much elaborated, often simulating a bird’s head, (Figs. 38, 
41, 48, Plate X). In Teuchocnemus (Figs. 96 and 100, Plate XIX) it 
is a long V-shaped affair, and in X ylota fraudulosa and Mallota posticata 
