196 Annals Entomological Society of America  [Vol. XIV, 
it takes the form of a long, shallow trough that forms a beautifully- 
adapted support for the remarkable ejaculatory processes of those 
species. It is remarkably long in Ceriodes spp., and shows some very 
interesting specializations in Mesogramma. In this genus there is also 
sometimes a short, erect, subcylindrical process cephalad of the ejac- 
ulatory aperture that looks very much like an ejaculatory process 
and would be mistaken for such if one did not follow the ejaculatory 
duct, which does not open into it. 
(d). InreRNAL Lopes: For those appendages or projections of 
the chitinous box that neither immediately surround and support the 
ejaculatory duct, as the ejaculatory process does, nor stand in the 
median caudal position, as the ejaculatory hood does, I have used the 
term internal lobes. ‘These are lateral in position, are paired and are 
claspers in function. They are at most of two pairs, respectively 
caudal and cephalic in point of attachment to the apex of the chitinous 
box. Such lobes are developed in Pipiza (Fig. 35, Plate XII), in which 
they are a pair of erect, narrow plates prolonged into acute points; in 
Mesogramma (Figs. 45, 46, Plate XIII). In Sphegina lobata (Fig. 70, e, 
Plate XIV), they are flattened plates; in an unnamed species of 
Sphegina they are remarkably developed and remarkably unsymmetri- 
cal cornua as shown in Figure 72, Plate XIV; in S. petiolata (Figs. 74 
and 75, Plate XIV) and S. rufizentris (Figs. 76 and 77) they are 
symmetrical and not greatly unlike those of Pipiza femoralis. In 
Baccha sp. they are large thin plates guarding the sides of the remark- 
able ejaculatory process. Other examples of the internal lobes are shown 
in Pterallastes and Teuchocnemis (Figs. 96, 97, 100, Plate XIX) in 
Xylota spp. (Fig. 106, Plate XVII), Chilosia spp., Sericomyia (Fig. 
109, Plate XVII), Criorhina spp. (Figs. 112, 113, Plate XVIII), Milesia 
(Fig. 119), Mallota posticata and Temnostoma (Figs. 123, 128, Plate 
XVII). 
Besides the external parts certain internal- structures have been 
considered. The gonads and their efferent ducts and accessory glands 
have not been studied; but the ejaculatory sac, the piston-like ejacu- 
latory apodeme often associated with it, the efferent ejaculatory duct, 
and the chitinous, reinforcing sustentacular apodeme, (which gives 
support to the penis, especially to the chitinous box at its apex, and to 
which muscles attach that serve to rotate and protrude the parts); 
these parts are generally evident in the cleared preparations, they often 
show characteristics of systematic value and consequently they have 
been described in connection with the external genitalia. 
(e). THE SUSTENTACULAR APODEME has been called by Wesche the 
double apodeme, and he states that it is often a paired organ in many 
families of the Diptera; in others partially fused; and again entirely 
united on the median line. In the Syrphidz it is typically a single rod, 
having its base in segment nine and projecting to a variable distance 
into the penis along or near the long axis. It does not articulate with 
the body wall of segment nine, nor with the penis sheath except rarely 
as in Sphegina rufiventris and petiolata; but is held in place by muscles, 
