198 Annals Entomological Society of America  [Vol. XIV, 
(f). Tue EjacuLtatory Sac is an expansion of the efferent 
ejaculatory duct at its proximal end. It often takes the form of a 
bottle or flask and in almost every case has attached to it at its proximal 
end (the bottom of the flask) a chitinous rod or sclerite which may be 
called the ejaculatory apodeme. 
(g). THe EJACULATORY APODEME is often a complicated mechanism 
and it presents interesting variations that will well reward a complete 
exposition by some careful investigator. The typical condition of this 
sclerite appears to be an umbrella or toad-stool shaped piece which 
attaches to the bottom of the flask-like ejaculatory sac by the end of its 
handle (base of its stipe) while from the circumference of the base of the 
flask to the margin of the umbrella or pileus extend numerous delicate 
muscle fibers. The contraction of these fibers forces the piston-like 
part of the apodeme (the handle of the umbrella or the stipe of the toad- 
stool, as one pleases to think of it) into the bottom of the sac, collapsing 
the latter and expelling its contents with force. Such an umbrella-like 
arrangement is found in species of the following genera: Paragus 
(Fig. 11, Plate X), Chrysogaster (Figs. 36, 37, 41, 47, Plate X), Calli- 
proobola, Xylota, Spilomyia, Pterallastes, Brachypalpus and Temnostoma. 
A somewhat similar mechanism, but with the basal expansion of 
the apodeme small and knob-like or globular instead of umbrella-like, is 
found in Sphegina (Figs. 75, 76, Plate XIV), Sericomyia, Hammer- 
schmidtia, Brachyopa. Condidea lata shows a rather larger basal 
expansion intermediate between the above and the umbrella-like form. 
In Tropidia and Xylota spp., one finds a very gradual and slight enlarge- 
ment basad. A small curved rod with moderate distal expansion either 
gradual or abrupt, occurs in Platychirus spp., Melanostoma spp., 
Chrysotoxum, Syrphus, Xanthogramma, Blera, Baccha. In Blera scitula 
the rod is unusually long. A small curved rod without either a basal or 
distal expansion occurs in some species of Pipiza, Chilosia, Mesogramma, 
Psilota buccata (Fig. 33, Plate XII), Helophilus spp., Cynorhina. 
In Helophilus spp., Microdon spp., Eumerus strigatus and Somula 
decora there is a large sub-triangular, flat sclerite with the apex adjoining 
the ejaculatory sac. In Temnostoma, Ceriodes and Microdon it is very 
large, with a short cylindrical handle and a broad, flat, somewhat fan- 
shaped basal blade. In Mivxogaster breviventris it is similar with a 
longer handle and a spade-like blade with sharp shoulders and sides 
flaring out to a greater width at the base than next the handle. 
In Syritta pipiens I find a flat, broom-like sclerite not unlike that in 
some of the species mentioned above; but at the point where the 
cylindrical ‘“‘handle”’ terminates is a transverse piece composed of a 
median rounded expansion and two wings, the whole very similar in 
appearance to the head of a thumb screw. 
The most elaborately developed ejaculatory apparatus yet noted 
is that in Didea fasciata fuscipes. The apodeme is broom- or spade-like, 
with a handle not a fourth as long as the expanded part, the latter with 
rounded shoulders, parallel sides and broader than long; its area nearly 
as great as that of the tenth tergite. The ejaculatory sac appears to 
