Mar., 1913.] 
Life-Histories of Syrphidae V. 
85 
retracted so as to be roughly truncate. At the posterior end the 
last segment tapers rather abruptly to the posterior respiratory 
appendage. This appendage (Fig. 131, d) is tube-like and very 
long. Its diameter near the body is usually about 0.5 mm. while 
at the end it is less than one-half this width. Its length varies 
extensively; it is seldom retracted to less than 5 mm. and may be 
elongated in exceptional instances to 100 mm. or nearly four 
inches. A more usual elongation is about 15 to 30 mm. The 
color of the larva is a dirty gray or brown. 
The body-wall is soft, flexible, more or less greasy or slimy to 
the touch, and translucent. The integument has a number of 
transverse folds which terminate laterally in a moderately dis¬ 
tinct lateral carina running the full length. These folds fall into 
a number of groups, between which the integument is smooth, 
each group consisting of about five transverse elevations or 
wrinkles. Near the middle of these groups of folds one can detect 
double, flexible hairs (Fig. 136, a), about twelve in number sit¬ 
uated in a transverse row. The lateral margins of the body also 
are constricted between these groups of folds. 
For these reasons I am convinced that these divisions of the 
body represent somites or body-segments. I suspect that the 
bifid, flexible hairs are homologous with the single, usually rigid, 
segmental hairs of the aphidiphagous forms which are similarly 
located with reference to segments. Determined in this way the 
body shows seven similar and perfect segments when in a retracted 
position. To these may apparently be added two posterior ones 
which bear the long respiratory tube and on which the anus opens 
ventrally. Immediately in front of these seven similar segments 
open the anterior respiratory cornua of the larva, which would 
represent a tenth segment. The remaining ones in front are 
indefinite, retractile, and bear the antennae, a mouth-hood, and, 
within the buccal cavity, certain chitinized mouth-parts. If, 
as in the case of the aphidiphagous species, we consider the 
anterior larval spiracles as representing the prothoracic segment 
and allow, as in that case, two segments for the head, then this 
segment becomes No. 3, the last one of the seven would be No. 10, 
and the ones bearing the anus and respiratory appendage would 
make twelve in all. 
The mouth-parts of the larva are located internal to a hood¬ 
like, striated, chitinous termination of the oesophageal framework. 
(Figs. 138, b; 139). They are peculiar structures which I have 
been unable to homologize with the parts in the aphidiphagous 
larvae, but which seem to me to represent these structures in a 
degenerate condition. They are represented in Plate -, 
Figs. 139, 140, 141, perhaps better than they can be described. 
Of the parts there figured only the hood reaches the surface or 
can be seen without dissection. 
