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-Hke 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 antennee, 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. 13s, 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. 



