Mar., 1912.] Life- Histories of Syrphidae III. 485 



is evident; the puparium is not strongly elevated posteriorly, 

 being eonvexly depressed gradually from about the middle. From 

 in front the puparium appears nearly circular in outline, very 

 slightly flattened ventrally. 



The posterior breathing appendage (Fig. 55, a) is as in the larva 

 but entirely black, the segment inflated beneath it. The anterior 

 spiracles remain visible externally, antero-dorsal to the tip of the 

 mouth-parts, with parts of the tracheae leading from them visible 

 flattened against the inside of the puparium (Fig. 51, a). The 

 larval mouth parts also become flattened against the puparium on 

 their right or left side. (Fig. 51, b, c, d). At first the pupa 

 shrinks away from these parts but later as the adult head develops 

 fills up the space again. A fine of weakness develops in the 

 puparium i-unning from the apex of the mouth-parts dorsally 

 between segments 6 and 7. The expanse of the ventral part of 

 the face then forces off a circular operculum along this line for the 

 emergence of the adult. Posteriorly part of the large tracheal 

 trunks remain in connection with the spiracles. 



Color of the puparium, empty: pale brown, transparent; with 

 pupa enclosed: variable, darker brown, strongly tinted with 

 salmon. A day or two before emergence the prominent colors ol 

 the adult become plainly visible. 



Pupa. 



The coarctate pupa (Fig. 54) is covered with a delicate trans- 

 parent membrane {a) with pockets encasing the developing legs, 

 wings, etc. The changes visible externally are gradually produced 

 and give little indication of the radical internal histolysis and 

 histogenesis. 



At an early stage (Fig. 53) when the dorsal part of the abdomen 

 is simply a mass of fatty granules as in the larva with the 

 position of the dorsal blood vessel indicated and the head and 

 thorax irregular, angular masses; the legs, or the cases enclosing 

 them (Fig. 53, a, b, c) have already reached their full size; although 

 there is no vestiture developed on them and their outline and 

 segmentation are indefinite. The wing-pads, also, (</), are as 

 large as they will become before emergence but show no signs of 

 the venation which is proininent at a later stage. They are folded 

 ventrally about the sides of the body. 



The mouth-parts are visible as long, cylindrical, fleshy buds {e). 

 The eyes are not indicated externally except as irregular oval 

 areas about half the size of the adult eye antero-dorsal in position, 

 bounded by a slightly elevated ridge. 



A considerably later stage shows the abdomen still cylindrical 

 without color and with only a little vestiture, the segments faintly 

 indicated by constrictions, the fatty granules gone. The head is. 



