Mar., 1913.] Life-Histories of Syrphidae V. 87 



marked by irregular longitudinal ridges bearing, in longitudinal 

 lines, very short, sharp, recurved hairs, broad at the base (Fig. 

 135). These alternate on any two adjoining ridges. The ter- 

 minal segment is smooth, shiny, with its surface transversely 

 ridged in a manner which, under low magnifications, suggests a 

 trachea. When more carefully examined, however, the two 

 trachea which ran the full length of the tube are easily seen 

 through the outer walls of this segment (Fig. 133, a). 



The tube temiinates in a rounded, convex tip which seems to 

 be perforated by two small semi-circular slits. It is ornamented 

 with four pairs of tiny, delicate, feather-like appendages which 

 open out radially. (Fig. 133, c). These are probably lubricated 

 in some way for they seem to repel the water and are not easily 

 submerged. These feather-like structures may be homologous 

 with the inter-spiracular hairs or spines of the aphidiphagous 

 larvae. 



These larvae can progress through the water by undulatory 

 constrictions of the body, or creep over submerged or exposed 

 objects by the aid of their pro-legs. (Buckton believed that in 

 E. tenax the tail is used by pushing from behind to aid the grub in 

 penetrating into soft mud.) 



Numerous larvae were collected in the evaporating vats at the 

 Columbus sewage disposal plant in September. They were found 

 in large numbers swiniming about in the very putrid, watery 

 material, near the surface where a kind of scum had collected. 

 Their food is undoubtedly the various decaying materials brought 

 in with the sewage. 



These are very interesting animals to watch under a low 

 power microscope: the peculiar undulatory creeping or swimming 

 movements, the retraction and elongation of the breathing 

 appendage, the occasional unfolding of the flabelte about the 

 anus, and the peculiar opening out and introverting of the anterior 

 segments, lips, antennee, mouth-hood, etc., besides the action of 

 the viscera all being clearly visible, and fascinating objects for 

 study. 



Pupa. 



While the change from larval- to pupal-stage in the aphid- 

 iphagous forms is not sharply defined, it is clearer there than in 

 the rat-tailed foim as illustrated by E. ceneas; because in the 

 latter case, the shortening and dorsal inflation are proportionately 

 not so great. 



Length 8-10 mm., height 3-4.5 mm., width 3. 5-4. 5 mm. 

 Shape elongate-ovoid, much like that of the larva but consider- 

 ably shortened, and somewhat inflated dorsally; so that as seen 

 from the side (Fig. 145) the dorsal line is strongly convex in front 

 and behind, weakly so along the middle. The ventral line is 



