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 run the full length of the tube are easily seen 
through the outer walls of this segment (Fig. 133, a). 
The tube terminates 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. (Buekton 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 swimming 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 flabellae about the 
anus, and the peculiar opening out and introverting of the anterior 
segments, lips, antennae, 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 form 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 strong!}’ convex in front 
and behind, weakly so along the middle. The ventral line is 
