Nov., 1911.] 
Life- Hi stories of Syrphidae II. 
397 
LIFE-HISTORIES OF SYRPHIDAE II. 
C. L. Metcalf. 
Paragus bicolor (Fabricius). 
Larva. 
Length about 8 mm., height about 2.5 mm., width 3.25 mm. 
(Fig. 21). In superficial appearance somewhat suggesting larva 
of Didea fasciata fuscipes* 
Elongate-oval in outline, somewhat flattened-dorso-ventrally, 
attenuated gradually to the obtusely pointed anterior end slightly 
to the truncate posterior end. The color of the integument is 
light yellowish brown, but it is semi-transparent and various 
tints of visceral organs show through, making a light line along 
each lateral carina limited medially by darker. The mid-dorsal 
region surrounding the black pulsating blood-vessel is a light 
brick-red color about one-third the width of the larva, due to 
underlying fatty bodies. On each side of this for a third the 
remaining width jet-black visceral matter shows through fre- 
quently in pulsating pockets. This is limited laterally by a 
little wider band of yellowish white as contrasted with the narrow 
remaining margin and the conical elevations which appear drab. 
However, the color varies considerably with different larvae and 
at different times in the same larva. 
The integument is tough but pliable thrown into numerous 
transverse folds; papillose but bare. 
There are apparently twelve body-segments the anterior three 
strongly retractile so that when the larva is at rest segment four 
usually forms the anterior outline of the body. Each of these 
segments except the first few and the last is marked by about 
four lateral wrinkles or folds and bears, as in Didea, twelve conical 
elevations each with a spine or bristle at the summit. (Fig. 22). 
For convenience of reference we may name these segmental 
spines and the elevations on which they are borne according to 
their position. Beginning at the mid-dorsal line on either side 
they are in order: median, dorsal, dorso-lateral, lateral and two 
ventro-laterals, a posterior ventro-lateral and an anterior ventro- 
lateral, as one is in front of the other. This will be made clear by 
refrering to Figures 27 and 28 where these spines are indicated on 
the puparium. The fourth and fifth body-segments in Paragus 
bicolor have the median, dorsal, dorso-lateral and lateral eleva- 
tions of about equal size (see Fig. 21). The third and the sixth 
to the eleventh segments, inclusive, have the dorsal ones very 
much shorter, about one-sixth as large, almost obscure, and sit- 
uated on the succeeding fold of the integument. The dorso- 
*The Ohio Naturalist, Vol. XI, No. 7, pp. 337-344, 2 plates, May, 1911. 
