Nov., 1911.] Life- Histories of Syrphidac II. 397 



LIFE-HISTORIES OF SYRPHIDAE II. 



C. L. Metcalf. 



Paragus bicolor (Fabricius). 



Larva. 



Length about S mm., height about 2.5 mm., width 3.25 mm. 

 (Fig. 21). In superficial appearance somewhat suggesting larva 

 of Didea fasciato fuscipes.* 



Elongate-oval in outline, somewhat fiattened-dorso-ventrally, 

 attenuated gradually to the obtusely pointed anterior end slightly 

 to the truncate posterior end. The color of the integument is 

 light yello\\dsh 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-seginents 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 wrinldes 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, 191L 



