188 



over the tipper surface of the leaves of the common milkweed, Ascle- 

 pias svriaca, and is so nimble that it requires a little care to catch it. A 

 large number of the flies were secured from the common milkweed 

 along the railway track (Sta. I) Aug. 12 (No. 27), and also on the 

 milkweeds infested with the plant-louse Aphis asclepiadis Fitch. Al- 

 though some species of DolicJwpodidcv are said to be predaceous, I 

 have never seen this species attack any insect. 



The peculiar breeding habits of some of the members of this fam- 

 ilv have been described bv Aldrich (Am. Nat., Vol. 28, p. 35-37. 



1894). 



Syrphid^ 



Syr pints aincricamis Wied. (PI. XLVII, figs. 3, 4, and 5.) 



This fly was taken along the railway track (Sta. I) Aug. 9 (No. 

 11). Its hum when on wing sounded much like that of the small yel- 

 low-jacket, Vespa. Metcalf ('13, p. 55) found it feeding on aphids 

 infesting Phragmites. 



Certain syrphid larvae prey upon plant-lice, and the adults are 

 abundant on flowers, especially unbellifers, feeding on their nectar. For 

 good accounts of both larvae and adults consult Williston (Bull. 31, 

 U. S. Nat. Mus., pp. 269-272. 1886) and Metcalf ('13). 



Mesograiniua polituin Say. Corn Syrphid. (PI. XLVII, figs, i and 2.) 

 This syrphid was found in great numbers on the Loxa prairie ( Sta. 

 II) Aug. 27 (No. 177). 



The larvae are pollen feeders, as has been shown by an examination 

 of the contents of the alimentary canal (cf. Riley and Howard, Insect 

 Life, Vol. I, p. 6). Also consult Forbes ('05, p. 162), who figures the 

 species. Upon the original prairie the species probably fed on the pol- 

 len of various grasses or other plants. 



Allogmpta obliqua Say. (PI. XLVII, figs. 6 and 7.) 



This insect was taken on the Loxa prairie (Sta. II) in company 

 with great numbers of Mesogramma politum Say, Aug. 27 (No. 177). 

 For figures of the larva, pupa, and adult see Washburn (Tenth Ann. 

 Rep. State Ent. Minn., p. 10 1. 1905) and Metcalf ('13, p. 58). It 

 feeds upon aphids. 



CONOPID^ 



Physocephala sagittaria Say. 



This insect was taken on the flowers of goldenrod, SoUdago (Sta. 

 I), Aug. 12 (No. 26). Also taken on a small-flowered aster at L'r- 

 bana. 111., Oct. 8. The larvae of this family are parasitic on other 

 insects. There is a figure of an allied species on Plate XLVIII, fig- 

 ure I. 



