54 THE CANADIAN ENTOMOLOGIST 



case of A. pomi the aphids were usually too much exposed to the direct ra> s of 

 the sun to afford the shelter required by syrphid larvae. On M. cerasi and -:4. 

 brassiccE it was exceedingly common and a very important check. About oO% 

 of the lar\^ae were parasitized during last year. 



Sphaerophoria cylindrica Say. An exceedingly common species, fciund 

 in abundance from early May to early November. The larva is a general feeder, 

 but prefers aphids found on low-growing plants. It and the larva of A. obliqua 

 are \ery similar, and without close examination are ordinarily considered as 

 the same species. They are found on the same plants as the preceding, and 

 the remarks on that species apply here also. 



Syrphus aniericanus Wiedemann. Is a well-known member of the 

 family. It is common in orchards and gardens, especially where plants are 

 infested with aphids. During 1919 the larva? were found feeing on Aphis 

 brassiccE, A. rnmicis, A. cardiii. A. pomi, A. gossypii, Macrosiphum sp. on wild 

 lettuce, and Myzus cerasi. 



The larva? are quite common on all the hosts mentioned above. It is of 

 considerable economic importance as a check of aphids attacking culti\ated 

 plants and fruits. 



Syrphus ribesii Linne. Larva found attacking: Aphis brass icce^ 

 A. cardui, A. pomi (apple and pear). A. gossypii, A. viburnicola, Myzus cerasi ^ 

 Eriosoma lanigera, Macrosiphum pisi, and Macrosiphum sp. on wild lettuce. 



Syrphus ribesii is probably the best known member of the family, and is 

 very common in orchards and gardens. Unfortunately this species and others 

 are frequently mistaken for bees, and are often killed in mistake for such. It. 

 is probably the most important species in the orchard, where it occurs in moder- 

 ately large numbers throughout the season from early May to November, 

 attacking especially Aphis ^nalifolice- and A. pomi, and to some extent, the 

 Woolly Aphis of the apple. It is the most common species attacking currant 

 aphids, and is usually very common during October on Viburnum, where the 

 larvae attack the return migrants and sexual females of Aphis viburnicola and 

 A. rumicis. 



The larvae are also found in large numbers in vegetable gardens on cab- 

 bages, etc., which are infested with aphids. They usually prefer well-shaded 

 places, such as curled leaves or dense foliage, but are often found in more exposed 

 positions. 



Syrphus torvus Zetterstedt. Is an extremely important species. Dur- 

 ing the first warm days in spring the adults emerge and eggs are laid on the 

 first colonies of aphids appearing on the shoots of various plants. The young 

 larvae develop on clusters of stem mothers and often wipe out whole colonies. 

 Again in the autumn it preys upon the return migrants and sexual females, in 

 addition to li\ing upon summer forms of aphids upon various plants. 



Paragus tibiaUs Fallen is rather common in Ontario. The larvae are 

 enemies of the pea aphis {Alacrosiphnm pisi), but I have observed them more 

 frequently attacking Aphis cardui on thistle. 



Paragus bicolor Fabricius is similar in habits to the preceding, but is 

 much less common. 



