BENEFICIAL INSECTS, PR:EDA('K01:S AND PAHASITIO. 35 



The adult syrplius-fi}^ is a very striking insect, with its 

 dark green metallic thorax, and abdomen variously banded 

 with yellow and black. The 

 female fly lays her eggs 

 upon some plant bearing 

 plant lice. The 1 a r v ae 

 which hatch from these are 

 elongate, flattened mag- 

 gots,about one -half an inch 



long, with hardlv a trace Fig U. — Syrphm rihesii. (Au- 



° -^ , thor's illustration. ) 



of a head, but with four 



small hooks, which serve as jaws, projecting from the more 



pointed end of the body. These maggots are often of a 



light green color, and so like the color of the plants as to 



render them most ditflcult to be recognized. The young 



larvae at once commence crawling over the plant in search 



of the aphids, and as soon as they come in contact with 



one it is firmly clasped by the small booklets until the 



juices are sucked from its body. In this manner very 



Fig. 15. — The Koot-loiise Syrphus-fly {Pipiza radicans). a, mag- 

 got; b, piiparium; r, fly. (After Riley.) 



large numbers are destroyed, a single maggot of tlie 

 American Syrphus-fly {Syrphus ainericanus) having been 

 observed to eat twenty-five Apple Plant-lice {AjjJiis mali) 



