80 THE CANADIAN ENTOMOLOGIST. 



States but that it would breed interchangeably from Toxoptera 

 into other species of Aphids and in addition was reared from a 

 large number of common and widespread species of Apids. Tak- 

 ing thesg facts into consideration it is very easy to see, as the 

 authors rightly point out, "that it would be only in rare instances 

 and under peculiar conditions that a locality would be found 

 where Aphidius testaceipes would not be lurking, waiting for 

 favourable weather conditions and abundant supplies of its host 

 aphids to make its appearance in greater or less numbers." The 

 effectiveness of this parasite will be appreciated when it is realized 

 that a single female Aphidius may parasitize no less than 301 

 Toxop'.era. No wonder their natural control is, at times, so sweep- 

 ingly effective! Regarding the artificial distribution of the parasites, 

 these investigations naturally point to the "futility of attempting 

 materially to increase its numbers or efficiency by artificial intro- 

 duction into grain fields" and further, I would add, they point to 

 the necessity of making as careful studies as possible of the 

 parasites before adopting any extensive system of artificial dis- 

 tribution. The account of the remedial and preventive measures is 

 prefaced by the statement that with "an outbreak of this pest 

 fully established and the winged adults being carried by the wind 

 and scattered over the fields there to settle down and reproduce, 

 the difficulties in the way of control are quite insurmountable." 

 Bush-drag experiments, and spraying did not give satisfactory 

 results or were impracticable. Cultural methods of prevention 

 are the most important and the chief of these is the destruction 

 of volunteer grain. In this connection I would venture to 

 suggest, would it not be well to leave the volunteer growth as a 

 trap crop, then seed later or sow spring oats? In the north the 

 close grazing of waste lands is recommended ; this would result in 

 the destruction of a considerable proportion of the eggs laid on 

 the Blue grass {Poa pratensis) which appears to be the normal 

 host of the Green Bug in northern localities. 



Great credit is due to Mr. F. M. Webster and his very able 

 assistants, particularly Mr. Phillips, for the thorough character of 

 this investigation, the results of which will be of great assistance to 

 others working in the same field and confronted with similar 

 problems. C. Gordon Hewitt. 



