June, 1922 bionomics of alphelinus semiflavus 215 



In spite of the fact that live parasites were confined with 

 these aphids for over a month during a period of rather mod- 

 erate weather conditions, none of them showed the character- 

 istic blackened appearance of parasitism. 



On May 5th, fifteen aphids were dissected and one parasite 

 egg found, w^hich appeared just ready to hatch. Later observa- 

 tions, however, showed no sign of parasitism. On May 20th, 

 more aphids were dissected in which were found three or four 

 well grown larvae, apparently normal. On the twenty-second, 

 one aphid had turned black. This was the only one of the lot 

 turning by May 24th when the experiment was closed. 



While the above observations are rough and incomplete, 

 they more than suggest a considerable influence of weather con- 

 ditions on the activity and development of Aphelinus. 



Where conditions are favorable, Aphelinus will multiply 

 throughout the year; the generations following each other in 

 cycles of 20 to 30 days, depending largely on temperature. 



BIONOMICS OF ADULT. 



Emergence. 



Emergence takes place through an irregular rounded hole 

 cut on the posterior-dorsal side of the blackened host remains. 

 The fact that the emergence hole is always cut in this one par- 

 ticular spot, is due to the peculiar orientation of the parasite 

 in respect to the host; the main axes of the latter being exactly 

 vice versa to those of the former, which always bring the 

 mouthparts of the parasite in this one position. 



Locomotion. 



Movement is rather sluggish in Aphelinus compared with 

 other aphid parasites. Unless disturbed, it usually crawls delib- 

 erately about among the aphids. At times, however, it was 

 observed to hop from one leaf to another, or from the side of 

 the cage over onto a plant. When stimulated with a needle, it 

 will hop away much like a flea; taking short jumps of two or 

 three inches. Many attempts were made to goad it into sus- 

 tained flight, but all were unsuccessful. In every case, it would 

 slant downward, even when held several feet above a piece of 

 white paper before a window. The wings are slightly reduced, 



