PARASITE, APHIDIUS TESTACEIPES. 



105 



ents, both parent and offspring being preserved, Mr. H. L. Viereck, 

 of this bureau, has been able to determine definitely for us the iden- 

 tity of this species and to clear up the obscurity heretofore surround- 

 ing it. He finds that it has been masquerading under 14 different 

 names, and it seems that it may now be allowed to assume its right- 

 ful designation. 



Mr. Viereck, after a careful study of all material at hand, has sup- 

 plied us with the above list of synonyms. His work on the revision 

 of the genera Aphidius, Lysiphlebus, and Diasretus will appear later 

 in some other publication. 



LIFE HISTORY. 



OVIPOSITION. 



Under favorable conditions the females begin ovipositing within a 

 few hours after issuing, whether a male is present or not. When 

 the female is placed in the presence of Toxoptera she will rush about 



Fig. 20. — Aphidius testaceipes ovipositing in the body of the spring grain-aphis. Enlarged. (From 



Webster.) 



in an excited manner and when her antennae come in contact with an 

 aphis she stops very quickly and thrusts her abdomen beneath her 

 thorax and head (see fig. 20), giving the aphis a quick stab — some- 

 times several if the first attempts were unsuccessful; she oftentimes 

 lifts the smaller plant-lice completely from the leaf, they are stabbed 

 so fiercely. The act of oviposition shown in the illustration is not 

 intended to convey the impression that the Aphidius always attacks 

 the grain aphis at this point, as it will stab it from any position; it 

 will oftentimes reach around the margin of a leaf and pierce an aphis 

 on the opposite side. After being stung the aphidids kick up the pos- 

 terior part of the abdomen as though in pain, and sometimes a tiny 

 drop of fluid will appear at the tip of the cornicles. At no stage do 

 the aphidids appear to be exempt from attack. The Aphidius readily 

 attacks the winged, but apparently prefers the wingless forms. 



If parasites are confined with plant-lice for quite a while they will 

 stab them repeatedly, though we have never reared more than one 

 individual from the body of an aphis. It is very probable that in 

 cases of this kind it is the survival of the fittest, the strongest Aphidius 

 larva devouring all of the others. The junior author and Mr. W. R. 



