THE CANADIAN ENTOMOLOGIST. 205 



THE LIFE-HISTORY OF APANTELES GLOMERATUS, L.* 



BY ROBERT MATHESON, CORNELL U.VIVERSITY, ITHACA, N. Y. 



During the past summer, while doing some work on the larva of the 

 cabbage butterfly (Pieris rapae), I was struck by the lack of information 

 regarding the life-history of one of its most important parasites, Apanteles 

 glomeratus, L. In none of the publications on Economic Entomology 

 could I find any definite information, and the text-books were equally as 

 unsatisfactory. 



Reaumur, in his Memoirs, Vol. 2, pp. 417- states that the females 

 of this parasite deposit their eggs, one at a time, laying in all about thirty 

 eggs in each larva. He further adds that they select the intersegmental 

 areas as the place of oviposition, particularly between the eighth and ninth 

 and ninth and tenth segments. W. T. Bree. in the Mag. of Nat. Hist, for 

 1832, pp. 105-109, states that he observed several females in the act of 

 oviposition, and his description corresponds closely with that given by 

 Reaumur. Both writers emphasize the fact of the fearlessness of the 

 parasite during oviposition, and that only one egg is deposited each time. 

 Evidently what Reaumur and Bree observed was the oviposition not of 

 the true Apanteles glomeratus, L., but of Pieroinalus puparuin, L. f 



Seurat, '99, in his " Contributions a I'etude des Hymenopteres Ento- 

 mophages," states that the females oi Apanteles glomeratus oviposit in the 

 young larvae, depositing a large number of eggs in each. 



In rearing a large number of these parasites I was able to observe the 

 act of oviposition as well as to trace their life-history. The adults, on 

 emerging, do not immediately fly away, but remain walking back and 



*Contribution from the Entomological Laboratory of Cornell University. 



1(1 had an excellent opportunity for observing' the manner of oviposition of 

 this latter parasite, and it corresponds exactly with that given by Reaumur and 

 'Qree ior Apanlilcs glomera/us. I found Ptcroiiialus pupantiii at work late one 

 afternoon. It was not at all disturbed by my removing the larva to a small box. 

 Taking them to the laboratory, I was able to observe the act of oviposition under 

 the microscope, without in the least disturbing the insect. I watched it oviposit 

 at intervals of about twenty minutes till nearly 11 p.m., and next morning I found 

 it still ovipositing. It ceased early in the forenoon, so that in all probability it 

 had laid over thirty eggs in the one larva. The conclusion, that both Reaumur and 

 Bree had observed the oviposition of this species rather than of Apanteles 

 glumeralits, is strengthened by the fact that Reaumur states that the larvse of 

 these parasites are sometimes found in the chrysalidsof Pieris rapse, but after the 

 fourth day exhaust the food supply, and do not transform. This is the condition 

 we would expect to find in the case of Pteromalus puparum during the latter pai't 

 of August and the first of September, as it passes the winter in the larval state, 

 and does not spin its cocoon till the following spring.) 



June. 1907 



