256 P. W. WHITING. 



The excess of males (90 : 72) in the progeny of females mated late 

 in life is probably due to the fact that they did not mate after 

 being set with a male until after they had laid a few eggs. 



Summarizing then we have sixty-one females set with males 

 that produced both males and females (683 : 918), nine that 

 produced only males (197) and thirty-six virgin females that 

 produced only males (1133). Not a single female has been pro- 

 duced from a virgin female. 



The conclusion might be drawn then that in Hadrobracon 

 brevicornis fertilized eggs produce females and unfertilized eggs 

 produce males. If this is comparable with conditions in the 

 honey-bee and the hornet, it must be supposed that the male is a 

 haplont; the female, a diplont. An alternative possibility would 

 be that males are diplonts, in which case they might be formed 

 either from unreduced eggs or from reduced eggs that have been 

 fertilized by male-determining spermatozoa. 



Cytological work is now in progress that confirms the theory 

 that the male is haplont. The first spermatocyte division is 

 abortive as in the honey-bee. Details will be published later. 



Other work in regard to sex-determination in the Braconidee 

 is that of F. M. Webster (1909) and S. J. Hunter (1909) on Lysiph- 

 lebus tritici, belonging to the subfamily Aphidiinse. The results 

 of these investigations have been reviewed and discussed by 

 A. F. Shull (1910). Both males and females were produced 

 from mated females. Virgin females usually produced males 

 but occasionally a few females. 



The work done at the United States Parasite Laboratory at 

 Melrose Highlands, Mass., indicates that males are usually 

 produced from virgin females of Braconids and Ichneumonids, 

 but Hemiteles, an Ichneumonid hyperparasite, produces females 

 parthenogenetically as well. 



LITERATURE CITED. 

 Hunter, S. J. 



'09 The Green Bug and Its Enemies. Bulletin of the University of Kansas, 



Vol. IX., No. 2, October. 

 Shull, A. Franklin 



'10 Do parthenogenetic eggs of Hymenoptera produce only males? American 



Naturalist, Vol. XLIV., No. 518, February. 

 Webster, F. M. 



'09 Investigations of Toxoptera graminum and its parasites. Annals of the 

 Entomological Society of America, June. 



