Patterson: Polyembryony and Sex 



347 



males, but in five of the cases (Broods 

 3, 4, 5, 7, 8) this difference is not so 

 great but that the origin of each lot 

 can be explained on the assumption that 

 two parasitic eggs have been deposited 

 in the egg of the host. In each of the 

 four remaining broods (2, 6, 9, 10) fe- 

 males are greatly in excess of males, so 

 much so that it is difficult to explain 

 the origin of such broods on the basis 

 of two eggs. It was this evidence, al- 

 though meager in amount, that sug- 

 gested the possibility that such mixed 

 broods might be monozygotic, that is, 

 the origin of males and females from 

 a single fertilized egg. 



SEX RATIOS IN PARACOPIDOSOMOPSIS 



Three hundred and sixty- four para- 

 sitized carcasses of the AutograpJira 

 moth have been collected from the field. 

 Many broods of parasites have been 

 reared from these in the laboratory. 

 The sexes of the individuals in 177 

 cases have been studied. The results 

 of these studies show that only 3 broods, 

 or 1.7%, are pure female broods; 20. 

 or 11.3%, are pure male broods; and 

 154, or 87%, are mixed. ' 



The three female broods contained 

 1,089, 1,306 and 1,859 individuals, re- 

 spectively. The male broods vary from 

 385 to 1,588 individuals, with an aver- 

 age of about 1,000. The mixed broods 

 vary from 545 to 2.028 individuals, with 

 an average of 1,246 per brood. 



Sixty mixed broods, in which the 

 sex of each individual was carefully 

 determined, are listed in Table II, ar- 

 ranged in the order of percentage of 

 males, from the highest to the lowest. 

 In Table III are listed fifty additional 

 broods, in which the percentage of males 

 is based on an examination of 500 in- 

 dividuals in each brood. Reference to 

 these tables will show that the per- 

 centage of males varies from 72.07 to 

 0.06, and further, that in over 58% 

 of the broods less than 10% of the 

 individuals in any given brood are 

 males, while in 35% of the brood there 

 is less than 3% of males. The most 

 striking feature of these data is the 

 fact that females are so frequently in 

 excess of males. The significance of 



this will be discussed in a later sec- 

 tion of the paper. 



SEX RATIOS IN PL AT YG ASTER RUBI 



I have reared 105 broods of Platy- 

 gastcr, 67 from the carcasses of Rhopa- 

 loniyia and 38 from those of JValsho- 

 inyia. These are listed in Tables IV 

 and V. The total number of individ- 

 uals is 1,616, or an average per brood 

 of over 15. The broods from Rhopa- 

 loinyia are distinctly larger than those 

 from ]Valshomyia, the former averag- 

 ing slightlv over 18. the latter onlv 10.5. 



