THE GENETICS OF HABROBRACON JUGLANDIS ASHMEAD 



males, different ratios have been considered in 

 the publications. At first, ratio of females 

 among total progeny was used, but this was soon 

 given up in favor of ratio of total diploids. 

 Ratio of males among diploids was also calcu- 

 lated. It was noted that these two ratios were 

 negatively correlated and that outcrossed fe- 

 males had higher fecundity than close-crossed. 

 The latter fact, checked later by egg counts, 

 showed that low viability of diploid males, to- 

 gether with presence or absence of male-produc- 

 ing zygotes rather than difference in ratios of 

 eggs fertilized, lies at the basis of the nega- 

 tive correlation. Since, according to the mul- 

 tiple allele theory, male-producing zygotes are 

 formed in close-crosses with frequency equal to 

 female-producing, the ratio of diploid males to 

 females may be used to express the relative 

 viability of the diploid males. 



Bostian (1939) gave the first evidence sup- 

 porting the multiple sex allele theory. He se- 

 lected for independent segregation of fused and 

 sex for twenty generations, while constantly 

 inbreeding. He was unable to establish a line 

 breeding true for independent segregation of 

 sex and fused, although on the basis of Snell's 

 hypothesis, the establishment of homozygous sex 

 factors on the chromosome bearing fused would 

 allow for such a condition. The results of this 

 work indicate that there were triple sex alleles 

 present. A review by P. W. Whiting (1940c) of 

 the available data further supports and con- 

 firms the multiple allele theory of sex deter- 

 mination . 



The multiple allele theory of sex determina- 

 tion in Habrobracon has been exhaustively tested 



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