SEX CONDITIONS 



gous sons. If biparental sons are produced 

 they maybe readily separated from their azygous 

 brothers by their black eyes. 



Fertilized eggs may be "female-producing" or 

 "male-producing," the latter occurring only if 

 parents are related. "Male-producing" ferti- 

 lized eggs are less likely to hatch than "fe- 

 male-producing." Consequently there are more 

 "bad eggs" and fewer biparental offspring if the 

 mating has been v;ith a related male, since the 

 percentage of eggs fertilized is the same wheth- 

 er the male is related or unrelated. Biparen- 

 tal male larvae are also less likely to mature 

 than female larvae. This further reduces off- 

 spring from related parents. 



Two types of male sterility may be distin- 

 guished in Habrobracon. If the eggs are not 

 fertilized, the mated female breeds like an un- 

 mated female, producing a large number of azy- 

 gous sons. This occurs in the case of matings>- 

 with biparental males which produce diploid 

 sperm rarely capable of fertilizing eggs. There* 

 are also males with abortive sperm ducts or 

 testes which may readily be mated but transmit 

 no sperm. Recent evidence indicates that sperm 

 may to some extent be inactivated by high dos- 

 ages of X-rays, so that they are unable to pen- 

 etrate the eggs. 



Cytological studies indicate that there are 

 ten chromosomes in the normal haploid male (Fig. 

 12) and twenty in the biparental diploid male 

 (Fig. 12). The normal female has twenty chro- 

 mosomes (Fig. 12), while the daughters of normal 

 mothers and biparental fathers have an as yet 

 undetermined but considerably larger number, in 

 all probability thirty. A spermatogonlal study 



77 



