THE GENETICS OF HABROBRACON JUGLANDIS ASHMEAD 



ing up on each other as they would if the vial 

 v/ere kept upright. As they develop into mature 

 wasps, they can be observed through the vial by 

 means of a hand lens or a binocular dissecting 

 microscope, and as the sex becomes evident, the 

 males or any questionable pupae may be killed 

 with a needle, thereby insuring the eclosion of 

 virgin females only. 



If it is necessary to rear all the progeny 

 but still to retain the females as virgins, 

 another method is effective. This consists of 

 placing the caterpillars and wasp larvae on 

 cellophane discs placed in petri dishes. When 

 the larvae have pupated, the sex of the pupae 

 may be determined by viewing them from the un- 

 der side of the cellophane by means of a hand 

 lens or a microscope. The sexes may be sepa- 

 rated by cutting the cellophane surrounding 

 them, and the males and females may be placed 

 in separate vials to await eclosion. 



Various non-genetic influences affect the 

 ratio of offspring. Sperm supply in the semi- 

 jial receptacles influences the female ratio. 

 Production of females tends to be somewhat re- 

 duced in later culture vials preceding their 

 total absence after exhaustion of sperm supply. 

 Matings with old males result in lower female 

 ratios than matings v;ith young males, probably 

 l)ecause of lowered sperm supply. In much of 

 the earlier work, entire fraternities were sum- 

 marized including the haploid males produced 

 after depletion of sperm. Ratios thus obtained 

 are subject to great variation. They depend in 

 large measure on the length of life of the 

 mothers, who may die before they have exhausted 



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