THE GENETICS OF HABROBRACON JUGLANDIS ASHMEAD 



new factors. No consistent differences have 

 been found between F2 fraternities resulting 

 from reciprocal crosses (a female X b male and 

 b female X a male in the case of repulsion tests 

 or + female X a.b male and a.b female X + male 

 in the case of coupling tests). When two mu- 

 tant types are female sterile, the female het- 

 erozygous for one is crossed with the male of 

 the other, in which case only those F2 frater- 

 nities containing both mutants are of value. 



Unmated females resulting from crosses in- 

 volving various mutant genes produce males par- 

 thenogenetically . These segregate in gametic 

 ratios. Thus a female, o/bl , from a cross of 

 orange-eyed by black-bodied, shows independent 

 segregation of these two differences. The four 

 types of sons, wild-type, orange, black, and 

 orange-black, occur in equal numbers. The same 

 result is obtained from the reverse cross fe- 

 male, +/o.bl, resulting from a cross of wild- 

 type, by orange-black. Lemon body color and 

 cantaloup eyes are linked with about ten per 

 cent crossovers. Thus le/c females produce 

 males, +, le, c, le.c, in 1:9:9:1 ratio while 

 +/le.c females give the same types of male off- 

 spring in reverse ratio, 9:1:1:9. A female may 

 be heterozygous for several differences produc- 

 ing more complex ratios. Factor interaction is 

 shown, as in lemon, honey, and black, body col- 

 or, giving characteristic and clearly distinct 

 double mutant types, le.ho, le.bl, ho.bl, and 

 the triple mutant, le. ho.bl. Masking effects 

 are illustrated, as when white eyes prevent 

 other eye color differences from showing. Via- 

 bility differences appear when some mutant 

 types are less frequent than wild-type. Dif- 



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