GENE MUTATIONS 



presternum is much expanded so that the head is 

 thrust forward. When dead and dried, the mu- 

 tant type cannot be distinguished from normal. 

 Heterozygous females have fertility somewhat 

 reduced. Extended-head males have their via- 

 bility reduced somewhat less than fifty per 

 cent as compared with their v/ild-type sibs. 

 (Discarded) 



By far the most numerous mutations in Habro- 

 bracon, are those affecting the wings. Shape, 

 size, position, and venation may be affected 

 singly or in combination. The normal wild-type 

 wing is fairly regular in outline with a few 

 definite veins (Fig. 5). The v/ing mutations, 

 like all others, have been named from the ef- 

 fect most obvious to the discoverer. 



DEFECTIVE, d (veins). Defect 

 most common of the wing varia 

 nature. This mutation invol 

 fourth branch of the radius 

 pie genetic factors are invo 

 ture influences the trait, th 

 being correlated with higher 

 Whiting, 1932a). A single ge 

 in breeding experiments, poss 

 wild-type stock (P. W. Whit 

 isolated and found to give 

 phenotypically defective unde 

 tions, 30° C, Defective is o 

 and fertility. (Discarded) 



ive is one of the 

 tions occurring in 

 ves a break in the 

 vein (R4). Multi- 

 Ived, and tempera- 

 e greater defect 

 temperature (P. W, 

 ne occurring early 

 ibly derived from 

 ing, 1924b}, was 

 about 95 per cent 

 r standard condi- 

 f normal viability 



WRINKLED, w (wings). Wrinkled occurred in a 



female, and is the result of a mutant factor 



causing difficulty in shedding pupal integument 



(P. W. Whiting, 1926b), As a consequence ir- 



59 



