50 THE UNIVERSITY OF OKLAHOMA 



Bruchus pure for tan, Dr. J. K. Breitenbecher observed a female 

 with red body color. This mutant female was mated with a normal 

 tan male by him and inbred until a inass culture pure for red was ob- 

 tained. In this race of insects the female has the usual four black 

 spots of the wild type, and the red body color of the mutation, while 

 the male is a tan phenotype but a red genotype. 



On September 22, 1921, a female was found in a mass culture 

 pure for red body color which had four red spots instead of the 

 four black spots. This mutant female with red body color and red 

 spotted elytra was mated with a male that was pure for red. After 

 several matings for homologous mutants, a culture was obtained 

 that v/as pure for both red body and red spots. 



It is of special interest to note that this character is sex 

 limited, that is, manifested only in the female. The male of this 

 strain is pure for the same factors, but every male appears tan in 

 body color and has no elytra pattern visible. This kind of sexual 

 dimorphism is known as 'sex limited,' and is often called a secondary 

 sex character. As a result of this we have two different types of 

 insects produced. 



The factor symbol for red spots may be represented by (SS) 

 and that of black spots by (ss). Then by crossing a female pure 

 for red spots (SS) with a male pure for the same (SS) the result- 

 ing offspring will every one be pure for red spots (SS). 



Experiments 



One female pure for red spots was mated with a spotless male, 

 pure for black spots. The resulting female offspring were all red 

 spotted. Sufficient data has been obtained to show that the normal 

 black spots is a Mendelian recessive to the red spotted mutation; in 

 other words the mutation is a complete dominant to the black spots 

 of the tan wild type. 



A mutant female, pure for red spots was bred to a male pure 

 for red spots. No black spotted females were obtained, but ten red 

 spotted females and nineteen tan males carrying (SS) were observed. 



When a red spotted female (SS) is mated with a non-spotted 

 male (ss) carrying black spots, their female offspring were all red 

 spotted (Ss), but the males were all non-spotted. 



By crossing the F^ males and females from the above experi- 

 ment (both of which were heterozygous (Ss) for red and Hack 

 spots) the following F^ offspring were obtained: twenty-nine red 

 spotted females whose genetic constitution may be represented as 

 (SS, Ss, and sS) nine black spotted females (ss) and twenty-two 

 non-spotted tan males (SS, Ss, sS, and ss). 



Since the red spotted character is dominant to the black for the 



