GENETIC STUDIES ON FLOUR-MOTH 429 



and type. The ratio appears like that produced by the crossing 

 of a heterozygous dominant with a recessive but with some diffi- 

 culty in classifying certain of the individuals. A pair of definitely 

 sooty moths from this fraternity which probably lacked dark 

 mid-area produced 30 definitely sooty and 6 definitely type. 



A type male paired with a sooty female produced 25 sooty, 

 10 males and 15 females; 17 type, 10 males and 7 females, and 

 6 moths of intermediate appearance, 3 males and 3 females. A 

 pair of these sooty moths produced a fraternity of 28 males and 

 30 females among which the gradation from sooty to type was so 

 continuous that I found it impossible to make any good separa- 

 tion. A pair of these that showed rather dark wing-base pro- 

 duced a fraternity of 15 males and 14 females showing gradation. 

 A pair of the type moths from the original fraternity produced 



52 moths of typical color and these produced in the next gener- 

 ation 105 of similar character. It is possible then to extract 

 type from an intergrading stock. 



A pair of type moths produced 36 males and 38 females which 

 showed considerable variability in the pigmentation of the base 

 of the wings. None of them were dark enough to be called sooty, 

 however. A pair of moths having wings with rather dark bases 

 were selected and produced progeny that were classified as type, 

 10 males and 8 females, and moths with rather dark wing-base, 

 4 males and 6 females. The gradation was really continuous, 

 but the evidence shows that the tendency toward darkening of 

 the wing-base is hereditary. Such a tendency, occurring in a 

 culture that is segregating sooty as well, would be very con- 

 fusing. It appears, then, that a hereditary tendency to darken 

 the base of the wing, as well as the variation known as dark mid- 

 area, may tend to obscure the distinction between soot}^ and 



type. 



In the fraternities discussed below, the distinction between 

 sooty and type was perfectly clear, indicating that the confusing 

 factors were not present. 



A sooty male paired with a type sister produced 111 sooty, 



53 males and 58 females. Heterozygous Fi moths when paired 

 produced 134 sooty, 61 males and 73 females, and 70 type, 35 

 males and 35 females, the expectation being 153 to 51. 



