GENETIC STUDIES ON FLOUR-MOTH 419 



II. OBSERVATIONS, EXPERIMENTAL DATA, AND CONCLUSIONS 

 A. Description and origin of variations noted 



1. Description of variations, a. Color. During the studies 

 at Woods Hole and later the moths were examined for vari- 

 ations. It was soon noticed that there were many minor dif- 

 ferences in wing color and pattern and that these appeared to be 

 hereditary. Certain cultures produced moths darker than others, 

 while some had the transverse bands of the wings very well 

 marked. These differences persisted regardless of the nature 

 of the food. 



A few color variations were very well marked. The variety 

 shown in figure n has been called 'sooty base' or 'sooty.' The 

 base of the primaries is black and the outer margin is much 

 darkened. There is also a decided tendency for the intermediate 

 area to be lighter than in the type. The factor producing this 

 variation, S, proves dominant to type. 



Another variation tends to darken the mid-area of the pri- 

 maries, and possibly to lighten the base and outer margin. It 

 has not as yet been studied satisfactorily. In some specimens 

 it is very pronounced, but in others it grades into type. It is 

 of interest because it has an effect the reverse of sooty base. It 

 has been called 'Dark mid-area' or 'Dark.' 



A black variation, acting as a simple recessive, 6, is shown in 

 figure 0. The upper side of the primaries is black. The upper 

 side of the secondaries is slightly darkened. The under side of 

 the wings is light gray or white as in type, but some black ap- 

 pears along the costal margin. The legs and body are black or 

 gray. 



The homozygous sooty black, SS.bb, is shown in figm^e p. 



h. Size. Variations in size are probably due to lack of suffi- 

 cient food, since small moths have come out of certain crowded 

 cultures. When virgin matings of these were made they pro- 

 duced moths of normal size. 



c. Leg spines. Two spines occur at the tips of both the middle 

 and the hind tibiae and two occur in the middle of the hind 

 tibiae. They were studied in many hundreds of moths from 



