THE GENETICS OF HABROBRACON JUGLANDIS ASHMEAD 



ing amounts and under different conditions gives 

 rise to different colors and intensities of 

 color. Chromogen and enzyme I (and 02) are nec- 

 essary for any color production ; acting together 

 they produce yellow. Enzyme II has no effect 

 alone, but in combination with I oxidizes chro- 

 mogen to black and is effective below the thresh- 

 old of I alone. In the absence of I no color 

 can be produced, in the absence of II, no black. 

 Figure 18, is an attempt to express in simple 

 form the maximum potentiality of each genetic 

 type in respect to each enzyme. Wild-type is 

 used as a standard. Quantity of enzyme I is rep- 

 resented on the left, of II on the right. Any 

 environmental condition which lowers the ex- 

 pression of II increases the expression of I. 

 Lower temperatures change the black pigment of 

 the lemon mutant less strikingly than that of 

 wild-type or black. The black areas never be- 

 come as intense or widespread, but in spite of 

 this there is a striking lightening of yellow. 

 This fact taken together with the lighter gen- 

 eral color at higher temperatures and the ob- 

 served transparency of thoracic cuticle at both 

 temperatures suggests a deficiency of enzyme I. 

 There is too little of I to combine with II to 

 form as much black as in wild-type and likewise 

 too little to produce the full amount of yellow 

 even at high temperatures (A. R. Whiting, 1939b). 

 The effect of temperature on the eye colors, 

 carrot, maroon, and the combination, carrot-ma- 

 roon, has been tested (David, 1938). Limited 

 experiments have also been made with the eye 

 color, cantaloup, and with the body color, lem- 

 on. The temperature ranged from 37° C. to 15° 

 C. Except for cantaloup, which showed little_ 



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