34 2 KATHARINE FOOT AND E. C. STROBELL. 



PLATE IV. 



These photographs of the ventral surface of 41 male insects are of specimens 

 preserved in pure glycerine in test tubes. The genital segment of each insect has 

 been pulled out and cotton inserted behind the segment to hold it in position to 

 show the entire ventral surface. 



The magnification is about iH diameters. 



PHOTO 61. Seven male specimens of E. variolarius, showing the typical black 

 spot on the genital segment. These are the same specimens which were photo- 

 graphed for our report of the cross between E. variolarius and E. servus. 



PHOTO 62. Seven male specimens of E. ictericus, showing that the spot on the 

 genital segment which is so pronounced in E. variolarius (photo 61) is only faintly 

 indicated in E. ictericus. 



PHOTO 63. The E. ictericus male that fertilized the E. variolarius female of 

 the first cross, p. 324. Photo 9 show" the intromittent organ of this insect. 



PHOTO 64. The ictericus male that fertilized the Fi female hybrid that was 

 raised from the cross E. variolarius 9 X E. ictericus d 1 . 1 From this back cross 

 (see Record, p. 326) 195 eggs were deposited and 177 of these hatched, 149 were 

 reared to the winged stage (76 males and 73 females). 



PHOTOS 65 to 69. Twenty-five specimens of the 76 males from the above 

 mentioned back-cross. 



A comparison of these 25 specimens with photo 62 shows the influence of the 

 E. variolarius grandmother on the genital spot, for a few of these specimens have 

 the genital spot almost as pronounced as that of the pure variolarius species and in 

 the majority of the specimens the spot is stronger than that of the pure ictericus 

 individuals of photos 62 and 63 and of the pure ictericus parent (photo 64). The 

 ictericus inheritance is shown in those individuals which have merely a faint indi- 

 cation of the genital spot, e. g., the lower three insects of photo 67 and the lower 

 two of photo 68. 



1 The three apparently pigmented spots on the genital segment of this speci- 

 men are misleading, they are in fact, a slight discoloration of the segment and 

 not a pigmentation. The genital spot of this individual is like that of the lowest 

 specimen of photo 67. Photo 10 shows the intromittent organ of this insect. 



