330 KATHARINE FOOT AND E. C. STROBELL. 



fluence of each parent in the transmission of the genital spot in 

 the hybrids can, therefore, be ascertained only approximately 

 and the case is further complicated in the ictericus cross by the 

 fact that in E. ictericus, unlike E. servus, a genital spot is not 

 wholly absent. 



Photo 6 1 is of seven male specimens of E. variolarius showing 

 on each genital segment, the brown or black spot characteristic of 

 the variolarius male, and photo 62 is of seven specimens of E. 

 ictericus showing the faint indication of a genital spot which is 

 characteristic of nearly all E. ictericus males. As stated above, 

 the spot, when present, is so indistinct that in most cases it is 

 easily overlooked unless the segment is pulled out and closely 

 examined, and this is perhaps why this species is described as 

 having no spot on the genital segment. Van Duzee's description 

 is as follows: 

 "Euschistus ictericus Linn. 



"Found in the Northern States and Canada across the whole 

 width of the continent. It is generally to be found on sedges in 

 swampy spots or along the borders of streams or other bodies 

 of water. It may be distinguished from the foregoing [E. vario- 

 larius] by the calloused ruga connecting the humeri which are 

 more produced than in variolarius, and the genital segment of 

 the male wants the black spot found in that species." 



Although the presence of a faint spot in ictericus is an em- 

 barrassing factor in comparing the results of the variolarius- 

 ictericus cross with those of the variolarius-servus cross, it by 

 no means obscures the fact that the evidence from the two 

 crosses is in complete harmony. 



The servus crosses demonstrated that the genital spot was 

 transmitted through the female of the first cross, and this is 

 supported by the ictericus back-cross. The inheritance from 

 the variolarius female of the first cross can be appreciated by 

 comparing the faint spot of the pure ictericus specimens of photo 

 62 with the spot in some of the back-cross offspring, for example 

 the first specimen of photo 65, the second specimen of photo 66, 

 the third and last specimens of photo 69. In these the spot is 

 almost as strong as that of the pure variolarius males and much 



1 Our Euschistus ictericus specimens were identified by J. R. de la Torre Bueno. 



