24 COLORATION IN POLISTES. 



that is, if the segment is marked dorsally with a lateral yellow spot 

 whose borders are tinged with ferruginous, inspection of the ventral 

 side will invariably reveal the yellow spot contracted or entirely obscured 

 by a darker color. 



The correlation between the two surfaces may be shown in another 

 way, as follows : For this purpose 100 melanic females constituting Lot i 



\ 



FIG. ii. Condition of the females from southeastern Wisconsn, with reference to the ventral 

 abdominal markings. Innermost circle (a) represents type of marking nearest to that 

 typical for the second abdominal segment of the dorsum. (PI. I, fig. 13.) 



a, b, c, d, a, b', c", d. Transitions to the maximal melanic condition. 



a, b" , c". Transition to maximal xanthic condition. 



a, b"', c"', d'". Transition to a melanic condition, in which the prevailing tone is fuscous. 

 (PI. I, fig. 5.) 



were selected, i.e., those in which the dorsal borders were narrow and 

 the lateral spot absent or tending to become obsolete. Lot 2 contained 

 100 xanthic females, i.e., those in which the dorsal borders are broad 

 and lateral spot is large, yellow, or yellow and ferruginous, and confluent 

 with the borders. The characters of the specimens with reference to 

 the ventral surface were then made out. 



