COLORATION IN POLISTES. 



57 



CORREI^ATION BETWEEN PIGMENTATION OP SECOND ABDOMINAL, SEGMENT AND 

 THE SEGMENTS POSTERIOR THERETO. 



In general, the melanism in the more posterior segments advances 

 at least one stage over that of the second segment — that is, when a 

 specimen would be put in class o, with reference to the second segment, 

 reference to the remaining segments would place it in class i ; the 

 yellow margin would be obsolete ; when the second segment belongs 



Fig. 19.— Correlation between pigmentation of the second abdominal segment and that of the 

 metathorax ; 100 specimens from Cold Spring Herbor, N. Y, Classes for the abdom- 

 inal segment same as in determination figured in fig. 18. Classes for metathorax : 



1. Red-brown, with or without parallel yellow stripes. 



2. Red-brown, with black in the median furrow and perhaps in two points at the anterior end 

 of the red zones which border the furrow laterally. 



3. Black and red-brown about equal in amount. This condition is brought about by the spread 

 of the black from the points above indicated. 



4. Black extended to obscure all but two red-brown lines, which occasionally are tinged with 

 yellow. 



5. Entirely black, with occasional slight traces of yellow in the zone of median stripes. 

 Distribution of material with respect to second abdominal segment represented by continuous 



line ; distribution of material with respect to metathorax represented by dotted line. 



to class I the remaining ones belong to class 2 — that is, they have a 

 line of pigment at the base. 



In class 2 the remaining segments have a broader band or a deeper 

 black triangle than has the second. They rarely have the red-brown 

 in the form of a large oval spot. 



This condition is represented graphically in figs. 27, 24, and 25. 

 In fig. 27 the cur\'e for the second segment of the Long Island material 



