COLORATION IN POLISTES. 



The distribution of material is as follows : 



29 



These three classes are fairly well delimited, but of course transi- 

 tions occur. For example, in Class C the stripe may not in all cases be 

 quite so long or so wide as the median stripe, and in Class A there is 

 occasionally a faint trace of yellow in the lateral region (fig. 15). 



FIG. 16. Correlation between size of metameric spot and width of terminal border of second 

 abdominal segment ; 100 xanthic and 100 melanic individuals, including males and 

 females. As before, dotted line represents xanthic ; continuous line, melanic indi- 

 viduals, a, width of border 0.3-0.5 mm. ; b, width of border 0.5-0.7 mm. ; c, width of 

 border 0.7-0.9 mm. 



FIG. 17. Correlation between the amount of yellow in the abdomen and that in the clypeus of 

 female. Lots i and 2 as before, but males excluded, a, clypeus with broad black 

 spot- in the center, extending half or all the way to margin ; b, black area extends 

 less than half way to margin ; c, black restricted to a mere dot, or entirely absent. 



With regard to the width of the median stripes of the metathorax, 

 these lots fall into the following classes : 



Class A, width of stripe in its broadest zone o to 0.3 mm. 

 Class B, width of stripe in its broadest zone 0.3 to 0.6 mm. 

 Class C, width of stripe in its broadest zone 0.6 to 0.9 mm. 



