54 



COLORATION IN POLISTES. 



marked with two or four parallel yellow stripes. Variatus is the most 



melanic member of the group and connects it with the pallipes group. 



The pallipes group includes all those melanic species of intermediate 



or smaller size whose ornamentation is a rich ferruginous, more or 



FIG. 18. Relation between latitude and melanism, second abdominal segment taken as measure 

 of melanism. 



Lot i. 100 specimens collected at random near Gotha, Florida. 



Lot 2. 100 specimens collected at random near Willow Grove, Pa. 



Lot 3. 100 specimens collected at random near Cold Spring Harbor, Long Island, N. Y. 



Class o. Segment light red-brown with a yellow margin. 



Class i. Segment light red-brown, yellow margin obscure. 



Class 2. Segment red-brown, with black triangle at base. 



Class 3. Segment fuscous (nearly black), red-brown in the form of large oval spots. 



Class 4. Segment fuscous (nearly black), red-brown spots becoming obsolete. 



Class 5. Segment black, some yellow still present at the margin. 



Class 6. Segment entirely black. 



Broken line represents distribution of material from Gotha, Fla. ; continuous line, distribution 

 of material from Willow Grove, Pa. ; dotted line, distribution of material from Cold Spring Har- 

 bor, N. Y. One square equals ten specimens. 



less varied with yellow. In pattern it displays all the variation dis- 

 played in the two preceding groups, except that ferruginous tends 

 everywhere to displace the yellow. The less melanic forms occurring 

 in the Middle Atlantic States connect themselves readily with the 

 more melanic members of the following group. 



