1915] Adaptions to Arid Conditions 367 
The Membracide are few in number in the arid regions, 
especially of the more strictly tree and shrub inhabiting genera 
contrasted with the weed and miscellaneous feeders like the 
Stictocephaline. This may partly be accounted for by the 
scarcity of trees in these regions, but probably the climatic 
factor is also of importance. The fact that certain forms 
Fig. 2. A stalk of Heracleum showing the leaf sheath. 
Fig. 3. Section of leaf sheath with larve of A phrophora and their froth. 
do not follow their respective trees into the arid region and 
more especially the peculiar change in habit of two eastern 
species mentioned below, indicate that the aridity is a limiting 
factor. 
The larve and adults of Vanduzea vestita Godg live together 
in colonies on the lead plant Amorpha canescens Pursh in the 
Mississippi Valley and are often seen congregated on the 
