PLATE i 
A. —Setae of A phis maidis penetrating a young corn leaf. The black arrow points 
to the thin spot in the cuticular covering of a stomate guard cell where the setae 
entered. 
B. —Continuation of the same setae shown in A. The white arrow points to the 
tip of setae lying in the phloem. This is the typical condition. 
C. —Setae entering between epidermal cells. 
D. —Same setae shown in C. The setae bundle has encountered a xylem element. 
