92 ILUNOIS BIOLOGICAL MONOGRAPHS [92 



EXPLANATION OF PLATES 



Drawings were either traced directly from the author's plates or 

 enlarged by means of the camera lucida. Magnifications are not given 

 for they did not appear in most of the original sources. The text will 

 furnish the exact size of each species so far as data were available in the 

 original publication or in the later articles. 



