138 



Part III. consists largely of some discussion of these prob- 

 lems, followed by an annotated list of species which it is hoped 

 may be an acceptable contribution to the knowledge of the in- 

 sect life of Illinois. A comparison of these western Illinois 

 areas with those of the northeastern part of the state is greatly 

 to be desired, as the indications are that their biotas differ con- 

 siderably, and are derived more or less from different geograph- 

 ical sources. 



In addition to the faunal studies, I have given particular 

 attention to the topography and remarkable glacial history- 

 especially with regard to the origin of the sand areas and their 

 fauna — of the Illinois River valley, nearly the entire length of 

 which I have traversed at one time or another. These subjects 

 are treated in Part I. as a preliminary to the biological studies. 



The map is adapted from Leverett ('99, PI. VI.); plates 

 XXII. and XXIII. are from photographs belonging to the State 

 Laboratory of Natural History; and the remaining plates are 

 from photographs by Mr. Gleason. 



The authors are greatly indebted toTrofessor S. A. Forbes, 

 Director of the Illinois State Laboratory of Natural History, 

 for his kindly interest and for the publication of this paper; 

 and they desire to acknowledge gratefully the cordial hospi- 

 tality and assistance of various citizens of Havana and vicinity. 



C. A. Hart. 



