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FOREWORD 



THE caddis flies, comprising the insect 

 order Trichoptera, are one of the most 

 abundant groups of aquatic insects in Illi- 

 nois. In both lakes and streams they consti- 

 tute an important factor in the food economy 

 of our Illinois fishes. For this reason, and 

 because the fauna of the order in the entire 

 Middle West was virtually unstudied, a 

 survey of the caddis flies of Illinois was 

 undertaken in 1931. 



In the summer of that year Dr. Cornelius 

 Betten of Cornell University, Ithaca, New 

 York, was employed by the Illinois Natural 

 History Survey to initiate the extensive field 

 work and acquaint the systematic entomo- 

 logical staff of the Survey with the charac- 

 ters used in the classification of caddis flies, 

 and, insofar as possible at that time, with 

 the identity of the various species inhabiting 

 the waters of our state. Since 1931, Dr. 

 Herbert H. Ross, Systematic Entomologist 

 of the Survey, has been responsible for the 

 continuation and completion of the project. 

 This final report is the culmination of 12 

 years of field work and study. Most of the 

 field work was carried on in conjunction 

 with other Survey projects, especially those 

 on the Miridae and Cicadellidae, and has 

 followed in general plan and organization 

 our other projects summarized in preceding 

 reports. Caddis flies were collected from 

 all parts of the state and at various seasons, 

 both the adult and immature stages being 

 included in the study. As the work pro- 

 gressed it became apparent that a study of 

 the entire North American fauna was neces- 

 sary to identify properly the Illinois species, 

 and much of the information so obtained 



has been invaluable in interpreting material 

 from this state. 



We are indebted to several institutions 

 and persons outside the Survey for great 

 help in these studies. In addition to Dr. 

 Betten, who has given constant help and 

 cooperation, we are especially indebted to 

 Dr. Nathan Banks of the Museum of Com- 

 parative Zoology, Cambridge, Massachu- 

 setts, for making available for detailed study 

 and lectotypic designation the types of Banks 

 and Hagen species in that institution. Per- 

 sons too numerous to mention have contrib- 

 uted a tremendous amount of information, 

 especially distributional data, in the form 

 of material submitted for identification; al- 

 though these cooperators are not listed, we 

 wish to draw attention to the significant 

 data their efforts have brought to light. 



Several members of our staff in the Insect 

 Survey Section also have contributed greatly 

 to the final manuscript. The full illustra- 

 tions of adult and larval forms, and also 

 of the cases, are with few exceptions the 

 work of Dr. C. O. Mohr, Associate Ento- 

 mologist and Artist. Dr. Mohr and Miss 

 Kathryn M. Sommerman, Artist and Ento- 

 mological Assistant, also added many figures 

 used to illustrate the keys and aid in the 

 diagnosis of genitalic characters. Dr. B. D. 

 Burks, Assistant Entomologist, and Dr. 

 Mohr were responsible for much of the field 

 work, especially the rearing work done at 

 field stations. Finally, the manuscript was 

 read and styled by the Survey Technical 

 Editor, Mr. James S. Ayars. 



T. H. Frison, Chief 



Illinois Natural History Survey 



