Article I. — The Dnigon-Jiies (Odonata) of UJinois, with 

 Descriptions of the Imii/atiur Stages. Part I. Petalnrithe, j'f'Jseh- 

 nidif', and (iowj)hid(f\ By James CI. Needham and Charles A. 

 Hart. 



Introduction. 



The present paper is the combined product of studies made 

 by the authors upon the collections of the Illinois State Labo- 

 ratory of Natural History, including those of the Biological 

 Station at Havana, and by Professor Needham on his private 

 collection. The state collections comprise the results of many 

 years' w^ork in all parts of Illinois, including five successive 

 years of field observation and collection at the Illinois Biolog- 

 ical Station on the Illinois River at Havana ; specimens ob- 

 tained by Professor H. Garman from the Mississippi and related 

 waters at Quincy, 111. (Clarman, '90); a large series from the 

 small lakes of northeastern Illinois ; and collections made by 

 Professor Forbes in Yellowstone Park and its vicinity (Forbes, 

 '93) and from lakes Greneva and Delavan, Wis., under the au- 

 spices of the U. S. Fish Commission, Professor Needham's pri- 

 vate collection used in the preparation of this paper contains 

 many Illinois and New York species, reared by him to the 

 imago, and others contributed by correspondents, particularly 

 by Mr. F. G. Schaupp in Texas, Mr. Adolph Hempel in Florida, 

 and Mr. F. C. Willard in Arizona. The preparation of the in- 

 troductory matter, biological discussions, and keys to the 

 nymphs has devolved upon Mr. Hart, while the descriptive 

 matter, with a few exceptions, was prepared by Professor 

 Needham. 



We are indebted to Mr. C. C. Adams for abundant data on 

 the occurrence of the imagos in Illinois derived from his large 



