PREFACE 



This, the third report upon work begun in 1900, like its 

 predecessors, marks an important advance in knowledge. The 

 first report, State Museum Bulletin 47, consisting of 230 pages 

 and 36 plates, gave the life histories of about one hundred aquatic 

 forms and characterized ten species and two new genera. The 

 most important portion of this work was the monographic ac- 

 count of the larger dragon flies (Odonata Anisoptera). 

 There were also valuable additions to our knowledge of the stone 

 flies (Plecoptera) and the May flies (Ephemeridae), 

 and the admirable account of the Caddis flies ( T r i c h o p t e r a) , 

 by Mr Betten, deserves special mention because of its careful bio- 

 logic treatment of a heretofore much neglected grouip. The 

 second report, State Museum Bulletin 68, comprised 419 pages 

 and 52 plates and was a continuation of the preceding. The 

 monograph of the Odonata is completed by an exhaustive 

 account of the smaller dragon flies (Zygoptera). Among 

 the imiportant contributions may be mentioned: The key to 

 Coleopterous larvae with an account of some aquatic 

 Chrysomelidae by Dr MacGillivray, the discussion of cer- 

 tain aquatic nemato<cerous Diptera by Dr Johannsen, and a 

 monograph on the Sialididae of the Western Hemisphere. 

 The present report is a continuation of the work, and among its 

 valuable features should be noted the monographic account of 

 our May flies, a group of great importance as food for fish. The 

 small midges, belonging to the Chironomidae, are very 

 important as fish-food and have been treated exhaustively by Mr 

 Johannsen. These three publications mark a most decided ad- 

 vance in our knowledge of aquatic forms and, with the publica- 

 tion of the monograph on stone flies now in preparation, a large 

 fund of information will be available for the student of aquatic 

 forms. 



This study, as was pointed out in the introduction to the first 

 report, has been made upon broad lines with the avowed purpose 

 of producing something of value to the fish culturist, who must 

 first of all be able to identify aquatic forms, something well-nigh 



