163 



used his anatomical nomenclature, for, as has already been pointed 

 out by Lundbeck in his "Diptera Danica", Brauer has erred in this 

 paper in the interpretation of different parts of both larvae and pupae. 

 These misinterpretations are not emphasized herein, as the present 

 writer believes that in undertaking original vi^ork such errors are likely 

 to occur, and that in viewing the results of the efforts of authors we 

 ought to adopt a perspective that permits a correct appreciation of the 

 ditliculties under which the work was done. By this means we shall 

 arrive at an estimate of the infinitesimal nature of existing blemishes 

 in comparison with the immense advantages afforded to succeeding 

 workers by a perusal of the author's published results. The present 

 paper is presented without any foolish assumption of infallibility, and, 

 as already stated, with a view to adding to the knowledge we already 

 possess of the early stages of North American Diptera. 



In order to keep the size of the paper within as small a compass 

 as possible, descriptions of species published by the writer in previous 

 papers are not reproduced, but citations are uniformly given to facili- 

 tate reference to them. 



ACKNOWLEDGMENTS 



I have to acknowledge the assistance rendered me in this study 

 by the loan or gift of material as follows: from Dr. E. P. Felt, State 

 Entomologist of New York; from W. L. McAtee, of the U. S. Bureau 

 of Biological Survey; from J. J. Davis and J. A. Hyslop, of the U. S. 

 Bureau of Entomology; from C. W. Johnson, of the Boston Society 

 of Natural Historv; and from Dr. R. D. Glasgow, of the University of 

 Illinois. In 1890-91 Dr. S. A. Forbes obtained a large amount of 

 material from the streams and lakes in Yellowstone National Park, 

 some of which represents genera and species of Diptera not in our 

 collections from Illinois, and these have been used as a basis for con- 

 tributory descriptions. Most of the material from the Illinois River 

 which I have studied in this connection was collected by Mr. C. A. 

 Plart, and some of it was used bv him in preparing his paper on the 

 Entomology of the Illinois River*. Several of the species discussed 

 or described were obtained bv W. P. Flint and D. K. McMillan in 

 the course of their field work for the State Entomologist's office. 



HABITS AND HABITATS OF SPECIES 



Under family headings and very frequently in the discussion of 

 genera I have given notes upon the habits of larvae and imagines, 



*Bull. 111. State Lab. Xat. Hist., Vol. 4, Art. VI. (1895) 



