PREFACE. 



The basis of good work in any science is a knowledge of what has 

 been done in the past. This proposition does not need argument for 

 its support, and it follows, logically, that any work which facilitates 

 the acquirement of this basic knowledge and brings together system- 

 atically and critically the results theretofore obtained will also facilitate 

 the advance of the science. The study of the North American Noc- 

 tuidae has been seriously embarrassed by the difficulty in acquiring 

 this foundation; not always because books were lacking, but often be- 

 cause the knowledge was contained in so many without an index to 

 guide the student. Since Mr. Grote's catalogue of 1874 no comprehen- 

 sive bibliographical work on this family has been published, while the 

 number of species has nearly doubled and the literature has increased 

 enormously. This state of affairs results in the formation of card cata- 

 logues or indices made by each student to facilitate his own work, and 

 gradually he becomes familiar with the knowledge published by his prede- 

 cessors. But this does not help others, and the same work is done over 

 and over again by those engaged in the same fields of study. It has also 

 been extremely difficult, even after becoming familiar with the literature, 

 to ascertain exactly what sj^ecies were really before the older writers. 

 Characters now regarded as essential were not even noted by them and 

 descriptions which, with the few species at hand, were characteristic 

 and pointed became vague and indefinite when larger material brought 

 us many and closely allied species. The greatest bugbear to American 

 Lepidopterists has been the work of Francis Walker in the catalogues 

 of the British Museum. Mr. Grote after twenty years of study in the 

 Noctuidse had failed to identify a large percentage of the species, while 

 even of the species described by Guenee forty years ago, a number are 

 still unidentified in American collections. For ten years I have been 

 accumulating material for a monograph of the North American Noc- 

 tuidiv, and have examined about all the books obtainable in Philadel- 

 phia, New York, Washington, and elsewhere, and have purchased 

 papers on the subject whenever opportunity offered. I have had, dur- 

 ing that time, unusual opportunities for studying the material in iLc 

 leading American collections, and some of the results obtained have 

 been published in my various "Contributions toward a monograph of 



the Noctuidae of Temperate North America." 



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