vi INTEODUCTION. 



perhaps (in opposition to the views urged by the late Mons. PeyerimhofF in the 

 * Annales do la Societe Entomologique de France,' 1876, p. 577) he depends too 

 much upon the presence or absence of the costal fold for generic division, his 

 critics have not yet produced any system of classification which can be said 

 to supersede that of Heinemann, or to depart from the general guiding principles 

 which he laid down. Many genera which have been perhaps linked together by 

 the discovery of intermediate forms, or which have not presented in themselves 

 sufficiently strong permanent characteristic differences, besides some few, perhaps, 

 which might possibly have remained clearly defined and acknowledged, seem to 

 have been merged by him under more comprehensive generic titles, in which 

 they have sunk to the rank of subgenera. It may be objected to this system that 

 distinctions sufficient to separate the numerous subgenera are really equally 

 sufficient to be of full generic value. 



Whilst following the method of determination laid down by Heinemann, I 

 have ventured so far to depart from his system of arrangement for the purposes of 

 this volume as to recognize his subgenera as genera, thus avoiding that departure 

 from' strict binominal nomenclature which is involved in the practice of writing 

 names in such a form as '■'■ ToHfix [Caccecia) rosaceana, Harris;" and had I been 

 following it less faithfully I should have been much disposed to break up the 

 large genus Pcedisca into at least three separate divisions, which could, I think, 

 be clearly defined. 



Heinemann uses Grapholitha, H.-S., as one of the subgenera of Grapholitha, 

 Tr. Since Heinemann's limitation of the subgenus is not exactly coextensive with 

 Herrich-Schafier's limitation of the genus, I have preferred to speak of Gra'pho- 

 litha (H.-S.), Hein,, as expressing that Heinemann's subgenus is adopted as distin- 

 guished from the larger and more comprehensive genus of Treitsche. 



An additional reason for adopting Heinemann's method seems to be presented 

 by the fact that Prof. C. H. Fernald, of Maine State College (who is, I believe, 

 about to publish a complete list of the North-American Tortricidce), has been 

 guided in his investigations by the rules laid down by Heinemann ; and as the 

 present volume treats exclusively of North-American species, it will be found 

 convenient that their classification corresponds, as far as possible, with that which 

 has been adopted in compiling such a national catalogue. 



