MEMOIRS OF THE NATIONAL ACADEMY OF SCIE:N^CES. 9 



the type species is the most modified, tliat most unlike its coiigeiicrs/uuless, as is often the case, it 

 happens to have been the first one of its jionus to liave been discovered and described. 



We have th»n!;ht it better and more phih)Sophical to begin with tlnit species whose larva is 

 the most simple and generalized, and then arrange in their natural order those whose larvie are 

 more and more specialized or modified, as regards the number and variety of their markings, or 

 the complexity of their armature. In the genus Ichtliyura, for example, the larva of I. apicalis 

 (van) is the most simple and generidized, not having the higli tubercles and bright varied mark- 

 ings of /. indusa and (dbvs'Kjma. 1 have therefore supposed this to have been the first species to 

 have evolved, and this decision is supported by the wide distribution of the species and the rather 

 large nundjer of varieties and subvarieties into whicli tlie fiirm has been broken up. 



In the case of the im;igo, that sjiecies whicli has plain wings without comiihcated bars and 

 spots is more primitive than those with more complex markings. 



This course may at times lead to error and uncertainty, and involve more or less hypothesis 

 or guesswork, but tlie simple attempt will lead to a more careful scrutiny of the larval character- 

 istics, and to a profoundcr, more thorough, and better knowledge of the biology of the genus, and 

 that of course is the aim in sncli wcu'k. Of course the systematic i)art of this or any other work 

 of the sort is a necessary preliminary to all other higher endeavors to a complete history of the 

 group from a morphological and biological point of view. 



On this account it is, we think, a great pity that some of the compilers of our check lists of 

 Lepidoptera and other insects, and of our zoological textbooks and other works of the sort, still 

 persist to cater to the tastes, rather than true needs, of amateurs and collectors by beginning at 

 the wrong end, i. e., with the " highest" forms rather than with the "lower" or more primitive. 

 8nch lists and works would have a fiir higher educational value and lead to much better mental 

 training if such compilers conld have had some knowledge of the immense im[)etus given to the 

 science and the new way of dealing with systematic zoology which has resulted from the labors 

 of Darwin, Fritz Midler, Weismann, and others. 



In describing caterpillars, particularly those of the Bombyces, I have been particular to dis- 

 tinguish between the three thoracic and the ten abdonunal segments, because tlie former usually 

 difler from the abdominal segments in the number, arrangement, and relative size of the tubercles, 

 warts, and other markings. The warts or tubercles also are grouped into dorsal, subdorsal, 

 and supraspiracular rows (though this latter may in some cases be the subdorsal row), and an 

 infraspiracular row or series. 



In order to obtain further material to finish and to perfect this monograph of the Bombyces, 

 the author would like to obtain from collectors and students in all parts of the country, especially 

 in the Southern, Western, and Pacific States, the egg, larvte, or moths, in order to fill up gaps, as 

 well as to afford material for illustration. 



Should anyone rear any of these Bombyces, with a view to publication, I should be greatly 

 obliged for alcoholic specimens of the eggs and different larval stages, which might be sent after 

 such descriptions were published.' Such specimens would be carefully kept and returned. It will 

 only be by such cooperation that we shall arrive at a fair knowledge of the transformations of 

 this extensive group. 



This monograph could not have been prepared without generous aid from friends and cor- 

 respondents, as well as from those in charge of the several museums mentioned below, whose 

 hearty cooperation I now acknowledge. 



I am specially indebted to Prof. C. V. Eiley for the opportunity of freely examining from time 

 to time his extensive collections, so rich in preserved larvfe, both blown and alcoholic, the result 

 of yearsof labor while residing in Illinois, St. Louis, and in Washington, D. C. After presenting 

 them to the United States National .Museum, he has continued to allow me to examine the Bom- 

 byces, and loaned me specimens of larvi? as well as moths for study and illustration. He has also 

 permitted the use of numerous colored sketches, made by himself or his assistants irnder his 



' It is earnestly hoped th.at aujouc receivinj; this memoir will kindly reciiirocate hy sending the eggs aud larviB 

 of any Bombyeiue moths not herein described, packed in tin boxes, to the antUor, at Providence, R. I., or during 

 July and Auj;nst, at liruuswick. Me. We still lack the eggs and young larva- of Ellida, Lophodouta, Drymonia, 

 and Notodonta. 



