MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 9 



the type species is tlic most modified, that most unlike its cougeuers/uuless, as is often tbe case, it 

 happens to have beeu the first one of its genus to have been discovered and described. 



We have thought it better and more phikisophical to begin with tliat species whose larva is 

 the most simple and geueralized, and then arrange in their natural order those whose larvte 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 lehthyura, for example, the larva of /. apicalia 

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

 ings of /. inclusa and albosigma. I have therefore supposed this to have been the first species to 

 have evolved, and this decision is supported by the wide distril)ution of the species and the rather 

 large number of varieties and subvarieties into which the form has beeu broken up. 



In the case of the imago, that species which has plaiu wings without complicated 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 the simple attempt will lead to a more careful scrutiny of the larval character- 

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

 that of course is the aim in such work. Of course the systematic part of this or any other work 

 of the sort is a necessary i)reliminary 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 text-books and other works of tlie sort, still 

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

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

 Such lists and works would have a far higher educational value and lead to much better mental 

 training if such compilers could have had some knowledge of the immense impetus given to the 

 science and the new way of dealing with systematic zoology which has resiilted 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 abdominal segments, because the former usually 

 differ 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 

 infraspiracnlar 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, larvre, 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 coDperation that we shall arrive at a fair knowledge of the transfornuitions 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 nuiseums mentioned below, whose 

 hearty cooperation I now acknowledge. 



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

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

 of years of labor while residing iu Illiuois, 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 larva; as well as moths for study and illustration. lie has also 

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



' It is earuestly hoped that anyone receiving this memoir will kindly reciprocate by sending the eggs and larvte 

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

 July and Auiiust, at Brunswick, Me. We still lack the eggs and young larv.-e of Ellida, Lophodonta, Drymonia, 

 and Notodonta. 



