8 MEMOIRS OF THE NATIONAL ACADE:\rY OF SCIEHTOES. 



4. To obtain facts regarding the ontogeny of our native species and genera which, when added 

 to what we know of the life histories of European, Asiatic, and Soutli American Bonibyces, may 

 lead to at least a partial comprehension of the phylogeny of the higher Lepidoptera, viz, those 

 above the so-called Microlepidoptera. 



The transformations of the Bombycine moths are especially noteworthy and useful for the 

 purposes we have indicated, since the group is rich in stem forms, because of its probable 

 geological antiquity, and because of the remarkable and significant diflerences presented by the 

 larv;e of many of the groups in the numerous successive stages of their larval life, these stages 

 being characteii/.ed l)y distinctive and highly modified shapes, colors, markings, and armatures. 

 These peculiarities, signalizing nearly each stage, were, we believe, evolved in direct response 

 to the changes in their environment, in their mode of life, or to changes in their food plants, 

 and the necessity of being protected through unconscious mimicry from the assaults of insects and 

 reptilian and avian enemies. 



The transformations also afibrd the clearest possible evidence of the action of what Darwin 

 calls " inheritance at corresponding periods of life," and which llivckel has tersely designated as 

 "homochrouic heredity." 



This fact, moreover, of inheritance at corresponding periods of life throws light on the 

 problem so much under discussion at the present day of the transmission of characters acquired 

 at different epochs daring the life of the individual. We have devoted a section to a discussion 

 of this question, or rather to a review of some of the facts which strongly suggest the truth of 

 this principle. 



The chai-acters, so unexpected and striking, as for those worked out in Heterocampa hiuiidnfa, 

 E. (/uitivitta, and obliquK, for exami)le, as well as numerous other of the Notodontians and allied 

 families, are plainly enough useless to the insect in the pupa or imago condition, and have evidently 

 been inherited as the result of impressions or stimuli i eceived from without at different periods in 

 the life of the caterpillar alone. 



Such cases occur in many other Arthropods, especially in the barnacles, and in the Decapoda, 

 as well as in the parasitic worms, but the causes can nearly as well be investigated in these insects, 

 which are so accessible. 



Another series of problems is opened up by a study of the mouth-parts of the Bombyces and 

 of their venation, which disclose facts intimately bearing on the genealogy of the Lepidoptera. 



In no other Lepidoptera has the agency of use and disuse, particularly the latter, been more 

 marked. While the mandibles are present in certain of the Tincina and I'liraUiUna, they have 

 totally disappeared from the so-called Macrolepidoptera, or higher and less generalized and primi- 

 tive groups. In the Bombyces, particularly the Saturnians, the maxilhe, owing to disuse, have 

 undergone great redaction, with complete loss of their original function. In another direction, 

 i. e., in the veins of the wings, there has been a reduction in their number, and this is correlated 

 with their loss of power of taking food, the great but weak wings of these colossal moths being of 

 no use in seeking for food, which they do not need; as, unlike the swift visitors of flowers, the 

 butterflies. Sphinges, and Noctnids, they are too feeble of flight to sip the nectar of dowers, or 

 too short lived to need any nourishment. 



The geograiihical distribution of the Bombyces also tends to confirm the view that they are 

 an ancient and generalized group, and to this subject we have given si)eeial attention. 



In the systematic portion of the work I have endeavored to arrange the families, genera, and 

 even the species, in accordance with the probable phylogeny of the group. I have begun my 

 account of the entire sujicrfamily with what I regard as the most primitive family. The seven 

 subfamilies of Notodontians easily fall into this arrangement; it is not difficult to perceive that 

 the Gluphisiina' and Datanina' are the most generalized, and that the Cerurime are the most .spec- 

 ialized, whether we study the larvic or imagines, though much the clearest light of course is thrown 

 upon the subject by the larvre. It is less easy to indicate the true succession of the genera, though 

 the way is made very plain in the subfamily of Ueterocampinic. 



The i)roper sequence of the species in a large genus is always difficult to make out. It is 

 obvious, however, that the old. unphilosophic method of designating such and such a sjjccies as the 

 type of a genus, and then arranging all the others under it, is a thoughtless procedure. Usually 



