28 ME.MOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



Neuropteia, Coleoptera, Mecopteni, TiicLo]iter!i, Lopidopteiii, Dipteia, and Ilymeiioptcra, where 

 there ai-e so many and ijcrplcxing cases of incongruence or divergence in larval lornis whose 

 parents are very closely allied. 



It is worthy of ui)tice that in respect to Diptera the veteran dipferologist, Baron U. von Osteii 

 Sacken, remarks of the iiemocefons tlies: »'An arrangement of the imagoes based uixiu snch prin- 

 ciples will of necessity be Justitied by a more or less tangible correspondence in the characters of 

 their larvie. This structural correspondence, this parallelism of larviB and imagoes among the 

 Xcmoccra, suffers, as far as I know, but one exception, Myvctohia jxiUiprx and Ithyplius. In both 

 almost identical larviu produce tlies belonging to dift'erent families." (Berliner entomolog. Zeit- 

 schrift, Bd. xxxvii, 1802, Heft iv, p. 418.) In the copy kindly sent me by the author a second 

 case of Anopheles and Dixa is nu'utioued in the printed cojjy, but struck out by the author in the 

 emended copy. 



Everyone is familiar with the fact that there is a nearly similar incongruity between the larvae 

 of the MuscidiC anil the flies. Many new facts bearing on this subje(;t ai)i)eared iu Portchinsky's 

 article on the habits of the necrophagous and coprophagous larva- of Muscida-, of which an English 

 abstract by Baron R. von Osten Sacken appeared iu the Berliner ent. Zeitschrift for 1887. After 

 speaking of the wonderful power of adaptation of these larvsB to their environment, he states: 



Distinctly related species belonging to different genera issue from larv;e almost indistinguishable from each 

 other. And again closely related and almost indistinguisliable imagoes, species of the same genus, differ iu their 

 oviposition (size and number of eggs), and their larv:e follow a different law of development (as to the degree of 

 maturity the larva reaches within the body of the mother and the number of stages of development it passes through ). 



In one case even (Mnsca corviiia) larva' of the same species were found to have a different mode of (!evel())uucut 

 iu northern and southern regions of Russia. 



Here also it is evident that the cause of the incongruity is due to the fact that the larva', for 

 the tiiue being different animals from the adult, are modified by their environment, the similar 

 surroundings and habits of the larvie of quite different genera causing the larva- externally at 

 least to closely resetuble each other. Whether they are so similar in their internal organs reniaitis 

 to be seen. Dr. C. W. Stiles, who has studied so carefully by microscopic sections tapeworms of 

 externally similar form, and which can not be separated by external characters, tells me that the 

 internal organs seem to afford excellent specific and generic characters. 



Lepidopterists in general do not hesitate to base their systems of classification on the larval 

 as well as adult features. They in general regard their systetnatic arrangements of the imagines as 

 more or less provisional, and all ac^knowledge that it is immensely satisfactory, even after they are 

 pretty well satisfied with th eir arrangement of the adults of a group, whether a genus or family, 

 to work out the larval stages aiul to check their classifications based on adult features by the 

 larval characters. In matiy cases they may be led to change the position of a species or genus, 

 or to split up a genus or species. 



But, after all this, the tact that so many larva, even in the same group, are hatched with such 

 different shapes and characters; the fact that some are so much more simple and primitive than 

 others, ope;is up most perplexing yet interesting questions and problems. We may, however, be 

 able to solve these, and in the present group of Bombyces it seems to us that the different larval 

 forms, some primitive and generalized and others more or less modified or specialized, give clues 

 to the phylogeny of the groups which we confess we had not expected. 



And in this memoir we have endeavored, though often it is mere guesswork, to drop the old- 

 time method of putting the type species first and then ranging the others after it in an ill assorted 

 gioup, and have attemi)ted to begin with what has seemed to us to be the ancestral form of the 

 group, following with the later forms. This can be best accomi)lishe(l by takitig into consideration 

 the caterpillar, beginning with the generalized forms and ending with the later more modified 

 or specialized forms. In such a large genus as Heterocami)a this is not difficult to do. For 

 example, as we shall see hereafter, the larva of H. manico is as sitiqile and generalized as any, 

 while that of H. unicolor is the most modified, with its semi-stemapoda, from which Macrurocampa, 

 with its fully formed stemapoda, may have descended. And then, while Cerura, with its stemapoda 

 alike in all the species, is often or generally placed first in the group, it is evident that it was 

 descended from some Heterocampalike form through Macrurocampa. Aided by our knowledge of 



