ME]\r()IlJS OF THE NATIONAL ACADEMY OF SCIENCES. 29 



the larval Ibriiis, espet-ially of tiio. carliis.st stages, it is not diliicAilt to ('oustnict a geuealosical 

 tree of tlie subfamilies Ileterocainpiiue and Ceruriiia'. Wbeu taking into account the larval stages 

 of the entire family, even with our present imperfect knowledge, it is easy to see that Dataua 

 stands at tiie base, is tlie more generalized primitive form, and was perhaps the first to diverge 

 from the stem-form of the family. 



Tlit> tii'st author to cali attention and at the same time to treat in a philosophic way of what 

 he has called "the iucongrnence of form relationslii[), between larva' on the one hand and imagines 

 on the other" is WeismanUjin his well-known work entitled Studies in the Theory of Descent. In 

 Chapter II of the second volume, entitled "Does the form i-elationship of the larva coincide with 

 that of the imago?" he ])oiiits out certain incongruences between the larval and adult characters. 

 ITe claims that "neither the group of Microlepidoptera nor those of the Xoctiiinn, Homhijcina, 

 8pliiiH)ina, and RhopaJocrra can be based systematically on larval characters," adding the quali- 

 fication, "Several of these groups are indeed but indistinctlj- defined, and even the imagines 

 pi'esent no common characteristics by which the group can be sharply distinguished.'' Within the 

 families, however, he states: "There there can be no doubt that in an overwhelmingly large 

 majority of cases tlie phyletic development has proceeded with very close i)arallelism in both 

 stages; larval and imaginal families agree almost completely. On the other hand, "in the butter- 

 flies a perfect congruence of form relationship does not exist, inasmuch as the imagines constitute 

 one large group of the higher order, whilst the larviie can only be formed into families." But in 

 this case Weismanu does not seem to be aware that the imaginal Ehopalocera as such is quite an 

 artificial group, and that the imaginal families recognized by Bates, Scndder, aTid others have 

 perhaps more eqtiivalent, congruent, or noudivergeut larval forms than his remarks would seem to 

 imply. 



But without attempting to enter into an exposition or criticism of Weismann's general 

 statements, his whole discussion being most suggestive and stimulating, we will turn to what he 

 says of the Notodontida; : 



Au especially striking case of iacougnience is offered l)y the family Xotodonlldfr, imiler which Boisdiival, 

 depending only on imaginal characters, united genera of which tho larva' dili'ered>to a very great extent. » * » 

 In fact, in the whole order Lepidoptera there can scarcely lie found associated together such diverse larva- as are here 

 placed in one imago family. 



He then refers to the short cylindrical cateriiillars of Cnethocampa, which, however is not a 

 Notodontian, but a Lasiocampid. He then briefly refers to the larvte of Harpyia (Cerura) and the 

 caterpillars of Stanropus, Hybocampa, and Notodonta. Without g'ving further attention to the 

 family, he returns to the butterflies. This family, then, presenting "an especially striking case of 

 incongruence," we will briefly discuss, referring the reader for fuller details to the figures on the 

 plates. 



In the first jdace, as a matter of fact, the more one becomes familiar with the Lepidoptera 

 and their larval forms the easier it is to distinguish the larva' by their "family" characteristics, 

 premising, however, that the term family is of very uncertain meaning, and that different 

 authors differ as to what to call a family as much as they do what to designate a species. But 

 no one, we think, neeil to err in correctly picking out or identifying any Bombycine larva except, 

 perhaps, a few Notodont larva', which are liable to be confoitiided with certain Thyatirida', and 

 the hairy NoctuidiB, but even then a careful examination will show family differences even when 

 adaptation and modification have nearly bridged over the fundamental differential characters. 



In this work I have divided the family into seven groups, which may be for convenience 

 regarded as so many subfamilies. I was first led to do so by the larval characters alone, but 

 found that this classification would also apply in general to the moths, so that there proved not 

 to be so much incongruity as was expected. There appear to be, then, seven larval subfamilies 

 and seven imaginal subfamilies. Others may not agree with this view, but it is the most rational 

 classification I have been able to make. 



Beginning with the most simple forms of larva, those of the GlupMsina\ which, both as 

 regards those of the Old and New World, are tolerably constant, the adults certainly differ notably 

 from those of other subfamilies, as also do the larvie and impai. 



