14 MEMOIRS OF THE NATION' AL ACADEMY OF SCIENCES. 



While the origin of the eruciform larviB of the CeraiiiDycidM', Ourculioiiidte, Scolytidte, aud' 

 other wood-boring and seed-inhabitinji' and burrowing Coleopterous larva- in general, is i)laiuly 

 attributable to adaptation to changed modes of life, as contrasted with the habits of roving, 

 carnivorous, cauipodeiform larvie, it is uot so easy to accouut for the origin of the higher metabolous 

 orders of Diptera. Lepidoj)tera, and Ilynienoptera, whose larvi>' are all more or less eruciform. We 

 are forced to adoi)t tlie supposition tliat they have independently originated from groujis either 

 belonging to the Neuroptera (in the modern sense) or to some allied but extinct group. 



iiestricting ourselves to the Lepidoptera; as is well known the Lepidoptera are now by some 

 believed to have descended from the Trichoptera or from forms allied to that group. We should, 

 however, prefer the view that the Lepidoptera, Trichoptera, aud Meco])tera had a common origin 

 from some earlier, extinct group. The similarity of the imagines of certain of the lower Tuieiua 

 and certain of the smaller Trichoptera is certainly very marked, the most significant feature being 

 the fact that the mandibles in the two groups are either absent or minute aud rudimeutary. 



We have attempted, however,' to show that the larva- of the l'anorpid;e, j udging from Brauer's 

 figures and descriptions, are much nearer in shape and ornamentation to caterpillars thau to 

 case worms. Hence, it seems to us probable that the ancestral or stem form of the Lepidoi)tera 

 was probably a now extinct group, somewhat intermediate between the Mecoptera (Pauor])idiE) 

 and the Trichoptera. 



The jirimltire caterpillar. — We would suggest that the earliest type of Lepidopterous larva 

 was allied to some Tineoid which lived not only on laud but on low herbage, not being a miner or 

 sack-bearer, as these are evidently secondary adaptive forms. It is evident, when we take into 

 account the remarkable changes in form of certain mining Tineoid larvai described and figured by 

 Chambers- and by Dinimock,' tiuit the fiattened, footless, or nearly apodous mining larva- of the 

 earlier stages are the result of adaptation to their burrowing habits. The generalized or jirimitive- 

 form of the first caterpillar was, then, like that of Tineoid larvie in general, and was an external 

 feeder rather thau a miner. The body of this forerunner or ancestor of our present caterjjillars 

 (which may have lived late in Carboniferous times, just before the appearance of flowering plants 

 and deciduous trees) was most probably cylindrical, long, and slender. Like the Panorpid larviie, 

 the thoracic and abdominal legs had already becom difiereutiated, and it differed from the larvie 

 of Panori)ids in the plantie of the abdominal legs being provided with perhaps two pairs of 

 crochets, thus adapting them for creeping witli security over the surface of leaves aud along twigs 

 and branches. The prothoracic or cervical shield was present, as this is apparently a primitive 

 feature, often reappearing in the Noctuidii?, and sometimes in the Bombycina, and always jiresent 

 in the boring larvre of the Uepialidie and the Cossid;e. 



As tactile hairs, defensive or locomotive setie, and spines of manifold shapes occur in worms, 

 often arising from fleshy warts or tubercles, it is reasonable to assume that the piliferous warts of 

 lei)idopterous larvte are a direct heirloom of those of the vermian ancestors of the insects. In our 

 primitive caterpillar, then, the piliferous warts were present, eventually becoming arranged as 

 they now are in ordinary Tineoid, Tortricid, Pyralid, Geometrid, and Xoctuid larva'. 



Origin of the ijreen color of caterpillars. — The cuticle may at first, as in that of caseworms and 

 Panorpid larvae, have been colorless or horn colored. But soon after habitually feeding in the 

 direct sunlight on green leaves, the chlorophyll ^ thus introduced into the digestive system aud 

 into the blood and the hypodermal tissues would cause the cuticle to become green. Afterwards, 

 by further adaptation and by heredity this color would become the hue in general common to 

 caterpillars. Moreover, some of the immediate descendants of our primitive caterpillars were 

 ])robably lighter in hue than others ; this was probably due to the fact that the lighter-colored ones 

 fed on the pale-green underside of the leaves, this difference becoming transmitted by heredity. 



' Third Report U. S. Eutomologictl Commiasion. Genealogy of the Hexapoila, pp. 297-299, 1883. Also American 

 Naturalist, Sept., 1883,932-945. 



^American Entomologist, iii, 1880, 255-202; Psyche, ii, 81, 1,(7-227; iii, 63, 135, 147; iv, 71. Refers to the larvie- 

 of the -'Gracilaridie " and "Llthocolletid;e'' together with Phyllocnistis. 



'Psyche, iii, Aug., 1880, 99-103. 



•■Seo the important and quite conclusive footnote hy Professor Meldola ou p. 310 of Weismaim's Studies in the 

 Theory of Descent, Vol. i ("I have already given reasons for suspecting that the color of green caterpillars may be- 

 due to the presence of chlorophyll in their tissues, Proc. Zool. Soc, 1873, 159. — R. M."). 



