274 PROCEEDINGS OF THE ACADEMY OF 



OBSERVATIONS ON CHANGE IN STRUCTURE OF A LARVA OF DRYOCAMPA 



IMPERIALIS. 



BY THOMAS G. GENTRY. 



I desire to call the attention of the Acadeni}' to some import- 

 ant stnu'tural changes in a larva of Drijocampa imperialism Avhich 

 came under m}' observation during the early part of last August, 

 as they show sufficient reasons, in my opinion, for the withdrawal 

 of the imperialis of Drury, from the new genus of Dryocampa, 

 and its reinstatement iu the old one of Ceratocampa. Besides, 

 they afford additional proofs to the many which have already 

 been noticed by naturalists, of the incompetency of Darwin's 

 theory of natural selection in every case, to account for the origin 

 of species, by minute, indefinite, fortuitous variations, without 

 the aid of other and more important causes. 



In this vicinity, during the last four years, I have found the 

 larva of Dryocampa imperialis feeding principally upon the leaves 

 of Juniperits communis and J. Virginiana^ and occasionally upon 

 some few species of Pinus ; but prior to the above time, so far as 

 I have been able to determine, it has never been observed feeding 

 upon the various species of Juglans, etc., in company with the 

 larva of G. regalis. 



At the time above mentioned I found the larva of what I 

 supposed to be the C. regalis feeding on an English walnut. I 

 felt no little surprise at the unusual appearance whicli it pre- 

 sented, and I was at first somewhat dubious, whether to refer it 

 to G. regalis or D. imperialism as it contained marked characters 

 of both. If it had been in one of its earliest stages, it would not 

 have excited wonder since the young of the two bear such a close 

 resemblance to each other; but this specimen had attained the 

 period of its final change. In size, color, and the nearly equal 

 development of the spinous projections of the dorsal surface of 

 the thoracic segments, it agreed Avith C. regalis; in the diminu- 

 tiveness of the abdominal projections, and in the moderately sized 

 hairs which rather closely invested the worm upon the superior 

 and lateral surfaces, it agreed with D. imperialis. I might add 

 that the chrysalis approximates the genus Ceratocampa in general 

 appearance, and in the conformation of the terminal appendage 

 or spine, more nearly than Dryocampa. 



