'^^^^ 





JOURNAL OF VARIATION. 



No. 9. Vol. I. December 15th, 1890. 



THE GENUS ACRONYCTA AND ITS ALLIES. 



By Dr. T. A. CHAPMAN. 



{Continued from page 201.) 



\CRONY CTA {Viviinia) rumicis. — I have, to some 

 extent, taken this species as the type of the sub- 

 genus Viviinia, and used it for the purpose of com- 

 paring the others with, rather because it is the most 

 abundant and easily obtained, and therefore the most con- 

 venient for the purpose, than because I have any decided 

 opinion that it is a more ancient and primitive species than the 

 others. The humps on the 5th and 12th segments of the full- 

 grown larva of riiviicis give it a peculiar outline, which is 

 further pronounced by the attitude it assumes by laying its 

 head prone and slightly raising the 5th segment off the surface 

 on which it rests, I have called this the rumicis form or out- 

 line. This form is assumed in the earlier larval stages by all 

 the other species of Viviinia, but lost again by the full-grown 

 larva. Curiously there is least of it in venosa, which in all other 

 respects, egg, newly-hatched larva, and markings of full-grown 

 larva and pupa is closer to rumicis than they. It is also perhaps 

 remarkable that the outline of the larvae of psi, tridejis, and 

 sirigosa should be so strongly that of rtimicis, though belonging 

 to a widely different section of the genus, their newly-hatched 

 larvae {psi and tridens at least), also, have the same pale and 

 dark segments as Viminia, so that it would not perhaps be safe 

 to suppose that the rumicis outline has been assumed by them 

 independently ; but I am, nevertheless, inclined to regard the 

 coincidence as due rather to a parallel variation in allied species, 

 than to a common descent from an ancestor of rumicis form. 



