424 [November 



of the spines, and in having four sanguineous stripes instead o^ seven 

 dark green ones. It cannot therefore be ruhicunda, and hence it would 

 seem to follow that it must be either bicolor or some species hitherto 

 undescribed both in the larva and imago states. It is observable that 

 Dr. Harris describes the larva of peUucida, of which he professes to 

 have seen only a single specimen, as " pea-green, shaded on the back 

 and sides with red, longitudinally striped with very pale yellowish 

 green, and armed with black thorns," and adds that " it resembles 

 senatoria in everything but color," whence it may be inferred that it 

 has about seven dark stripes, instead of four dark stripes, as peUucida 

 is described by Dr. Fitch. I strongly suspect that Dr. Harris described 

 the larva of ruhicunda as the larva of peUucida, taking the darker 

 green as the ground color and the paler green as the color of the 

 stripes, instead of vice versa as in Mr. Lintner's description of ruhi- 

 cunda. In any case Dr. Harris's description of the larva of peUucida 

 differs altogether too widely from Dr. Fitch's description to apply to 

 the same species ; for I observe that in the larvsd both of senatoria and 

 stigma the range of variation is by no means wide, and consequently, 

 according to what I have called the " Law of Equable Variability," we 

 may presume that the range of variation will not be wide in the larva 

 of the closely allied peUucida. (Proc. Eat. Soc. Phila. II. p. 213.)* 

 There is another reason, of no great weight perhaps, but still of some 

 weight, why my two larvjie cannot belong to peUucida — the only known 

 N. A. species, except bicolor, to which they can with any probability be re- 

 ferred. It is often, though by no means universally, the case, that when 

 bright colors occur in the larva the same colors occur also in the imago. 

 For example, the larva of Deiopeia heUa Drury is said by Drury to be 

 yellow and white dotted with black, like the front wings of the imago; 

 the larva of Papilio Asterias Fab. is marked with yellow and black 

 like the imago ; and merely from studying the colors of the imago, I 

 foretold that the larva of Dnryphora lO-lineata Say " would probably 



*I see from the Preface to the Iconographie des CoquUles Tertiaires, published 

 in 1845 by Prof. Agassiz (p. 4), that he practically recognizes the validity of 

 this Law in Conchology; and I learn from a Botanical article in the Nat. Hist. 

 Review (1863, p. 192). that very many Botanists practically recognize it at the 

 present day. Important, however, as the Law is. it does not appear to have 

 previously received any name. 



