194 [November 



ON PHYTOPHAGIC VARIETIES AND PHYTOPHAGIC SPECIES, 

 with remarks on the Unity of Coloration in Insects. 



BY BENJ. D. WALSH, M. A. 



Datana ministra, Drury. (Lepidoptera.) 

 Messrs. Grote & Robinson (^Proc. &c. IV. p. 491) seem to be of opi- 

 nion, that the black larva found on the hickory may produce a different 

 species of Datana from the yellow-necked and striped larva found ou 

 the oak, the apple, &c. The objection to this hypothesis is, that a larva 

 intermediate between these two form's, viz: with the longitudinal stripes 

 but without the yellow neck, occurs, as I have already stated, {Proc. 

 &c. III. p. 403) both on the hickory and on the oak. Mr. Lintner 

 indeed tells me, that from the black larva found on the hickory he 

 reared what he considers as the D. coutracta of Walker; bat from this 

 same black larva I myself reared the normal form of ministra, (ibid.') 

 and also other forms which approximate in some of their characters 

 towards contractu Walker and towards perspicua Gr. Rob. In fact I 

 have little doubt that both these last so-called species are mere varieties 

 of ministra, based upon extreme specimens. For the distinctive cha- 

 racters, which are assigned to each of them, are not found exclusively 

 in one set of specimens bred from one kind of larva, but occur promis- 

 cuously, with all the intermediate grades, sometimes in one set of spe- 

 cimens, sometimes in another, as I shall now proceed to show. 



According to Walker as quoted by Morris (Sj/nop. p. 247) Datana 

 contractu differs chiefly from D. ministra, \st, in having narrower front 

 wings; 2?u7, in the brown wing-bands being edged externally with 

 whitish-tawny; 3;^^', in the second wing-band being nearer the first on 

 the hind border of the wing. As to the first distinctive character, I 

 have before me, a Fitch's figure of ministra, {K Y. Rep. I. PI. iv. 3,) 

 h Harris's figure of ministra, (InJ. Ins. PI. vi. Q,) c I % and dl 9 bred 

 by myself from the normal yellow-necked larva found on the oak, e and 

 /2 % and ^ and A 2 9 bred from the black larva found on the hickory, 

 and i one captured 9 . On the most careful measurements of all these, 

 I find that, making the extreme breadth of the front wing iOO, its pro- 

 portional length is in a 191, in i 192, in c 195, in b 200, in f/ 202, in h 

 208, in e 211, in/ 212, and in d 213. Evidently, therefore, this cha- 

 racter is too variable, and connected by too many intermediate grades, 

 to be of specific value. As to the second distinctive character, it is ab- 

 sent in a, b and h, faint in c, moderate in e and obvious in d, f, <j and /'. 



