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 /'.
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