THE GENUS OPORABIA. 249 



distinct on costa. (3rd) The black mark at the bifurcation of 2nd and 

 3rd nervures prominent. (4th) Elbowed line (when distinct enough 

 to be traceable) much less dentated than in the common species, and 

 forming almost a right angle on the 1st nervure (sub-costal). (5th) 

 Female similar to male, not smaller and stronger marked, as in 

 nebulata. (6th) The larva confined to birch, and entirely green, 

 without the red markings of nebulata. Nos. 1, 2 and 3 of the 

 above I dismiss as absolutely valueless for purposes of differentia- 

 tion. No 4 is interesting, because associating this form rather 

 with fdif/ramiiiaria than with normal nebulata ; yet I have seen 

 specimens of the latter (very occasionally) with the elbowed line 

 considerably angulated. The angulation of this line, the silky 

 aspect of the insect, the equahty in the size of the sexes, and 

 the specified food-plant (birch) are probably the principal causes 

 of the dire confusion that has arisen between this autwnnata and the 

 autumnaria of Weaver and Doubleday, etc. — a confusion of which 

 I shall speak further presently. Regarding Guenee's 6th distinction — 

 that of the larva — he himself admits that the two species are 

 extremely close ; it seems to me not only useless, but positively mis- 

 leading, to appeal to the absence of red markings ; even our Epping 

 Forest specimens, on oak, etc., are often devoid of these ; while 

 Schoyen states (Arch. Math. o</ Natiirvid., vol. iii.) that in Scandinavia 

 (where, be it remarked, the usual food-plant is birch) they have never 

 been found red- or brown-spotted, but always uniform green, with 

 yellowish lateral lines and lighter beneath. As I have not seen any 

 Scandinavian examples, of course I cannot say positively that the 

 species may not be one of the jili(/rainmaria group ; the mention of 

 yellowish lateral lines in the larva, together with Aurivillius' descrip- 

 tion of the (? genitalia, may perhaps point in that direction. 



Whether this autwnnata of Guenee's be a variety or a species, it 

 will probably require re-naming ; its erection only dates from 1857, 

 and it is in collision both with autumnata, Bkh., and with autumnaria 

 (Dbld.), Weaver {Zool., 1852). 



(To he continued). 



On a collection of Spring Rhopalocera made in the Riviera, with 

 some considerations concerning the hybernating stage of certain 



butterflies. 



By J. W. TUTT, F.E.S. 



The stage in which some of our butterflies hybernate has long 

 been a puzzle to me, and I have long suspected that a definite 

 knowledge of the habits of certain species which have been but little 

 observed in Britain, can only be cleared up by a close study of the 

 habits of the same species on the Mediterranean littoral, which appears 

 to be the region in which they exist under the most favourable 

 conditions. Unfortunately, the notes scattered throughout the 

 magazines do not as a rule afford much aid, and may often, 

 indeed, be positively misleading. When, therefore, I knew that Dr. 

 Chapman would spend the early spring in the Riviera, I felt quite 

 satisfied that some reliable information as to the habits of certain 



