482 PROF. J. O. WESTWOOD ON INDIAN BUTTERFLIES. [Apr. 5, 



which agrees with Mr. G. R. Gray's " variety a " above mentioned ; 

 and figure 4 represents the underside of the hind wing of the typical 

 P. polliix. 



Plate XLV. fig. 2 represents a female insect from "India" in the 

 Hopeian Collection, measuring 4| inches in the expanse of the fore 

 wings, which agrees with the female P. pollu.v, except that the dis- 

 coidal fascia of the hind wings is reduced to a row of large hastate 

 marks beyond the middle of the wing, not reaching upwards to the 

 discoidal cell, more than half the basal portion of the wing thus being 

 of uniform rich brown colour, shghtly suffused beyond the middle 

 with fulvous scales — the fascia of hastate spots being but slightly 

 irrorated with dark scales, especially on the underside, and extending 

 across the wing to the anal margin. The hind wings of this female 

 specimen are of the rounded form of the ordinary females of P. 

 pollux. 



I have now to direct attention to another specimen from " India," 

 also in the Hopeian collection, figured in Plate XLV. fig. 1, which is 

 unquestionably a male, although it agrees so entirely in shape, colour, 

 and markings with the female represented in fig. 2 on the same 

 plate that it would be difficult to distinguish between them. 



Here, therefore, we have a clear proof that the opposite sexes of 

 the same species do not differ from each other, except in internal 

 sexual organization. 



Mr. Wood-Mason (Journal of the Asiatic Society of Bengal, vol. 

 xlix. part ii. 1880, p. 144, plates viii. and ix.) has lately described the 

 two last above-mentioned insects as the sexes of a new species, and 

 has applied to it the name P. dravidarum, of which he has given a 

 figure of the upperside alone of the male. The specimens described 

 by Mr. Wood-Mason were received from the Kadur district, Mysore, 

 and from Trevandrum. He considers my P. castor and P. pollux 

 as the two sexes of a distinct species, observing that in P. castor 

 " the sexes are, as regards colour and markings, as strongly differen- 

 tiated from one another as in any species with which I am acquainted ; 

 they also differ to some extent in form, the male having the fore wing 

 narrower, with the external margin obviously emarginate, and the 

 hind wing also narrower and produced, with the same margin more 

 deeply incised and lobed than in the female, both pairs of whose 

 wings in form more or less closely resemble those of both sexes in 

 the other two species," P. dravidarum and P. mahadesa from Bur- 

 mah, whilst " in P. dravidarum the sexes agree perfectly both in 

 form of the wings and markings, differing very slightly in colour 

 only ; so that but little sexual differentiation has here taken 

 place." 



With respect to the females of .ly P. pollux, Mr. Wood- Mason 

 states that specimens from Assam, Cherra Punji, and Silliet have 

 rounded hind wings, >hilst others from Silhet and Sikkim have 

 " the third branch of the median vein produced into a small tooth." 

 Of one of these he gives a figure, named P. castor $ , describing these 

 latter specimens as having more distinctly cream-coloured hind 

 wings than the rounded-winged ones. One of these light-coloured- 



