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



a female specimen (of which sex many more specimens have been 

 obtained) having the upperside of the wings dark brown, with a 

 small whitish dot at the extremity of the discoidal cell of the fore 

 wings, and a row of small submarginal white spots (of different sizes) 

 parallel to the onter margin of the fore wing, which is marked with 

 slight marginal white incisions. The hind wings on the upperside 

 have a broad fascia of dirty greenish-white colour, strongly irrorated 

 with blackish scales, extending all across the middle of the wing and 

 into the discoidal cell, and divided by the longitudinal veins into 

 seven longitudinal patches ; the outer margin of this fascia is scalloped, 

 and is followed by a submarginal row of seven large white hmules, 

 the one next the anal angle being divided in the middle, and with 

 very slight marginal white incisures between the veins. On the 

 underside the pale-coloured portion of the hind wings (Plate XLIV. 

 fig. 4) extends much further towards the base of the wings, and is 

 also partially seen on the inner portion of the fore wings ; the sub- 

 marginal lunules are also larger. Various specimens of this female 

 varied from 4^ to 5^ inches in expanse. It is to be further noticed 

 that the hind wings are rounded in form, with the hind margins 

 slightly scalloped. 



From tlie preceding observations it will be seen that, in addition 

 to the different dimensions, P. castor is distinguished by the large, 

 nearly white 4-partite spot between the outer angle and the disk of 

 the hind wings, which are elongate-ovate in form ; whilst P. pollux 

 has rounded hind wings, nearly the whole of the disk of which bears 

 a broad 7-partite band of strongly irrorated greenish-white colour, 

 separated by the veins, and gradually shaded off into the dark base 

 of the wings, and with a submarginal row of whitish lunules. 



In the extensive genus Papilio there is great diversity in the ex- 

 tent of difference between the two sexes of the same species. Thus, 

 whilst in some (P. machaon, P. podalirius, &c.) it is almost impossible, 

 without microscopical examination, to distinguish the male from the 

 female, other species differ so greatly in size, shape, colour, and 

 markings as to lead to the opposite sexes being easily mistaken (as, 

 indeed, in many instances has been the case) for distinct species. 

 The decided determination of this question is, of course, only to be 

 obtained by an examination of the insects in nature, either by ob- 

 serving their actual sexual connexion, or by rearing the two sexes 

 from the same batch of eggs. Beyond this, of course, the assertion 

 of the sexual connexion between two dissimilar insects must of course 

 be conjectural ; and conjecture has been at work with the two insects 

 under consideration. 



The late Mr. E. Doubleday introduced these insects as two distinct 

 species in his portion of the ' Genera of Diurnal Lepidoptera,' P. 

 castor being his 72nd species (p. 12), placed between P. erithonius, 

 Cramer, and P. phestus, Bdv. & Guerin, ' Voy. Coquille, Ins.' pi. 14. 

 f. 2 (to which latter it bears considerable resemblance in form) ; 

 whilst P. pollux is his 264th species, placed between P. dissimilis, 

 Linn. (P. panope, Linn., $), and P. palephales,Viest\v. 'Arc. Ent.' 

 t. 79. f. 1,2, from Manilla. 



