OF THE MALAYAN REGION. 57 



is a male insect known which can be mated with it, except those of the Orme iius-f ovm. 

 (which always occur in the same places), may, in conjunction with tlie observation already 

 s^iven of the companionship of the two forms, be taken to prove that this is really a case 

 of polymorphism. I believe also it will be found that these extreme departures from 

 the typical form of a species are connected with mimetic resemblances and the safety of 

 the individuals. We have already seen that the extreme forms of P. Memnon 2 and 

 P. Pammon 2 respectively resemble other species which from their habits and abun- 

 dance seem to have some peculiar immunity from danger. In this case also there is a 

 resemblance to quite a different family of butterflies, the Morphidtc. In form, colora- 

 tion, and general appearance. these pale-coloured Papilios resemble species of the genus 

 Dnisilla ; and the same genus is also imitated by other butterflies — one of these, Mela' 

 nitis Agondas ? , having been actually confounded with Drusilla bioculuta as the same 

 species, so great is the resemblance. This fact of species of several genera imitating 

 the Drusillas wovxld indicate that they have some special immunities which make it 

 advantageous to other insects to be mistaken for them ; and their habits confirm this 

 opinion. They have all a very similar style of dress, and fly very slowly, low down in 

 damp woods, often settling on the ground or on rotten Avood ; and they are exceedingly 

 abundant in individuals. Now these are the general characteristics of all groups which 

 are the sulijects of imitation ; and we may therefore jn-esume, when we see forms depart- 

 ing widely from the general appearance of tlieir close relations, and resembling closely 

 other groups with which they haA'e no affinity, that what we must call accidental vari- 

 ations have been accumulated and rendered definite by natural selection for the protec- 

 tion and benefit of those forms. 



73. Papilio Tydetjs, Pelder. Tab. IV. figs. 3 ( j ), 2 ( ? ). 

 P. Tijdeus, Feld. Lep. Fragm. p. 52 (d). 



Female. — Upper side dusky brown ; fore wings with the central portion below the 

 cell nearly white ; hind wings with the basal two-thirds white, with an irregular and 

 obtusely dentated margin, and edged with ochre-yellow ; the rest black, with a submargi- 

 nal row of seven broad yellowish lunuies, and above those nearest the anal angle three 

 irregular blue patches. 



Under side nearly as above ; the white space on the upper wings is more extensive 

 and better defined ; the marginal lunuies are dilated so as to form a crenellated band, and 

 the blue marks are increased to six or seven in number. Head and thorax dusky; 

 abdomen yellowish. 



Hab. Batchian, Morty Island {Wall.). 



Remark. — The female, which seems to be of only one form in this species, is especially 

 interesting as being allied to the pale-yellow form of P, Ormemis and P. Pandion. 



74. Papilio Adeastus, n. s. Tab. lY. fig. 1 ( $). 



Hale. — Upper side, like P. Onneuus d ; but has the band of the hind wings narrower, 

 not crossing the cell, and more pointed towards the anal angle. 



VOL. XXV. I 



