OF THE MALAYAN REGION. 7 
not only has no male specimen of P. Polytes yet been found, but the female (Polytes) has 
never yet been found in localities to which the male (Pammon) does not extend. In this 
case, as in the last, distinct species, local forms, and dimorphic specimens have been con- 
founded under the common appellation of varieties. 
But, besides the true P. Polytes, there are several allied forms of females to be con- 
sidered, namely, P. Theseus, Cr., P. Melanides, De Haan, P. Elyros, G. R. G., and 
P. Romulus, L. The dark female figured by Cramer as P. Theseus seems to be the com- 
mon and perhaps the only form in Sumatra, whereas in Java, Borneo, and Timor, along 
with males quite identical with those of Sumatra, occur females of the Polytes form, 
although a single specimen of the true P. Theseus, Cr., taken at Lombock would seem to 
show that the two forms do occur together. In the allied species found in the Philippine 
Islands (P. Alphenor, Or., P. Ledebouria, Eschsch., 9 P. Elyros, G. R. G.) forms corre- 
sponding to these extremes occur along with a number of intermediate varieties, as shown 
by a fine series in the British Museum. We have here an indication of how dimorphism 
may be produced ; for let the extreme Philippine forms be better suited to their condi- 
tions of existence than the intermediate connecting links, and the latter will gradually 
die out, leaving two distinct forms of the same insect, each adapted to some special con- 
ditions. As these conditions are sure to vary in different districts, it will often happen, 
as in Sumatra and Java, that the one form will predominate in the one island, the other 
in the adjacent one. In the island of Borneo there seems to be a third form; for P. Mela- 
nides, De Haan, evidently belongs to this group, and has all the chief characteristics of 
P. Theseus, with a modified coloration of the hind wings. I now come to an insect 
which, if I am correct, offers one of the most interesting cases of variation yet adduced. 
Papilio Romulus, L., a butterfly found over a large part of India and Ceylon, and not 
uncommon in collections, has always been considered a true and independent species, 
and no suspicions have been expressed regarding it. But a male of this form does not, I 
believe, exist. I have examined the fine series in the British Museum, in the East India 
Company’s Museum, in the Hope Museum at Oxford, in Mr. Hewitson’s and several other 
private collections, and can find nothing but females; and for this common butterfly no 
male partner can be found except the equally common P. Pammon, a species already 
provided with two wives, and yet to whom we shall be forced, I believe, to assign a third. 
On carefully examining P. Romulus, I find that in all essential characters, —the form and 
texture of the wings, the length of the antennæ, the spotting of the head and thorax, and 
even the peculiar tints and shades with which it is ornamented,—it corresponds exactly 
with the other females of the Pammon group; and though, from the peculiar marking of 
the fore wings, it has at first sight a very different aspect, yet a closer examination shows 
that every one of its markings could be produced by slight and almost imperceptible 
modifications. of the various allied forms. I fully believe, therefore, that I shall be 
correct in placing P. Romulus as a third Indian form of the female P. Pammon, corre- 
sponding to P. Melanides, the third form of the Malayan P. Theseus. I may mention 
here that the females of this group have a superficial resemblance to the Polydorus 
group, as shown by P. Theseus having been considered to be the female of P. Antiphus, 
and by P. Romulus being arranged next to P. Hector. There is no close affinity between 
