302 STATES OF INSECTS. (Jmago.) 
our rarest and most beautiful butterflies, has only a single 
black spot in the disk of its fulgid wings; while in the 
other sex, the primary pair have nine, and the secondary 
are black, with a transverse orange fascia near the pos- 
terior margin. But the most remarkable difference in 
this respect observable in the insects of the order in 
question, takes place ina tribe, of which only one species 
is certainly known to inhabit Britain—I mean the Pa- 
piliones Equites of Linné: what he has called his Tro- 
jani and Achivi in some instances have proved only dif- 
ferent sexes of the same species. Mr. MacLeay’s rich 
cabinet affords a singular instance confirming this asser- 
tion ;—a specimen of a Papilio is divided longitudinally, 
the right hand side being male, and the left hand female. 
The former belongs to P. Polycaon, a Grecian, the lat- 
ter to P. Laodocus, a Trojan. An instance of two Gre- 
cians thus united is recorded in the Encyclopédie Métho- 
dique, as exhibited in a specimen preserved in the Mu- 
seum of Natural History at Paris; which on the right 
hand side is P. Ulysses, on the left P. Diomedes*. 
In the Neuroptera, the Libellulide are remarkable for 
the differences of colour in the sexes. In the common 
Libellula depressa, which you may see hawking over 
every pool, the abdomen of the male is usually slate-co- 
lour, while that of his partner is yellow, but with darker 
side-spots. Reaumur, however, noticed some males 
that were of the same colour with the females >. Schelver 
observed, when he put the skins of Libellula depressa 
into water, that the colours common to both sexes were 
in the substance of the skin, and remained fixed ; while 
those that were peculiar to one could be taken off with 
* ix. 65. 2. 110. > vi. 423. 
