LEPIDOPTERA.— RHOPALOCERA. 335 
The sexes, although generally resembling each other, offer oc- 
casionally various distinctions, especially in colour, the males in 
such cases being almost invariably more gaily coloured: this is es- 
pecially the case in the Polyommati, Apaturee, and Lycenzx. In these 
the upper surface alone offers this distinction; the males of Man- 
cipium Cardamines have a bright orange spot at the tips of the fore 
wings. In Thecla Quercus, however (as proved by the dissections of 
Dr. Horsfield), the individuals which have a bright purple patch on 
the upper surface of the wings, and which have been by all other 
writers described as the males, are proved to be the females. The 
males of other species of the genus, as I have ascertained, are orna- 
mented with purple reflections. Some Argynnes have black longi- 
tudinal ribs on the fore wings of the males; and Mr. Haworth 
describes the female of Vanessa Atalanta as differing from the male 
in having a minute white dot in the central red fascia of the fore 
wings. Mr. Babington has noticed a difference in the colouring 
of the pupz of the two sexes of Pap. Machaon (Mag. Nat. Hist. 
No. 6.). Very few species of butterflies are gregarious in the larva 
state; those, however, of the Glanville fritillary live in societies 
not consisting of a hundred individuals in a kind of common tent 
which they construct upon the plantain. Several species of Vanessa 
are also social in this state, frequenting the nettle (V. Urticee and 
V. Io); as are also those of Papilio Archelaus, which live upon the 
orange trees in French Guiana (Lacordaire in Ann. Soc. Ent. de 
France, 1833, p. 385.). But a more perfect state of society is exhi- 
bited by a Mexican butterfly (Eucheira socialis Westw.), the cater- 
pillars of which construct a very strong parchment-like bag, in which 
they not only reside, but undergo their change to the pupa state. 
(Trans. Ent. Soe. vol.i. p. 38.) A similar occasional habit of con- 
gregating is exhibited by these insects in the perfect state. Such 
cannot, indeed, be said of the great numbers of white butterflies 
which may cccasionally be seen resting around the edges of ponds 
and other damp places, of which I have occasionally been witness ; 
but an immense swarm of Cynthia Cardui was observed in the 
Canton de Vaud in 1828, forming a column from ten to fifteen feet 
broad, traversing the couutry from north to south. Bonelli also 
observed a similar flight of the same species in the preceding year at 
the end of March. (Mém. Soc. Phys. de Généve.) De Loche also 
described a similar flight of C. Cardui, at the close of the last century 
