This beautiful genus is easily recognized by its peculiar aspect, as
well as by the more precise characters which it affords. The anterior
wings are long, narrow, and entire, and the hinder pair often recede
considerably from the abdomen, which is long and slender. The breadth
of the insect, therefore, when flying, always greatly exceeds its
length. No lepidopterous insect is ever entirely without scales, but
in a section of this group, they are so few and minute as to leave
the wings perfectly transparent. The palpi rise obviously above the
head; the second joint is greatly longer than the first, and has a
long tuft of hair near the apex, the terminal one is also a good deal
produced. The antennæ are, at least, double the length of the head and
thorax, and thicken gradually at the extremity. The anterior tarsus is
considerably dilated and slightly dentated; claws simple. Such of the
caterpillars as have been described, differ remarkably from each other,
and some of them seem to have no analogy with those of the neighbouring
groups. This discrepancy, in connexion with some others in the perfect
insects, has already led to the separation of certain groups from
_Heliconia_ as it was formerly constituted. The larva of _H. Euterpe_
is robust and depressed, with a series of long fleshy lobes on each
side; that of _H. Calliope_ short and cylindrical, clothed with slender
spines and tufts of hair: these species form the genus _Nerias_,
although they are too dissimilar to be associated with propriety.
Others are smooth (_H. Psidii_), and some are covered with very long
white hairs (_H. Ricini_). In these circumstances, it is not likely
that a natural arrangement of this pretty group will be effected until
we become better acquainted with the caterpillars, very few of which
have hitherto been examined. Chrysalis invariably suspended by the tail
only.
These insects, as has been already mentioned, are confined to America
and the West India Islands, the larva subsisting on the different kinds
of _Passifloræ_, a beautiful tribe of plants well known to be likewise
peculiar to the new world. They seem to be represented in India, as Dr.
Horsfield remarks, by the genera _Euplœa_ and _Idea_.
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