ty to modifying causes is not
imaginary may, I think, be drawn from the consideration, that while the
Lepidoptera as a whole are of all insects the least essentially varied
in form, structure, or habits, yet in the number of their specific forms
they are not much inferior to those orders which range over a much wider
field of nature, and exhibit more deeply seated structural
modifications. The Lepidoptera are all vegetable-feeders in their
larva-state, and suckers of juices or other liquids in their perfect
form. In their most widely separated groups they differ but little from
a common type, and offer comparatively unimportant modifications of
structure or of habits. The Coleoptera, the Diptera, or the Hymenoptera,
on the other hand, present far greater and more essential variations. In
either of these orders we have both vegetable and animal-feeders,
aquatic, and terrestrial, and parasitic groups. Whole families are
devoted to special departments in the economy of nature. Seeds, fruits,
bones, carcases, excrement, bark, have each their special and dependent
insect tribes from among them; whereas the Lepidoptera are, with but few
exceptions, confined to the one function of devouring the foliage of
living vegetation. We might therefore anticipate that their
species--population would be only equal to that of sections of the other
orders having a similar uniform mode of existence; and the fact that
their numbers are at all comparable with those of entire orders, so much
more varied in organization and habits, is, I think, a proof that they
are in general highly susceptible of specific modification.

_Question of the rank of the Papilionidae._

The Papilionidae are a family of diurnal Lepidoptera which have hitherto,
by almost universal consent, held the first rank in the order; and
though this position has recently been denied them, I cannot altogether
acquiesce in the reasoning by which it has been proposed to degrade them
to a lower rank. In Mr. Bates's most excellent paper on the Heliconidae,
(published in the Transactions of the Linnaean Society, vol. xxiii., p.
495) he claims for that family the highest position, chiefly because of
the imperfect structure of the fore legs, which is there carried to an
extreme degree of abortion, and thus removes them further than any other
family from the Hesperidae and Heterocera, which all have perfect legs.
Now it is a question whether any amount of difference which is exhibited