represented in the males only by thin streaks ; and in Pieris it is the
females which are ornamented with black spots on the fore-wings, and
these are only partially present in the males. Now the males of many
butterflies are known to support the females during their marriage
flight; but in the species just named it is the females which support
the males; so that the part which the two sexes play is reversed, as is
their relative beauty. Throughout the animal kingdom the males commonly
take the more active share in wooing, and their beauty seems to have
been increased by the females having accepted the more attractive
individuals; but with these butterflies, the females take the more
active part in the final marriage ceremony, so that we may suppose that
they likewise do so in the wooing; and in this case we can understand
how it is that they have been rendered the more beautiful. Mr. Meldola,
from whom the foregoing statements have been taken, says in conclusion:
Though I am not convinced of the action of sexual selection in
producing the colours of insects, it cannot be denied that these facts
are strikingly corroborative of Mr. Darwin s views. (23. Nature,
April 27, 1871, p. 508. Mr. Meldola quotes Donzel, in Soc. Ent. de
France, 1837, p. 77, on the flight of butterflies whilst pairing. See
also Mr. G. Fraser, in Nature, April 20, 1871, p. 489, on the sexual
differences of several British butterflies.)
As sexual selection primarily depends on variability, a few words must
be added on this subject. In respect to colour there is no difficulty,
for any number of highly variable Lepidoptera could be named. One good
instance will suffice. Mr. Bates shewed me a whole series of specimens
of Papilio sesostris and P. childrenae; in the latter the males varied
much in the extent of the beautifully enamelled green patch on the
fore-wings, and in the size of the white mark, and of the splendid
crimson stripe on the hind-wings; so that there was a great contrast
amongst the males between the most and the least gaudy. The male of
Papilio sesostris is much less beautiful than of P. childrenae; and it
likewise varies a little in the size of the green patch on the
fore-wings, and in the occasional appearance of the small crimson
stripe on the hind-wings, borrowed, as it would seem, from its own
female; for the females of this and of many other species in the Aeneas
group possess this crimson stripe. Hence between the brightest
specimens of P. sesostris and the dullest of P. childrenae, there was
but a small interval; and it was evident that as far as mere
variability is concerned, there would be no difficulty in permanently
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