r your paper on apterous lepidoptera (433/2.
Published by the West Kent Natural History, Microscopical and
Photographic Society, Greenwich, 1867. Mr. Weir's paper seems chiefly to
have interested Mr. Darwin as affording a good case of gradation in
the degree of degradation of the wings in various species.), which has
interested me exceedingly, and likewise for the very honourable mention
which you make of my name. It is almost a pity that your paper was
not published in some Journal in which it would have had a wider
distribution. It contained much that was new to me. I think the part
about the relation of the wings and spiracles and tracheae might have
been made a little clearer. Incidentally, you have done me a good
service by reminding me of the rudimentary spurs on the legs of the
partridge, for I am now writing on what I have called sexual selection.
I believe that I am not mistaken in thinking that you have attended much
to birds in confinement, as well as to insects. If you could call to
mind any facts bearing on this subject, with birds, insects, or any
animals--such as the selection by a female of any particular male--or
conversely of a particular female by a male, or on the rivalry between
males, or on the allurement of the females by the males, or any such
facts, I should be most grateful for the information, if you would have
the kindness to communicate it.

P.S.--I may give as instance of [this] class of facts, that Barrow
asserts that a male Emberiza (?) at the Cape has immensely long
tail-feathers during the breeding season (433/3. Barrow describes the
long tail feathers of Emberiza longicauda as enduring "but the season
of love." "An Account of Travels into the Interior of Southern Africa":
London, 1801, Volume I., page 244.); and that if these are cut off, he
has no chance of getting a wife. I have always felt an intense wish to
make analogous trials, but have never had an opportunity, and it is not
likely that you or any one would be willing to try so troublesome an
experiment. Colouring or staining the fine red breast of a bullfinch
with some innocuous matter into a dingy tint would be an analogous
case, and then putting him and ordinary males with a female. A
friend promised, but failed, to try a converse experiment with white
pigeons--viz., to stain their tails and wings with magenta or other
colours, and then observe what effect such a prodigious alteration would
have on their courtship. (433/4. Se