Frederick D. Welch — Forster's Milvago



41



rid of in order to leave the yellow pigment unaffected ? It is easier

to comprehend change of colour in the case of pigments than in the

structure of every feather in a bird’s plumage.


In floriculture one notes that individuals of the same flower exhibit

utterly dissimilar colouring in their blooms, probably absorbing from

the same soil different chemicals or varying quantities of the same

mineral colouring agent; but 1 should not expect the surface, say,

of a rich blue pansy to differ structurally from that of a golden-yellow

one ; indeed, we know well that in the case of these flowers the colouring

is not evidently pigmental or structural (in the accepted sense of the

term) since it is a fluid and permanent—perhaps representing pigment

in solution or infinitely small floating structures capable of intercepting

special light-rays ; it is not affected by the moulding of the outer

walls of the flower.


In insects blue pigment certainly does occur, unless I am greatly

mistaken, since we constantly see patches of dead blue in all shades

near to areas of black or brown structurally modified so as to exhibit

shot-blue colouring. Then when one transfers the scales of a butterfly’s

wing to gummed paper, thus reversing the scales, although one may

note prismatic effects upon the back of the scale which do not appear

on the front, the actual colour of the scale is retained, indicating the

presence of enclosed pigment.


The whole question of colour in nature is very interesting and

extremely complex ; one life is not long enough to enable one to get

to the bottom of a thousandth part of nature’s puzzles.



F() RSTE R ’S \ 11LYAGO


Bv Frederick D. Welch, M.R.C.S.


Birds which live long in captivity are of interest because they give

an idea of the length of life in the wild state, if fortunate enough to

escape destruction by enemies. It seems, therefore, worth recording

that of two specimens of birds of prey, Forster’s Milvago or Carrion

Hawk (Ihycter australis ) — a species native to the Falkland Islands —

which arrived in the London Zoological Gardens in July, 1886, both


G



