172 On Insects supposed to be distasteful to Birds. 
at once attack Cossus ligniperda, and although it is evidently 
not relished by them, my blackbird devoured one and thereby 
made his cage offensive for weeks. There must, I think, be 
something startling to birds in the violent black and white 
contrasts in the colouring of the moth which makes them 
hesitate to touch it. 
The idea that metallic colours are a protection to insects is 
a mistake; they are rather the reverse. A bird knows 
nothing of the nature of metal, but whatever is brilliant and 
shining he makes for at once, to see whether it is good to eat; 
all insectivorous birds, excepting, I think (but Mr. Poulton 
has my notes and can correct me if Iam wrong), the Wryneck, 
will eat the golden chrysalides of Vanessa urtice, and as for 
those bright metallic moths, the Plusiw, they are devoured 
immediately, as I found quite recently when I turned P. chry- 
sitis into my outside aviary and the Grey Wagtail seized 
and tore him to pieces directly he settled. 
As a rule it may be taken for granted that finches, omitting 
birds with such bunting-like habits as the type of Fringilla 
and the Waxbills, are very slightly insectivorous, and there- 
fore are very particular as to what they eat. Thus the 
Linnet group, including the Canary, will occasionally eat 
small green caterpillars, the Goldfinch group, including the 
Siskin, will eat aphides in abundance and probably also green 
caterpillars; the Chaffinch and Brambling, on the other 
hand, which more nearly resemble the Buntings in their mode 
of progression, are both ravenous insect-eaters, quite as much 
so as the Nonpareil, Indigo Finch, or Weaver-birds. 
Of truly insectivorous birds the Thrushes and their allies 
the Robins, including the Nightingale, are the least parti- 
cular, the Missel-Thrush and Blackbird even eating without 
hesitation the most hairy of hairy caterpillars, merely waiting 
to rub off the bristles before swallowing them; the Wryneck, 
on the other hand, is extremely dainty. 
It therefore appears to me that certain species of Lepido- 
ptera and of other insects may become abundant in certain 
years owing to the temporary scarcity of their particular 
enemies, but that never do they enjoy perfect immunity from 
destruction. 
Before closing these remarks I wish to disabuse entomolo- 
gists of the notion that the spider-like appearance of the larva 
of Stauropus is intended as a protection against birds. If 
there is one thing that all insectivorous birds love it is a 
spider ; unless he is at the point of death the sight of a spider 
will rouse even a sick bird to activity ; the shout of pleasure 
which a Bulbul gives when you offer him a spider is alone 
