then fully exposed to view, their bright colours must generally have
been acquired at some little risk. But the following fact shews how
cautious we ought to be in drawing conclusions on this head. The common
Yellow Under-wings (Triphaena) often fly about during the day or early
evening, and are then conspicuous from the colour of their hind-wings.
It would naturally be thought that this would be a source of danger;
but Mr. J. Jenner Weir believes that it actually serves them as a means
of escape, for birds strike at these brightly coloured and fragile
surfaces, instead of at the body. For instance, Mr. Weir turned into
his aviary a vigorous specimen of Triphaena pronuba, which was
instantly pursued by a robin; but the bird s attention being caught by
the coloured wings, the moth was not captured until after about fifty
attempts, and small portions of the wings were repeatedly broken off.
He tried the same experiment, in the open air, with a swallow and T.
fimbria; but the large size of this moth probably interfered with its
capture. (12. See also, on this subject, Mr. Weir s paper in
Transactions, Entomological Society, 1869, p. 23.) We are thus
reminded of a statement made by Mr. Wallace (13. Westminster Review,
July 1867, p. 16.), namely, that in the Brazilian forests and Malayan
islands, many common and highly-decorated butterflies are weak flyers,
though furnished with a broad expanse of wing; and they are often
captured with pierced and broken wings, as if they had been seized by
birds, from which they had escaped: if the wings had been much smaller
in proportion to the body, it seems probable that the insect would more
frequently have been struck or pierced in a vital part, and thus the
increased expanse of the wings may have been indirectly beneficial.
DISPLAY.
The bright colours of many butterflies and of some moths are specially
arranged for display, so that they may be readily seen. During the
night colours are not visible, and there can be no doubt that the
nocturnal moths, taken as a body, are much less gaily decorated than
butterflies, all of which are diurnal in their habits. But the moths of
certain families, such as the Zygaenidae, several Sphingidae,
Uraniidae, some Arctiidae and Saturniidae, fly about during the day or
early evening, and many of these are extremely beautiful, being far
brighter coloured than the strictly nocturnal kinds. A few exceptional
cases, however, of bright-coloured nocturnal species have been
recorded. (14. For instance, Lithosia; but Prof. Westwood ( Modern
343