The Descent of Man

mies; nevertheless, as the hind-wings are 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.