56 ON THE CLASSIFICATION OP BIRDS. 
themselves round the hase of the lower mandible, as if 
to defend the mouth in all directions ; but we do not 
at this moment remember any other birds with a similar 
formation. "J'hese appendages being found only in 
such birds as feed 
upon insects, and 
chieflyin thosewhich 
catch their prey on 
the wing, leaves us in 
no doubt as to their 
specific use. Among 
the swallows, indeed, 
these bristles cannot be found, because the insects they 
live upon, being very small, are swallowed without any 
difficulty, and are incapable of making any struggles • 
but the case is far different with those captured by 
the night-jars, whose chief sustenance is derived from 
coleopterous insects which fly in the evening, and whose 
hard legs and bifurcated claws might inflict much 
injury in their struggles to escape. Now, the bristles 
we are describing, are more developed in this tribe of 
birds than in any of those which feed upon the wing ; 
and they obviously answer two purposes, — they protect 
the angles of the mouth from any injury, while at the 
■same time they confine the struggles of the captive 
insect. In the genuine flycatchers, these bristles are 
rather less developed ; although in some few, as in the 
genus Megahphus*, they are very long : but then, on the 
other hand, the Ji^uscicupineB never, or very rarely feed 
upon coleopterous insects, but seem to confine them- 
selves to those whose bodies are soft ; yet, as the wings 
of these latter are often large, the bristles are necessary 
to confine their fluttering. It is rather singular that 
the woodpeckers, which feed upon coleopterous insects, 
as well as soft larva, are destitute of these bristles; but 
we may observe that the feathers round the mouth are 
remarkably thick and compact, and that the nostrils are 
Megaluphus regius, Braziliau Birds, pi. Si, 52, 
