in the ground.

ECOLOGY AND HABITS. The skin of Frogs is usually smooth and free from
warts or horny excrescences. It is invested with a colorless epidermis,
which is shed from time to time as the creature grows; this splits
along the back and thighs, is worked over the head like the taking off
of a shirt, and usually eaten by the wearer. The deeper layers contain
much pigment, in cells which are more or less under muscular control,
enabling Frogs to change their hue to conform to the background.

Frogs are carnivorous, and in the season of activity are likely to be
very voracious. The terrestrial and arboreal forms feed mainly on
insects, worms, etc. The aquatic kinds also catch insects, but subsist
more on aquatic animals--worms, tadpoles, small fishes, and other
Frogs. These are seized and slowly swallowed, often, where before the
remainder, perhaps still alive, has been got within the mouth.

Extremes of cold or drought in climate must be avoided by Frogs.
Moisture of the skin is necessary to their health, and in very dry
places or seasons they survive only by going deeply under ground. Thus
some tropical species get through the "dry season." The frogs of
northern climates endure the winter by clustering about spring-holes
and other places where the water is comparatively warm and free of ice;
or else by hibernating in the mud. Terrestrial species bury themselves
for the winter in the loam, or burrow into the dry dust of rotting logs
and stumps. Their vitality is strong, and their power of regeneration
from partial congelation is very great.

Though most species live always in or near water, many spend the
greater part of their time away from it, and often in bushes or trees.
These, however, go to the water to breed; and as this function is
likely to demand attention early in the spring, it is then that these
animals make themselves most conspicuous by the incessantly uttered
croaking or rattling calls of the males, which are almost as varied as
the songs of the birds, and more ventriloquistic. These are wholly the
cries of the male Frogs, and cease when the mates have been found and
have spawned; and to assist in producing them many species have gular
air-sacs, which are connected with the vocal organs and furnish the
power required for the loud and insistent utterances. The great
ear-drums correlated with this vocal power are conspicuous in many
species.

The reproductive habits of Frogs are various. All of o