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limbs ; the whole form being slender, and the muzzle pointed. Its general colour is
greyish brown, with dark spots ; the temporal spot being dark and distinct, with a
light line running from its extremity to the snout, while the hind-limbs are
regularly barred, and the under-parts unspotted. Two other European species, the




me (R. iberica) from Spain and Portugal, and the other (R. latastei) from the
neighbourhood of Milan, differ by the spotted lower surface of the body. Even the
tadpoles of the whole of these more or less nearly allied species present differences
by which they can be distinguished from one another.

The common frog, whose habits may be taken as typical of the allied members
of the genus, is found in most parts of Europe, where there is a sufficiency of
moisture and shelter for its existence ; the presence of water being essential during
the breeding-season. All are probably familiar with the manner in which a frog
swallows air ; but it is perhaps less generally known that if the mouth of one of
these creatures be kept forcibly open, death must inevitably ensue, owing to the
impossibility of breathing while in this state. The croaking of the frog is
principally uttered during the breeding-season ; and when large numbers of these



268 FROGS AND TOADS.

Amphibians are collected in a pond together, the volume of sound produced is con-
siderable, and can be heard from long distances, although it is nothing compared to
that of the bull-frog and many tropical species. Frogs subsist entirely on sluj
snails, insects, etc., swallowing large beetles whole, and devouring several at a met
The frog captures its prey by suddenly throwing forwards the tip of its tongut
which is invested with a viscid secretion, upon the insect or slug, and then
quickly withdrawing it to its normal inverted position. So rapid is the whoh
movement, that it requires a sharp eye to detect it ; the insect seeming to disappear
as if by magic. " Frogs retire," writes Bell, " on the approach of winter to their
hibernating retreats, where they pass the dreary season in a state of absolute
torpidity. This is generally in the mud at the bottom of the water, where they
are not only preserved, though at low degree, but also secured from external
injury. Here they congregate in multitudes, embracing each other so closely as to
appear almost as one continuous mass. On the return of spring they separate from
each other, emerge from their places of retirement, and recommence their active
life by exercising the important function of reproducing their species." During
the breeding-season a warty protuberance is developed on the thumb of the male
to assist in holding the female ; and in some foreign species the whole fore-arm
becomes enlarged at this time. The spawn is deposited at the bottom of the
water, but soon rises to the surface in the well-known glairy masses ; and in due
season the tadpoles make their appearance. During the tadpole stage frogs are
devoured in large numbers by newts and the smaller fishes ; while in the adult
condition numbers fall a prey to the weasel and pole-cat, the heron and other
wading birds and the common snake, whose food is almost entirely composed of
them. Although the common frog is to a large extent aquatic, it is much less so
than the edible species, which inhabits indiscriminately running or still waters, the
borders of rivers, rivulets, or streams, lakes or ponds, salt or fresh marshes, or even
ditches and pools of water. Owing to the presence of the external sacs, the croak-
ing of the male is louder than in the common frog. . Both species, like all the more
typical representatives of the genus, progress on land by means of leaps ; while ii
water they swim with the hind-limbs alone.

Compared to the bull-frog (R. catesibyana), of Eastern



America, represented in the figure on p. 259, the European frogs ai
mere dwarfs ; but the largest species of all is Guppy's frog (R. guppyi), froi
the Solomon Islands, in which the length of the head and body is upwards of
inches. The bull-frog is one of those species in which the tips of the toes
pointed, and it is especially characterised by the web extending to the tip of tl
fourth toe of the hind-foot, the large size of the aperture of the ear, and tl
relative length of the hind-leg ; the two latter characters distinguishing it froi
Montezurna's frog (R. montezumce), of Mexico. The body has no lateral glanduh
fold ; and the vocal sacs of the males are internal. In colour the bull-frog is
or olive above, with darker marblings ; the under-parts being cither uniform]
coloured, or marbled with brown. In length it measures from 7 to 7i inclu
exclusive <>!' (lie legs. More abundant in the southern than in the northci
portion of its habitat, the bull-frog is generally met with in rivers and strcai
well shaded with trees or bushes, where it may be seen in numbers basking in



TYPICAL FROGS.



269



le midday sun. Its croaking is said to be louder than that of any other species,
ind can be heard for a distance of several miles. In the Southern States of
unerica, although most intense during the spring and summer, the croaking
continued throughout, the year ; but in the north it is confined to the spring
summer, being especially loud during the breeding-season. It is a remarkable
that in Canada, at least, the bull-frog passes its first winter in the larval
mdition, and takes two years to attain its full growth.

It may be mentioned that the small Indian frogs forming the
genus Oxyglossus differ from the members of the preceding genus by
le absence of any notch in the tongue, and the want of vomerine teeth. They
specially interesting on account of being represented by fossil species in the



Oxyglossus.





Flying Frogs.



JAVAN FLYING FROG ( liat. Size).

iene rocks of Bombay. Fossil frogs belonging to the typical genus Rana occur
lower Miocene rocks of Europe.

" One of the most curious and interesting reptiles which I met
with in Borneo," writes Mr. Wallace, " was a large tree-frog, which
was brought me by one of the Chinese workmen. He assured me that he had seen
it come down, in a slanting direction, from a high tree, as if it flew. On examin-
ing it, I found the toes very long, and fully webbed to their very extremity, so
that when expanded they offered a surface much larger than that of the body.
The fore-legs were also bordered by a membrane, and the body was capable of con-
siderable inflation. The back and limbs were of a very deep shining green colour,
the under surface and inner toes yellow, while the webs were black, rayed with
yellow. The body was about 4 inches long, while the webs of each hind-foot, when
fully expanded, covered a surface of 4 square inches, and the webs of all the feet
together a.bout 12 square inches. As the extremities of the toes have dilated discs






270



FROGS AND TOADS.



Madagascar.



for adhesion, showing the creature to be a tree-frog, it is difficult to imagine that
this immense membrane of the toes can be for the purpose of swimming only, and
the account of the Chinaman, that it flew down from the tree, becomes more
credible." The species referred to is the Bornean flying frog (Rhacophorv*
pardalis), a member of a large genus, of which another representative (R. rein-
wardti), is shown in the illustration on p. 269. Of the forty-two species of
the genus, thirty occur in South and East Asia, and the remaining twelve in
While allied in most respects to the water-frogs, they all differ by the

presence of a small ad-
ditional bone between
the terminal and penul-
timate joints of the toes,
and likewise by the
penultimate joints being
distinctly marked exter-
nally as a kind of ridge ;
while they are further
mostly characterised by
the webbing of the toes
of the fore-feet, although
the degree to which this
is carried is variable.
The tips of the toes are
always expanded into
round discs, and very
generally their terminal
joints are forked. The
males are provided with
one or two internal vocal
sacs. In habits these
frogs are strictly
arboreal; their bright
green coloration har-
monising with the
leaves among whicl

they dwell. The larvae are remarkable for the possession of an adhesive di.-
behind the mouth on the under surface ; while the muzzle is prolonged into
proboscis, and the single breathing-pore is situated on the right side of the body,
nearer to the tail than to the muzzle. Writing of the habits of one of tin-
Cingalese members of the genus (formerly separated as Polypedates), in which
the front toes are only half-webbed, Emerson Tennent observes that it "possesses
in a high degree, the faculty of changing its hues; one as green as a leaf to-day
will be found grey and spotted like the back to-morrow. One of these beautiful
little creatures, which had seated itself on the gilt pillar of a lamp on my dinner-
table, became in a few minutes scarcely distinguishable in colour from the ormolu
ornament to which it clunir."




VARIABLE TUBE-FROGS (liat. size).



SO LID- CHESTED TREE-FROGS. 271

THE SOLID-CHESTED TKEE-FROGS.

Family DENVROBATID+E

As we have already seen to be the case with the snakes, two totally distinct
families of frogs have taken to an arboreal life, and have thus become so like one
another that we have to depend on anatomical differences for their distinction.
In the present family, while the structure of the bones of the chest is of the same
solid structure as obtains in the typical frogs, and the extremities of the transverse
processes of the sacral vertebra are not expanded, an important difference presents
itself in the absence of teeth in the upper jaw and on the palate. The toes of both
feet are quite free from webs, and have their tips expanded into rounded discs.
These frogs are represented by two genera, one of which (Mantella) is confined to
Madagascar, and is distinguished by the tip of the tongue being notched ; while in
Dendrobates of Tropical America the tongue is entire. The American genus is
represented by seven species, among which the variable tree-frog (Dendrobates
tinctorius) is selected for illustration. This pretty little frog, which measures
barely an inch and a half in length, is widely distributed in Tropical America, and
is remarkable for its variability in colour ; some examples being uniformly black,
others grey above and black on the sides and beneath, and others grey with large
black blotches. This, however, is by no means the limit of variation, since some
examples are black above, with two or three longitudinal white or pink stripes, the
under-parts being grey with black spots ; while in other cases, the ground-colour is
black, with white spots and streaks above, and spots or marblings of the same
beneath. From the small size of the discs on its feet, which do not admit of its
clinging to upright stems, this frog seems to be less arboreal than some of its
allies ; and it is generally found among fallen leaves on the ground in forests.
Like its kindred, it displays remarkable care and attention to its young. The
jcretion from its skin is employed by the Indians as an arrow-poison.

THE NARROW-MOUTHED FROGS.
Family ENGYSTOMATID^S.

An important family of the suborder is that of the narrow-mouthed frogs,
represented by more than a score of genera, distributed over Africa, Madagascar,
India and the adjacent countries, Southern China, Papua, and America. While
agreeing with the members of the preceding family in the absence of teeth in the
upper jaw, these frogs are distinguished by the broad expansion of the extremities
of the transverse processes of the sacral vertebra. The vertebrae are similar in
conformation to those of the typical frogs, and there is the same absence of ribs.
There is, however, considerable variation in regard to the bones of the chest,
several of the genera lacking the transverse bars commonly known as precoracoids ;
and the terminal joints of the toes may be either simple or T-shaped. Although
there are no arboreal forms, the family comprises terrestrial, aquatic, and burrowing
representatives ; the last having either the front or hind-limbs specially strength-



272



FROGS AND TOADS.



ened and furnished with horny sheaths. In some of the genera, and especially the
one of winch a representative is here figured, the mouth is extremely narrow ;
and although it is convenient to take this character as the basis of the name of tin-
family, it must not be considered that it is applicable to all its members. Th<'*<-
narrow-mouthed forms feed exclusively or mainly on ants and termites, and thus
exhibit a modification of structure approximating to that characteristic of ant-
eating mammals. More than half the members of the family are nocturnal, and
may be recognised by the vertical pupil of the eye.

Short-Headed The exceeding plumpness of the body serves not only to dis-

fross. tinguish the short-headed frogs (Breviceps) from all their allies, but

also makes them some of the most peculiar of their class. Indeed, when the body




EAST AFRICAN SHORT-HEADED FROGS (nat. size).

is puffed out to its fullest extent, they more resemble indiarubber balls than frogs.
The genus belongs to a group in which the so-called precoracoid bones are present
and the metacoracoids much dilated ; and they are specially distinguished by the
horizontal portion of the pupil and the absence of teeth on the palate. Thre
species are known, all of which are African, the one here figured (B. mossambicus)
inhabiting the eastern districts. Generally having a perfectly smooth skin, this
frog is of a brown or blackish hue on the upper-parts, with a dark oblique streak
below the eye. The narrow mouth and long tongue of this curious frog indicate
that its food consists of white ants.

A frog (RltiiKK/n-ma darwini) belonging to the present family,
and inhabiting Chili, alone represents a genus remarkable for the



NARRO W-MO UTHED GROUP.



273



throat-sac of the males being enlarged and modified so as to form an extensive
chamber on the under surface of the body in which the eggs and tadpoles undergo
their development. This chamber is entered by two apertures situated on the
floor of the mouth on each side of the tongue ; and when the eggs, generally from
eleven to fifteen in number, are laid by the female, they are taken and swallowed
by her consort, who passes them into his pouch. When the tadpoles are sufficiently
developed, they enter the world by escaping through the parental mouth. It
appears that at no stage of their existence do the tadpoles possess external gills.
A ' I

THE SHARP-NOSED FROG.

Family CERATOBATRACHIDAt:.

Omitting detailed mention of the small and unimportant family of the
Discophidce, characterised by the presence of teeth in the upper jaw, and the
expansion of the extremities of the transverse processes of the sacral vertebra, our
last representative of the first suborder is the sharp-nosed frog (Ceratobatrachus
gmntheri), of the Solomon Islands, which constitutes a family by itself. The
essential characteristics of the family are the presence of teeth in both the upper
and lower jaws (a feature found elsewhere only in two families of the next
suborder), coupled with the absence of expansion of the extremities of the sacral
vertebrae This frog has a very large triangular head, ornamented with prominent
ridges, and terminating in front in a pointed flap of skin; similar flaps occupying
the eyelids, and the mouth having an enormous capacity. In the eye the pupil is
horizontal ; and teeth are present on the vomers. The hind-limbs are rather short ;
and all the toes have simple terminations, and are devoid of webs. In colour this
curious frog is very variable. Although very little is known as to its habits, it
appears to be abundant in the Solomon Islands ; and it is remarkable for laying
very large eggs, from which the young emerge nearly fully-developed.

THE SOUTHERN FROGS.
Family LEPTODAGTYLID^.

In the greater part of South America and the whole of Australia the typical
frogs are replaced by a family which, for want of a better name, we may call the
southern frogs. These, together with seven other families, differ essentially from
the forms hitherto considered, in regard to the conformation of the bones of the
chest, and thus collectively constitute a second suborder, known as the Arcifera.
It will be remembered that in the preceding suborder the two metacoracoid bones
are connected together by a single cartilage joining their free edges ; in the present
group each metacoracoid terminates in a large cartilage, in such a manner that one
cartilage overlaps its fellow of the opposite side. The southern frogs resemble the
typical frogs in having the upper jaw alone toothed, and in the transverse processes
of the sacral vertebra being cylindrical or but slightly expanded, while they also
agree in the characters of the vertebrae and the absence of ribs. It is thus evident

VOL. v. 1 8



274



FROGS AND TOADS.



that the two groups form parallel or representative series ; but it must always be
remembered that it is only an assumption that the conformation of the bones of the
chest is the character of primary import ; and that it is quite possible that there
may have been parallelism in this case also, in which event the present family
would have to be placed next the true frogs. The present family is confined to the
countries mentioned above, and is represented by twenty-five genera and some one
hundred and eighty species. While most of the American forms have the pupil of
the eye vertical, this condition occurs but rarely in those from Australia.







SOLOMON ISLAM) SHARP-NOSED KROG (nat. size).

Among the best known representatives of the family arc t
horned frogs, or horned toads (Ceratoplirys), remarkable alike fo
their large size and brilliant coloration, as well as for the enormous dimensions
their mouths and their fierce and carnivorous habits. Represented by about h
a score of species from Tropical and South America, they belong to a group cha
terised by the more or less marked union of the outer metatarsals, the absence of
bony style to the breast-bone, and the webbing of the hind-toes ; while, as a genus,
they are distinguished by the horizontal position of the pupil and the notching of
the tongue. The webbing of the toes varies in extent in the different species, but




SOUTHERN FROGS.



275



there is never any expansion of these extremities. The outer metatarsals are
completely united, and the skull is remarkable for the extent to which ossifica-
tion is carried out. In some species, sucli as the Brazilian horned frog (C. boiei),
the upper eyelid is produced into a horn-like appendage; but in others, like the
Argentine horned frog (C. ornata), this is little developed and scarcely noticeable.

The largest representative of the genus is the above-mentioned Brazilian
horned frog, which attains as much as 8 inches in length, and is one of the most
handsomely ornamented of the genus. The smaller Argentine species represented
in our illustration differs from it by the upper eyelid being only slightly
pointed and triangular, as well as by the presence of a bony shield on the back.
The skin is covered with tubercles above and granules below ; the general colour of




ARGENTINE HORNED FROGS, OR ESCUERZOS (nat. size).



'. the upper-parts being yellowish or greenish, with large olive spots surrounded by
light-coloured or golden margins, while there are sometimes wine-red lines between
the spots. These frogs, or escuerzos, as they are locally called, are abundant in
many parts of Argentina, and in damp weather may be met with crawling about
among the grass in numbers, after the manner of toads. They are exceedingly bold
and ferocious, flying fiercely at anyone who attacks them, and maintaining their
hold with the tenacity of a bull-dog, at the same time uttering a kind of barking
cry. On other occasions they give vent to a peculiarly deep bell-like note. When
in repose, escuerzos are in the habit of burying themselves in the soil with only the
top of the back exposed, in which state they are almost invisible. In this position
they lie in wait for their prey, which includes other frogs, birds, and small mammals ;
and at times they capture and attempt to swallow objects too large for their capacity.



276 FROGS AND TOADS.

Another American genus, containing a very large number of
species, is that of the leaf-frogs (Hylodes), which deserves mention
on account of the peculiar reproduction of one of its representatives, the so-called
Antillian frog (H. mart inicen sis). These frogs differ from the group to which the
last genus belongs by the absence of a bony style to the breast-bone, and the
unwebbed hind-toes ; while they are further characterised by the expansion of the
tips of the toes into smooth discs, the horizontal pupil of the eye, and the presence
of teeth on the vomer. The Antillian frog, or, as it is locally termed, coqui, is an
inhabitant of several of the West Indian Islands, and may be recognised by its
warty under surface ; the general colour of the upper-parts being grey or brownish,
with indistinct darker marking on the head and back, and crossbars on the hind-
legs; while there is a large dark mark on the temporal region, and another near
the muzzle. The remarkable fact connected with the reproduction of this species
is that such transformations as are undergone by the larvae take place within the
large eggs ; the creatures emerging from which undergo no further alteration, witli
the exception of the absorption of the remnant of the tail. In this respect the
coqui resembles the sharp-nosed frog of the Solomon Islands.

. . As the typical representatives of the family, brief mention must

be made of the piping frogs (Leptodactylus) of Central and South
America, which differ from the preceding genera in having a dagger-like bony
style to the breast-bone ; and having the pupil of the eye horizontal, and the teeth
on the vomers placed behind the apertures of the inner nostrils. Externally, these
frogs closely resemble the ordinary European water-frogs, with the exception that
the hind-toes are not webbed. In the males the humerus is expanded into a large
flange-like plate; and in the breeding-season the whole fore-limb is much swollen
for the purpose of firmly holding the female. These frogs derive their names
from their loud pipe-like croaking, which varies in tone and intensity according
to the species. Some are noteworthy from their habit of digging a hole in the
ground near water, and lining it with a layer of scum, upon which the eggs are
deposited, and left to hatch. The nests seem, however, always to be so placed
that at a certain season they will be flooded by the rise of the neighbouring watei
When first hatched, the tadpole is not unlike that of the frog, although with
relatively smaller tail ; and when the nest becomes flooded the mode of life of it
occupants is similar to that of the ordinary frog-larvae.

THE TOADS.
Family BUFONIDJE.

Passing over the unimportant family of the Dendrapkryniscidce, including
only two small South American genera, our next representatives of the
suborder are the true toads, which constitute a family distinguished by the
absence of teeth in both jaws, and the expansion of the extremities of the
transverse processes of the sacral vertebra. The vertebrae resemble those of
the typical frogs, and there is the same absence of ribs as in the latter. The
terminal joints of the toes are either blunt, or T-shaped ; and in only two out of



TOADS.



277



the eight genera is the pupil of the eye vertical. Two of the genera approximate
in character to the preceding family. The toads have an almost cosmopolitan
distribution, and while the more typical forms are characterised by their terrestrial
habits, rough skin, and creeping gait, so unlike that of the frogs, others are burrow-
ing, and others, again (Nectes}, thoroughly aquatic. Moreover, the disc-footed toads
(Nectopkryne) of Western Africa and the Oriental region, in which the toes terminate
in disc-like pads, appear to be arboreal ; while the one Mexican representative of
another genus (Rldnoplirynus) is distinguished by its ant-eating habits.

The common toad (Bufo vulqaris) is the typical representative
True Toads \ J J L

or a large genus, with some eighty-five species, ranging over the
whole world, with the exception of Madagascar, Australia, New Guinea, and the
islands of the Pacific. As a genus, the true toads are distinguished by the entire
tongue, the horizontal pupil of the eye, the freedom of the toes of the fore-foot, and



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 29 of 62)