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the partial webbing of those of the hind-limbs, as well as by the breast-bone being
either cartilaginous or with only a partially ossified style. The degree of webbing
of the hind-toes varies ; and while the tips of the toes are generally simple, they
are sometimes expanded into small discs. The head may or may not have bony
ridges. The common toad belongs to a group characterised by the absence of these
[idges, and by the hind-toes being at least half- webbed ; while it is specially distin-
lished by the absence of a fold on the ankle, and by the tubercles beneath the

)ints of the hind-toes being mostly double. On the upper-parts are more or less
prominent warts, which, although frequently spiny, are not distinctly porous ; and
the glands behind the eyes are remarkably prominent, and of an elongated elliptical

)rm. In colour, the upper-parts are brownish, with darker spots or marblings ;

rhile the lower surface is whitish, more or less thickly spotted with black. A black
le runs on the outer side of the gland behind the eye ; this line, in specimens from

}hina and Japan, extending along the upper side of the flanks. The distributional
irea of the species includes Europe, Asia (exclusive of India and adjacent regions),

id North- Western Africa. Few animals have suffered more from popular supersti-
tion than the common toad, which, although practically harmless, has been almost
liversally shunned and detested. It is, however, true that the secretion from its

dn is acrid and irritating, as may be seen by the foaming lips of dogs which
ittempt to meddle with these amphibians. Sluggish and terrestrial in its habits,
the toad needs not the long and fully-webbed hind-limbs of its active cousin, the
frog ; its usual pace being a kind of crawl, although, when disturbed, it can execute
an imperfect leap. When alarmed, or threatened with danger, a toad immediately
stops and puffs out its body to its utmost capacity, at the same time causing the
acrid secretion to exude from the pores of its skin, and likewise discharging a pure
limpid fluid from a special reservoir. Of its general habits, Bell writes that the toad
" becomes torpid during the winter, and chooses for its retreat some retired and
sheltered hole, a hollow tree, or a space amongst large stones, or some such place,
and there remains until the return of spring calls it again into a state of life and
activity. Its food consists of insects and worms of almost every kind. It refuses
food which is not living, and, indeed, will only take it at the moment when it is in
motion. When about to feed, the toad remains motionless, with its eyes turned
directly upon the object, and the head a little inclined towards it, and in this attitude



278



FROGS AND TOADS.



it remains until the insect moves ; when, by a stroke like lightning, the tongue is
thrown forward upon the victim, which is instantly drawn into tin- mouth. . .
When the prey is taken, it is slightly pressed by the margins of the jaws ; but as
this seldom kills it, unless it be a soft tender larva, it is generally swallowed alive.
Toads will also take earth-worms of considerable size ; and it is a curious sight to
watch the manner in which the powerful and writhing worm is secured. If the
toad happen to take it by the middle, the extremities of the worm are twined with
great force and activity around the muzzle of its captor in every direction, in its
attempts to escape ; but the toad pushes one portion after another into its mouth,
by means of the fore-feet, until it all disappears, when it is swallowed whole."
The eggs of the toad differ from those of the frog in that, instead of forming an
irregular mass with their enclosing jelly, they are arranged in a regular, double,
and alternating series in the form of a string, which may be a yard or more in
length. These strings are generally deposited in the water about a fortnight later
than the spawn of the frog ; and it is not till autumn that the young toads corn-




Green Toad.



MEXICAN SHARP-NOSED TOAD (nat. size).

plete their metamorphosis, and forsake the water. From that of the frog, the
tadpole of the toad is distinguished by its smaller size and blacker colour.

The green toad (Bufo viridis) of Europe, Asia, and Northen
Africa, is a far handsomer species, distinguished by the presence of
fold on the ankle, and likewise by the simple structure of the tubercles on the lowc
surface of the toes of the hind-foot. There is likewise a vocal sac beneath the throat
of the male, which is wanting in the common toad. The upper-parts carry a numbei
of irregular, flattened, and porous warts ; and the glands behind the eyes, althougl
sometimes enormously developed, are generally of moderate size and more or l
kidney-shaped. The colour is olive or greenish above, generally spotted 01
marbled with a darker shade, although occasionally nearly uniform ; while th(
under-parts are either uniformly whitish, or whitish with dark spots.

Natterjack A third European species, which, unlike the last, is localb

Toad. represented in England, is the natterjack toad (B. calamita]
easily recognised by the yellow or whitish line running down the middle of the
back. From both the preceding it is distinguished by the much smaller extent of



TREE-FROGS.



279



the webbing of the hind-toes ; while there is a fold on the ankle, and the tubercles
on the joints of the lower surface of the hind-toes are to a large extent double.
The hind-limb is unusually short ; the flattened warts on the back are distinctly
porous; the glands behind the eyes are small, depressed, and either oval or
triangular; and there is an additional gland on the leg. The general colour of
the upper-parts is light olive, with darker inarblings or spots, the above-mentioned
light line being generally present; while the light under-parts are more or less
spotted with black. In its movements the natterjack is less sluggish than the
common toad, its pace being often quickened to a kind of run, during which the
body is raised considerably above the ground. It is likewise less intolerant of
drought, being frequently found in hot, sunny situations, and only resorting to the
neighbourhood of water during the breeding-season.

sharp-Nosed The Mexican sharp-nosed toad (Rhinopkrynus dorsalis), already

Toad. referred to as subsisting on white ants, is the only other member of
the family that we have space to mention, and is generically distinguished by the
long and narrow tongue being free in front, by the vertical pupil of the eye, and by
the rudimentary breast-bone. The front-toes are free, and those of the hind-limb
webbed, with simple tips ; while the general form of the body is extremely stout ;
the head small, with a long, truncated muzzle and narrow mouth ; the eyes being
small, and the limbs remarkably short. In colour this toad is olive-brown or
bluish grey above, frequently with yellowish spots on the flanks and middle of
back, those on the back sometimes uniting to form a line.

THE OVERLAPPING-CHESTED TREE-FROGS.
Family HYLID^J.

The numerous, mostly arboreal, frogs thus designated form a family compris-
some ten genera, very abundant in Australia and America, and more sparingly

^presented in Europe, Asia north of the Himalaya (one species ranging into North-
Eastern India and Burma), and
Northern Africa. While resem-
bling the toads in the expansion
the processes of the sacral

srtebra, they differ by the pre-

mce of teeth in the upper jaw,
and they are peculiar in the claw-
like form of the terminal joints
of the toes. The vertebrae are
cupped in front, and spherical
behind, and there are no ribs.

Grasshopper- The grass-

Frog. hopper-frog (Acris
gryllus) of North America is the
sole representative of a genus
characterised by the horizontal
pupil of the eye, the webbing of GRASSHOPPER-FROGS (nat. size).




2 8o FROGS AND TOADS.

the hind-toes, of which the tips are but little expanded, and the slight expansion
of the processes of the sacral vertebra. In form this little frog is slender, with a
narrow head and rather sharp muzzle ; while the skin of the upper-parts is either
smooth or slightly tuberculated, and that of the under-parts granulated. The
mottled and striped coloration is very variable, the ground-tint ranging from
reddish broy/n to green ; but there is generally a large, triangular, dark bro \vn
spot between the eyes, and sometimes a light stripe down the back. Locally very
abundant in Eastern and Central North America, the grasshopper-frog derives its
name from its piercing, strident cry, which resembles the noise of its insect name-
sake. It frequents stagnant waters, and is fond of resting on the leaves of
aquatic plants. Unlike most of its allies, it lurks among plants, and seldom, if
ever, ascends bushes or trees.
Typical Tree- Closely allied to the last are the numerous species of typical

Frogs. tree-frogs (Hyla), which are by far the most beautiful representatives
of the entire order, and are best known by the common European species. In this
genus the pupil of the eye is horizontal, the toes of both limbs dilated into discs,
and those of the hind-foot more or less extensively webbed, the tongue either
adherent or more or less free behind, and the expansion of the transverse pro-
cesses of the sacral vertebra more or less strongly marked. As in the last genus,
there are teeth on the vomers. Represented by about one hundred and fifty
species, this genus has a distribution coextensive with that of the family ; the sole
Indian member of the latter being included. The under surface of their bodies is
very different to that of the terrestrial species ; for the skin, instead of being
smooth, is covered with granular glands, pierced by numerous pores, through
which the dew or rain, spread on the surface of the leaves, is rapidly absorbed
into the system, and reserved to supply the moisture necessary for cutaneous
respiration. Except during the breeding-season, when the greater number of them
seek the water, or when they retire before the cold of winter or drought of summer
under mud, beneath stones, the bark of trees, or in other safe spots, these frogs spend
their lives among the leaves of trees, where they find alike their dwelling-places
and their hunting-grounds. As in the case A the flying frogs, their colour har-
monises exactly with their natural surroundings, and changes even more rapidl
than that of the chamseleons. So exactly indeed do they resemble the folk
among which they hide, that it is often difficult to tell frogs from leaves ; and
has been noticed that where there is the greatest variety and brilliancy of coloi
among the forest trees, the tree-frogr V heir most brilliant and varied tints.

The European tree-frog (H. arborea^ v hich is one of three species inhabitii
the Old World proper, has a wide geogranhi 1 distribution, inhabiting the great
part of Europe, Asia north of the HimaJ, v ' as far east as Japan, and North Afric
With the exception of the higher mountain ranges and the extreme north, as we
as Norway and Britain, it is spread over the whole of Europe, although varyii
locally to a considerable degree in coloration and habits. The males are furnislu
with a large external vocal sac on tlr oat, and the skin is smooth above am
granulated beneath. The general coloration may be described as greenish ubovi
and uniform whitish beneath, but there are many variations in regard to tl
markings on the upper-parts ; the typical form having a greyish or black ligl



TREE-FROGS.



281



Nesting-Habits.



edged streak extending from the nostril through the eye and ear along each side
of the body, and sending a branch upwards and forwards on the loin, while a
whitish line descends from the upper lip to the shoulder, and then runs upwards to
the eye, thus enclosing an elongated green area. In habits this frog is most active ;
and while in swimming it is nearly equal to the common frog, in leaping it is its
superior, in addition to which it is a most expert climber. When croaking, the
sac on the throat of the males becomes so inflated as to make this appendage
nearly as large as the body. Like toads, tree-frogs do not appear to touch the
insects on which they prey until these begin to move. Flies, spiders, beetles,
butterflies, and smooth caterpillars appear to form their favourite food ; although
they have been known to attack and kill humble-bees. The European species is
of very small size, but some of the American arid Australian species attain compara-
tively large dimensions, one of the largest members of the genus being H. faber,
of Brazil, which measures as much as 3i inches in length.

An interesting account of the breeding-habits of the frog last
mentioned, which in Brazil is known as the ferreiro, or smith, is given
Goeldi, whose



by Dr.
observations were made
in the Organ Mountains,
adjoining the bay of Rio
de Janeiro. This frog
makes regular pools of a
circular form in the
shallow borders of ponds
and swamps, such pools
iing surrounded by
a narrow mud-wall. In
1894 one pond contained
nine of these pools, which
serve as nests for the
tadpoles. " On the night
of the 18th of February,"
writes the describer,
"between nine and eleven
o'clock, we approached




EUROPEAN TREE-FROGS (nat. size).



the pond, occupied, as we could heaij u- 'h^ distance, by at least a dozen of the
large tree-frogs. The moon was t, ii^g brightly, and much favoured our
undertaking, but even under these rcumstances we had to accustom our sight
to discern the details in the margin, v' vegetation, and the portion somewhat
hidden in the shadow. By and by we discovered the ferreiros, some at work,
others drumming together on the walls of some pool, or in the middle of the
pond, sitting upon some floating object, such as water-plants. The vocalists, of
which we could distinguish the mod-. . ^ v inflated gular sacs, were all males."
After stating that he was posted on a side of the pond where five nests w r ere
already situated, Dr. Goeldi observes that he and his companion were fortunate
enough to see the rising of a new nest. In a certain spot he writes that " we



282 FROGS AND TOADS.

first saw some slight movement in the water, produced by something stirring
below the surface. We then soon saw a mass of mud rising to the surface, carried
by a tree-frog, of which no more than the two hands emerged. Diving again, after
a moment's time, the frog brought up a second mass of mud, near the first. This
was repeated many times, the result being the gradual erection of a circular wall.
From time to time the head and front part of the body of the builder appeared
suddenly with a load of mud at some point ; but what astonished us in the highest
degree was the manner in which the frog used its hands for smoothing the mud-
wall, as would a rnason with his trowel. And by examining the hands of this
hyla, it will readily be understood how they are most serviceable trowels, their
terminal joints bearing large expansions. This careful process of smoothing could
be better observed as the wall gradually heightened, until it reached about four
inches, when the frog was compelled to come out of the water. The parapet of
the wall receives the most careful smoothening, the outside being neglected, and
the levelling of the bottom attained by the action of the lower surface of the
creature's body, aided by the hands. The aspect of the pool may be compared to
the crater of a volcano, or a vessel of a foot in diameter filled with water. Although
the female undertakes the entire task of building, she is incommoded the whole
time by the male sitting on her back. Should he be frightened from his post, he
will soon emerge from the water at a distance of a few feet, when, if signs of
danger be wanting, he will climb the walls of the nest and regain his original seat."

Another Brazilian tree-frog of the same genus (H. goeldii) breeds in the
water contained in the central cup of certain trees belonging to the Sromeliacece.
Dr. Goeldi states that the first specimen found was a female, carrying on her
back a large globular mass of whitish eggs. When put in a vivarium, " for a
few days the egg-mass remained attached to the mother's back. But suddenly
it fell away, and simultaneously I saw in the glass some small, nearly black
coloured frogs, all provided with the anterior and posterior legs, together with
a larval tail of medium or rather small size."

Yet another tree-frog from Brazil (H. nebulosa) has acquired the remarkable
habit of depositing its eggs in the sheaths of old and decaying leaves of bananas.
The writer from whom we have been quoting states that this frog " glues its lumps
of eggs on the edges and on the inside of banana leaves, where, even during the
hot hours of the day, sufficient coolness and moisture are preserved. These lumps
are enclosed in a frothy, whitish substance, comparable to the scum formed In-
certain Cicadidce. Sometimes the tailed larvae are seen struggling in this frothy
mass. If put into fresh water, all will die in a few hours."
Pouched Tree- On account of the peculiarity of their reproduction, mention

Frogs. must be made of the curious pouched tree-frogs (Nototrema), dis-
tinguished from the typical genus by the presence of a backwardly -opening pouch
at the hinder-end of the back in the females. These frogs are represented by some
half-dozen species, mainly confined to Central and Western Tropical America,
although one of their number is found on the eastern side of that continent at
Pernambuco. The pouch of the female is extended beneath the skin of the back
and sides to form a very large chamber, in which the eggs and tadpoles undergo
the whole of their transformations. The eggs, generally fifteen or sixteen in



TOAD-FROGS. 283

number, appear to be placed in the pouch by the male, who employs his hind-feet
for the purpose ; and they are remarkable for the large relative size of the yolk.
The tadpoles, when first hatched, are peculiar in having a bell-shaped structure for
the protection of their two pairs of external gills.



THE TOAD-FROGS.
Family PELOBA TIDJE.

The fifth family of the order belonging to the section with overlapping
cartilages to the metacoracoids comprises eight genera, which may be collectively
termed toad-frogs, since they come neither under the designation of toads or frogs.
Agreeing with the tree-frogs in the presence of teeth in the upper jaw, they may
be distinguished by the much greater expansion of the processes of the sacral
vertebra, ribs being absent, and the terminal joints of the toes simple. In all
the forms the pupil of the eye is vertical ; and whereas the majority of the genera
agree with the preceding groups in having the articular cup at the front and the
ball behind, in a few this arrangement is reversed. The family is distributed
over Europe, the Oriental region, North America, and New Guinea ; the various
genera having a more or less restricted geographical range.

Brown The brown toad-frog (Pelobates fuscus) is the typical representa-

Toad-Frog. ^ ve o f a genus containing two European species, neither of which are
found in Britain. They are characterised by the rod at the end of the backbone
being welded to the sacral vertebra, and by the extensive webbing of the hind-toes ;
he presence of a bony style to the breast-bone, coupled with the want of an
ixternally visible ear-membrane, serving to distinguish them from an allied North
merican genus (Scaphiopus). The brown toad-frog is a rather large species,
sually measuring from 2J to 3 inches in length, and having a smooth brown skin,
arbled on the upper-parts with darker markings ; a spur which is present on the
metatarsus being yellowish brown. The males have no vocal sac, but are furnished
ith a large elliptical gland on the upper surface of the fore-limb. This species
s decidedly local, and in some districts is replaced by the allied P. caltripes, easily
listinguished by the black spur on the metatarsus. Spending only a few days
luring the breeding-season in the water, it is essentially a land animal, generally
requenting spots with a sandy soil. Here, with the aid of its metatarsal spur,
t rapidly excavates hollows in the ground, throwing out the earth backwards,
d soon partially concealing itself. An aperture is, however, always left to the
excavation, and should the rays of the morning sun reach its occupant, the burrow
s quickly deepened. In its movements the toad-frog is more active than the
-oads, approaching in this respect the frogs, as it takes considerable leaps, swims
strongly, and burrows with rapidity. The breeding-season takes place in April,
luring which time the males utter a loud croaking, accompanied in a lower tone
>y the females. The eggs are laid in strings of about a couple of feet in length ;
ind are taken from time to time by the male and carefully deposited round
l eeds, grass, or other plants growing near the edge of the water. In from five to
ix days the small black tadpoles are hatched out; and in the course of four



284 FROGS AND TOADS,

months these have completed their development and leave the water. When an
adult toad-frog is suddenly seized or pinched, it utters a cry like the mewing of a
kitten, at tin; same time emitting a pungent vapour witli a strong odour of garlic,
both these being apparently intended us a means of defence,

Of the remaining genera, Pelodytes, as represented by the
punctured toad - frog (P. punctatus) of Western Europe, and the
Papuan JBatrachopsis, differ from the preceding in that the sacral vertebra
has two condyles for articulation with the rod forming the termination of the back-
bone, the hind-toes being slightly webbed. In the Oriental genus Leptobrachium,
there is but a single condyle for the articulation of the rod-like bone.

Allied In the Miocene rocks of Europe there occur remains of numerous

Extinct Frogs, f rO gs which are assigned to an extinct genus, Palceobatrachus, regan led
as representing a family (Palceobatrachidce) connecting the present one with the
under-mentioned Xenopodidce. In these extinct forms the upper jaw is toothed,
the transverse processes of the sacral vertebra have expanded extremities; the
sacral vertebra articulates with the terminal rod of the backbone by means of two
condyles ; the vertebrge have their articular cup in front ; and there are 110 ribs.



THE DLSC-TONGUED FROGS.
Family DlSCOGLOSSID^E.

The disc-tongued frogs, as the members of this group may be called, form a
small family represented by four genera and seven species, inhabiting the northern
half of the Old World and New Zealand. As a family, these frogs are characterised
by the presence of teeth in the upper jaw, the expansion of the processes of the
sacral vertebra, the presence of short rudimentary ribs, and the circumstance that
in the bodies of the vertebrae the articular cup is placed at the hinder-end, and the
ball in front. In both the latter respects these frogs resemble the salamanders and :
newts, and they may accordingly be regarded as some of the least specialised repre-
sentatives of the order. Their remains occur abundantly in the middle Tertiary
rocks of Europe. The family derives its name from the disc-like form of the
tongue, which may be either free or adherent. From all the forms hitherto described, j
the tadpoles, after shedding the external gills, differ in having the breathing-pore
situated in the middle of the under surface of the body, instead of on the left side>ij
Fire-Bellied From the painted frog (Discoglossus pictus) of Southern Europe 4

Fr - and North- Western Africa, which alone represents the typical genu|i
of the family, the fire - bellied frog (Bombinator igneus), represented in the ]
figure on p. 257, is distinguished by the absence of an external tympanic mem+jl
braue to the ear; while it is further characterised by the adherent tongue, the I
triangular form of the pupil of the eye, and the great expansion of the extremities ]
of the transverse processes of the sacral vertebra. This frog, which inhabits |
Europe and Asia, although unknown in the British Islands, has the skin very warty
on the upper-parts, while beneath it is nearly smooth. In colour it is olive above,
with or without black marblings ; while beneath it is orange or yellow, marbled J
with black. The males are devoid of a vocal sac, but during the breeding-season t



DISC-TONGUED FROGS.



285



Midwife-Frogs.



i they develop black rugosities on the inner side of the fore-arm, as well as on the
inner tubercle of the metacarpus, and on the two innermost front-toes. There are



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 30 of 62)