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 slugs, 

 snails, insects, etc., swallowing large beetles whole, and devouring several at a meal. 

 The frog captures its prey by suddenly throwing forwards the tip of its tongue, 

 which is invested with a viscid secretion, upon the insect or slug, and then as 

 quickly withdrawing it to its normal inverted position. So rapid is the whole 

 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 in 

 water they swim with the hind-limbs alone. 



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

 America, represented in the figure on p. 259, the European frogs are 

 mere dwarfs ; but the largest species of all is Guppy's frog (R. guppyi), from 

 the Solomon Islands, in which the length of the head and body is upwards of 9 

 inches. The bull-frog is one of those species in which the tips of the toes are 

 pointed, and it is especially characterised by the web extending to the tip of the 

 fourth toe of the hind-foot, the large size of the aperture of the ear, and the 

 relative length of the hind-leg ; the two latter characters distinguishing it from 

 Montezuma's frog (R. montezumce), of Mexico. The body has no lateral glandular 

 fold ; and the vocal sacs of the males are internal. In colour the bull-frog is brown 

 or olive above, with darker marblings ; the under-parts being either uniformly 

 coloured, or marbled with brown. In length it measures from 7 to 7£ inches, 

 exclusive of the legs. More abundant in the southern than in the northern 

 portion of its habitat, the bull-frog is generally met with in rivers and streams 

 well shaded with trees or bushes, where it may be seen in numbers basking in 



