The male has a feeble voice, which sounds like "ha-a, ha-a-a," or "wa-wa-wa," uttered in rapid succession. The pairing season lasts a long time, in Algeria from January to October, but a much shorter time in the north of Portugal, where it extends over the spring and summer months. Boulenger has made extensive observations on many specimens kept in captivity. The embrace, which never lasts long, is lumbar. The eggs are small, 1 to 1.5 mm. in diameter, dark brown above and greyish below, each surrounded by a gelatinous capsule of 3-7 mm. in diameter. The eggs are laid singly, and a set amounts to from 300 to 1000, the whole mass sinking to the bottom of the pool. Each female lays several times during the season. The eggs are developed very rapidly, the larvae escaping sometimes after thirty-six hours, but usually from the second to the fourth day. The external gills are lost on the seventh day, when the tadpoles are 11 mm. long; the hind-limbs appear on the tenth, and after four weeks the tadpoles reach their greatest length, namely from 25-30 mm. The fore-limbs appear on the thirtieth day, and a few days later the most precocious specimens leave the water and hop about. Others, however, of the same brood took from two to three months in metamorphosing.
This species lives on insects and worms, and can swallow its prey under water.
Bombinator.–The tympanum is absent and the Eustachian tubes are very minute. The pupil is triangular. The omosternum is absent. The vertebrae are absolutely epichordal. The fingers are free, the toes are webbed. The upper parts are uniformly dark, and are covered with small porous warts. The general shape of the head and body is depressed or flattened downwards. The habits are eminently aquatic. This genus consists of three species, two of which are European, the third Chinese.
B. igneus.–The under parts are conspicuously coloured bluish black with large irregular red or orange-red patches; the upper parts are more or less dark grey or olive black. The iris is golden, speckled with brown. The male has a pair of internal vocal sacs by which the throat can be inflated; nuptial excrescences are developed on the inner side of the fore-arm and the first two fingers. Total length from 1½ to 2 inches, the males being generally smaller than the females. This "Fire-bellied toad," the "Unke" of the Germans, is essentially a native of lakes, ponds, and other standing waters of the plains.
It ranges through the whole of North Germany, Bohemia, and Hungary into Russia, eastwards as far as the Volga. The latter river, the Danube, and the Weser form, roughly speaking, its boundaries; northwards it extends into Denmark and the southern extremity of Sweden.
Fig. 31.–Bombinator igneus. × 1. Fire-bellied Toad. Two of them in "warning" attitude.
B. pachypus.–The under parts are yellow instead of red. The male is devoid of vocal sacs, but has nuptial excrescences on the under surface of most of the toes, in addition to those on the fore-arm and fingers. The "Yellow-bellied Toad" is the representative of the red-bellied species in Southern and Western Europe, preferring, although not exclusively, the hilly and mountainous districts. It ranges from France and Belgium through South-Western Germany, continental Italy, and the whole of Austria and Turkey in Europe. Where both species meet, for instance in the hilly districts between the Weser and the Rhine, in Thuringia and in Austria, the predilection of the yellow-bellied species for the hills, and that of the other for the plains, is well marked.
While B. igneus prefers standing waters with plenty of vegetation, B. pachypus is often found in the smallest occasional puddles produced by recent rain, for instance in the ruts of roads. Both species have otherwise much in common. They are essentially aquatic. They hang in the water, with their legs extended, nose and eyes just above the surface, and bask or lie in wait for passing insects, the fire-bellied kind preferring to conceal itself in the vegetation of the margins of ponds. During the pairing season, in Germany in the month of May, they are very lively and perform peculiar concerts, one male beginning with a slowly repeated note like "hoonk, hoonk," or "ooh, ooh," in which all the other males soon join, so that, when there are many, an almost continuous music is produced. This sound is not at all loud, a little mournful and very deceptive. It appears to be a long way off, certainly at the other end of the pond, until by careful watching you see the little creature almost at your very feet. But on the slightest disturbance the performance ceases, they dive below and hide at the bottom. The yellow-bellied kind, when surprised in a shallow puddle, skims over the mud, disturbs it, and allows it to settle upon its flat body, so that nothing but the little glittering eyes will betray its concealment. When these toads are surprised on land, or roughly touched, they assume a most peculiar attitude, as shown in Fig. 31. The head is partly thrown back, the limbs are turned upwards with their under surfaces outwards, and the whole body is curved up so that as much as possible of the bright yellow or red markings of the under parts is exposed to view. The creature remains in this strained position until all danger seems passed. In reality this is an exhibition of warning colours, to show the enemy what a dangerous animal he would have to deal with. The secretion of the skin is very poisonous, and the fire-toads are thereby well protected. I know of no creature which will eat or even harm them. I have kept numbers in a large vivarium, together with various snakes, water-tortoises, and crocodiles, but for years the little fire-bellies remained unmolested, although they shared a pond in which no other frog or newt could live without being eaten. Hungry water-tortoises stalk them under water, touch the intended prey with the nose in order to get the right scent, and then they withdraw from the Bombinator, which has remained motionless, well knowing that quick movements, or a show of escape, would most likely induce the tortoise to a hasty snap, with consequences to be regretted by both.
After they have been handled frequently, they do not readily perform, but simply lie still, or hop away. Miss Durham experienced considerable difficulty in inducing her tame specimens to assume and to keep up the correct warning attitude. The statement that they "turn over on the back" is a fable, graphically fixed in various illustrated works.