Part 11

Among Swimming Ducks damage is only done by the =Wild Duck= (Anas boschas). It breeds wherever there are fresh waters. Nests amongst grasses or swamp-plants, or in a tree. The wild ducks remain the whole winter as long as the waters are not frozen, otherwise they go off for a short time to the south. Food: the tops of stems, buds, leaves of various water-plants, also barley, oats, and other grain; water-insects, fish, and fish-spawn. These ducks also do damage in cornfields by treading down and cracking the plants.

Family: =Longipennes= (Gulls).

Usually swimming feet. Legs tolerably long, adapted for wading (Fig. 45). Wings long, pointed. Beak laterally compressed. Young nestlings (p. 51). Breed in larger or smaller flocks, usually on the coast, occasionally on the margin of fresh waters. They chiefly feed on fish, worms, molluscs, and crustacea; sometimes, in the case of a few species, on young birds and eggs, as well as mice and other small mammals. Gulls are usually of no importance in agriculture; but the =Black-headed Gull= (Larus ridibundus), which breeds on the banks of lakes and rivers, devours many cockchafers and other noxious insects. The =Herring Gull= (Fig. 45), =Kittiwake= (Larus argentatus and L. tridactylus), and a few other species, which breed on the coast, sometimes show themselves inland, especially in stormy weather; they then pursue field-voles, and catch many injurious insects.

Besides the true =Gulls= (Larus), I will only mention the =Sea Swallows= (Sterna), with forked tails.

FIG. 45.—Herring Gull (Larus argentatus). ]

CLASS III.: =REPTILIA= (REPTILES).

Cold-blooded Vertebrates (p. 19). The heart has the same structure as in Mammals and Birds, but the left and right ventricles are usually only incompletely divided from one another (p. 20). The body is invested with horny scales or with bony plates covered by a horny layer. Reptiles are very unlike Birds in appearance, but present many essential points of resemblance to them in their skeleton; indeed, during earlier geological times, there were transitional forms between the two classes. The structure of the reptile egg, too, is very similar to that of the bird’s egg; but the first has no lime-salts deposited in its shell. The egg is not hatched out by the animal itself, but exposed to the heat of the sun or to the warmth developed by decaying vegetable matter. Several reptiles (adder, for example) keep their eggs in their bodies till the young escape. Reptiles have either no limbs (snakes, a few lizards), or, at any rate, the limbs are not well developed, and are so placed that the body does not rest upon them, but is slung between them.

FIG. 46.—Common Lizard (Lacerta agilis); 2, head of the same from below; 3, tongue. ]

The Reptilia are divided into the Orders of =Crocodilia= (Crocodiles), =Chelonia= (Turtles and Tortoises), =Lacertilia= (Lizards), =Ophidia= (Snakes).

FIG. 47.—The Adder (Pelias berus). ]

Our native reptiles have no agricultural importance. I will, however, briefly mention the =Adder= (Pelias berus, Fig. 47), as it is dangerous to man. Head broad; tail much smaller than the hinder end of the body. Colour greenish grey or brownish. A black zigzag band runs along the dorsal side of the body. Length about twenty inches. The two hook-shaped poison-fangs are found in the front of the upper jaw; opening the mouth widely causes them to be erected. They are traversed by poison-canals through which the poison flows immediately into the two bloodless wounds. The adder lives in woods and on mountain slopes, where it devours mice. The poison has a decomposing action on the blood; it causes fever, and swelling of the part bitten, as well as sometimes of the neighbouring parts. The bite may be fatal. Alcohol is spoken of very highly as a remedy.

FIG. 48.—The Grass Snake (Tropidonotus natrix). ]

FIG. 49.—Blindworm (Anguis fragilis). ]

The native =Ringed Snake= (Tropidonotus natrix, Fig. 48), three feet long, is bluish with belly flecked with black and white; a yellow and a black band on the neck. It is fond of going into the water, and eats frogs, newts, and insects. The =Smooth Snake= (Coronella lævis), two feet long, is brown, with black patches on the back, which, however, do not form a continuous band. Head dark velvety black. Devours lizards and blindworms. The =Blindworm= (Anguis fragilis) is indeed snake-like, or rather worm-like (Fig. 49), but nevertheless belongs to the lizards, with which its internal structure agrees.

CLASS IV.: =AMPHIBIA= (AMPHIBIANS).

FIG. 50.—Great Crested Newt (Triton cristatus); male above, female below. ]

Cold-blooded Vertebrates (p. 19). The heart has only one ventricle and two auricles (cp. p. 21). The skin is naked, damp, usually slippery and smooth; it helps in respiration. Although several Amphibians resemble various Reptiles in outward appearance (Newt and Lizard, Figs. 50 and 46), the structure of the skeleton is quite different. Upon the whole, Amphibians resemble fishes more closely, and they breathe by gills when they are young, which strengthens the agreement. They undergo a metamorphosis. The just-hatched young at first hold fast by suction to the jelly of the spawn; they have external gills. They quickly develop a membranous margin to the body, especially round the tail, which consequently forms a sort of oar. Meanwhile internal gills develop, and the external ones disappear. The larvæ are now fish-like (“tadpoles”). The limbs quickly grow out, the lungs develop, the tail shrivels up, and the animal leaves the water. Even the adult, however, lives among damp surroundings. In the adult state the Amphibians feed on insects, worms, and snails; many species are exceedingly useful owing to this.

Amphibians are divided into two orders, the Urodela (Newts, etc.) and the Anura (Frogs and Toads). To the first belong the =Great Crested Newt= (Triton cristatus) and the =Common Newt= (Lissotriton tæniatus). Examples of the Anura are the =Edible Frog= (Rana esculenta), the brownish =Common Frog= (R. temporaria, Fig. 51), the =Common Toad= (Bufo vulgaris), and the =Natterjack= (B. calamita, Fig. 52).

FIG. 51.—Common Frog (Rana temporaria). ]

Both frogs and toads do good by devouring many noxious insects, and also, in particular, snails. Toads are often kept in greenhouses for this purpose; and in the research garden attached to the Rouen entomological laboratory the snails were entirely exterminated in 1891, as a result of introducing a hundred toads and ninety frogs.

FIG. 52.—Natterjack (Bufo calamita). ]

CLASS V.: =PISCES= (FISHES).

Cold-blooded Vertebrates (p. 19), which breathe by gills during their whole life. The heart consists only of a single ventricle and a single auricle (p. 18). The head passes immediately into the body without any intervening neck. Fishes move chiefly by means of the tail, at the end of which there is a tail-fin. This and the dorsal and anal fins lie in the median plane of the fish, while the pectoral fins, which are attached to the skull in bony fishes, and also the ventral fins, are paired structures more or less comparable to the fore and hind limbs of higher vertebrates. The skeleton of most fishes (pike, perch, carp, eel, plaice) is bony; but in a few subdivisions of fishes (sharks, skates, sturgeons, lampreys) it is cartilaginous. The skin is usually covered with thin translucent scales; but there are fishes with a smooth skin (lampreys), with prickle-like dermal ossifications (sharks), and with rhomboidal bony plates (sturgeons). As Fishes are without exception aquatic, there is no need for me to treat more specially of them here.

FIG. 53.—The Perch (Perca fluviatilis). ]

Second Sub-Kingdom: ARTHROPODA (JOINTED-LIMBED ANIMALS).

FIG. 54.—Wood-borer (Sirex); 1, larva; 2, adult insect. ]

FIG. 55.—The Large Centipede (Scolopendra morsitans). ]

FIG. 56.—Ground Beetle, with nervous system drawn in white. ]