INSECTS 171 



until May, the females retire to cool forest-brooks, or springs, or other supplies of 

 water to bring forth their young, which are sometimes more than thirty in number. 

 The eggs in the ovaiy, which begin to mature after the birth of the young, are 

 fertilised by milt previously taken up by the females and preserved in special 

 receptacles. By the autumn they have developed into fairly large tadpoles, which 

 are not born till the following spring. The pregnancy of the female salamander, 

 therefore, lasts nearly a whole year ; the female, for instance, which in the spring 

 of 1910 fertilises her eggs with the milt collected in 1909, and preserved in her 

 receptacle for nearly a twelvemonth, then takes up fresh milt, gives birth in 

 the spring of 1911 to the young sprung from these eggs, and fertilises the eggs 

 maturing meanwhile with the milt taken in during the spring of 1910. 



The young tadpoles, endowed with lightning-like rapidity of movement, live 

 on small crustaceans at first, and then on worms : they develop into lung-breathers 

 in the water, which they leave between June and August, but, earlier or later, 

 according to the time of their birth, requiring at least two years to become 

 mature. Salamanders are the most lethargic of European amphibians. Their 

 movement is a laboured crawl, by slowly shifting their four heavy feet forward 

 and sideways, and by a lateral bending of the body and tail. Their progress in 

 water, in which their motive power lies almost entirely in the tail, is more walking 

 or water-treading than swimming, properly so called. Nor is the serenity of the 

 salamander disturbed when in search of food. Slowly it drags itself nearer to the 

 prey it has espied, and only a slight forward thrust of the head betrays its 

 intentions. These sluggish animals are not, however, without some gleams of 

 intelligence ; in captivity they gradually come to know the regular feeding-place, 

 and go there in the evening ; but if no food has been forthcoming for a few 

 days in succession, they do not repeat the visit. They also respond to a rap on 

 the glass of their case and when captive have been heard to make a sound like 

 iilciik and a kind of twitter. 



Among the inhabitants of the European woodland, the insects 

 Insects. 



are by far the most numerous. Indeed, no class of the animal 



kingdom is represented by so many species, while scarcely any is so easily identified. 



Their structure is so well known that it will be enough to mention that in all adult 



insects the body consists of three principal parts — head, thorax, and abdomen ; but 



in the young and undeveloped state they differ considerably from the perfect auimal, 



into which they develop either by complete metamorphosis — larva, pupa, and 



imago — or by a less complex transformation. The head is always freely movable, 



and has, first of all, two antennae, and also, in most cases, two immovable so-called 



compound eyes placed near together, their surfaces consisting of numerous 



hexagonal facets, every one of which is really a separate eye. Besides these, 



many insects have on their forehead, or in the middle of their head, two or three 



small simple eyes, not placed together, and not consisting of a series of adjacent 



facets. In the classification of insects, it is of particular importance to consider 



the nature of the feeding-organs. Insects may either have a mouth adapted for 



biting, or one specially modified for sucking ; the former consisting of freely 



movable, that is to say distinct, parts, while in the sucking apparatus these struc- 



