INSTINCT. 



11 



forming a dike across the stream, almost straight 

 where the current is weak, but where it is more 

 rapid, curving more or less, with the convex 

 side opposed to the stream. They construct 

 these dikes or dams of the same materials as 

 they do their lodges, viz. of pieces of wood of 

 any kind, of stones, mud, and sand. These 

 causeways oppose a sufficient barrier to the 

 force both of water and ice ; and as the willows, 

 poplars, &c. &c. employed in constructing them 

 often strike root in it, it becomes in time a 

 green hedge in which the birds build their 

 nests. 



" By means of these erections the water is 

 kept at a sufficient height, for it is absolutely 

 necessary that there should be at least three 

 feet of water above the extremity of the entry 

 into their lodges, without which, in the hard 

 frosts, it would be entirely closed. This entry 

 is not on the land side, because such an open- 

 ing might let in wild animals, but towards the 

 water. 



" They begin to excavate under water at the 

 base of the bank, which they enlarge upwards 

 gradually, and so as to form a declivity, till 

 they reach the surface ; and of the earth which 

 comes out of this cavity they form a hillock, 

 with which they mix small pieces of wood and 

 even stones ; they give this hillock the form of 

 a dome from four to seven feet high, from ten 

 to twelve long, and from eight to nine wide. 

 As they proceed in heightening, they hollow it 

 out below, so as to form the lodtre which is to 

 receive the family. At the anterior part of this 

 dwelling, they form a gentle declivity termina- 

 ting at the water, so that they enter and go out 

 under water. 



" The interior forms only a single chamber 

 resembling an oven. At a little distance is the 

 magazine for provisions. Here they keep in 

 store the roots of the yellow water-lily, and the 

 branches of the black spruce, the aspin, and 

 the birch, which they are careful to plant in the 

 mud. These form their subsistence. Their 

 magazines sometimes contain a cart-load of 

 these articles, and the beavers are so industrious 

 that they are always adding to their store."' 



The nests so admirably constructed by what 

 have been called the perfect societies of insects, 

 the white ants or termites, the ants or formicae, 

 the bees, wasps, and humble bees, are well 

 known, and have been often described. The 

 materials used by the two first genera are chiefly 

 clay, with bits of straw or wood, cemented by 

 animal secretions ; the bees manufacture wax 

 for the purpose. 



" The wasps and hoi-nets are remarkable for 

 the well-known curious papier-mache edifices, 

 in the construction of which they employ fila- 

 ments of wood, scraped from posts and rails 

 witli their own jaws, mixed with saliva, of 

 which the hexagonal cells in which they rear 

 their young are formed, and often their combs 

 are separated and supported by pillars of the 

 same material ; and the external walls of their 

 nests are formed by foliaceous layers of their 

 ligneous paper." f 



* Kirby, vol. ii. p. 510. 

 t Kirby, loc. cit. p. 335. 



" The tree-ants, again, are remarkable for 

 forming their nests on the boughs of trees of 

 different kinds; and their construction is sin- 

 gular, both for the material and the architec- 

 ture, and is indicative of admirable foresight 

 and contrivance ; in shape they vary from glo- 

 bular to oblong, the longest diameter being 

 about ten inches, and the shortest eight. The 

 nests consist of a multitude of thin leaves of 

 cow-dung, imbricated like tiles upon a house, 

 the upper leaf formed of one unbroken sheet 

 covering the summit like a skull-cap. The 

 leaves are placed one upon another in a wavy 

 or scalloped manner, so that numerous little 

 arched entrances are left, and yet the interior is 

 perfectly secured from rain. They are usually 

 attached near the extremity of a branch, and 

 some of the twigs pass through the nest. A 

 vertical section presents a number of irregular 

 cells, formed by the same process as the exte- 

 rior. Towards the interior the cells are more 

 capacious than those removed from the centre, 

 and an occasional dried leaf is taken advantage 

 of to assist in their formation. The nurseries 

 for the young broods in different stages of 

 developement are in different parts of the 

 nest."* 



What is most peculiar in the habitations of 

 all these " perfect societies of insects," is the 

 formation, by the same working members of 

 these societies, of cells of different size and form, 

 suited for the different classes or ranks of indi- 

 viduals which, as we shall afterwards state, 

 each of these associations comprises ; and the 

 occasional alteration of the size and form of the 

 cells, when circumstances occur, which will 

 be afterwards mentioned, to make an alteration 

 of their destination advisable. 



There are other examples among insects, of 

 imperfect societies or associations, found tempo- 

 rarily and during the larva state only, which 

 unite in forming tents under which they feed, 

 and which shelter them from sun and rain. 

 This is done by the larvae of several species of 

 butterfly and moth.-)~ 



4. The next instincts which may be noticed 

 under this head are those connected with the 

 hi/ber-nation of animals ; for in almost every case 

 in which this faculty (which is found so gene- 

 rally in the lower tribes, particularly reptiles and 

 insects, as well as in the order Cheiroptera and 

 several others of the higher animals,) exists, there 

 is attached to it some instinctive propensity, 

 prompting the animal, even although it be not 

 one of those which form houses for themselves, 

 at least to search for some suitable residence in 

 which it may be sheltered during the winter, 

 whether under ground, under stones or timber, 

 under the bark of trees, &c. ; and it is very re- 

 markable that their hiding places are often 

 found, or formed, long before the weather has 

 become very cold. " I am led to believe from 

 my own observation," says Mr. Spence, " that 

 the days which the majority of coleopterous 

 insects select for retiring to their hybernacula are 

 some of the warmest days of autumn, when 



* Ibid. p. 340. 



t Spence and Kirby, vol. ii. p. 21. 



