ORDER IX.-CENTIPEDES, SPRING-TAILS, ETC.

APTERA (WITHOUT WINGS).

THE insects, and the tribes allied to insects, which Linnæus included in this division, are now arranged in four orders:1. Centipedes (Fig. 47) and others possessed of numerous feet, as the Millipede (Julus, Fig. 97.)

Fig. 97.-JULUS.

II. Spring-tails, (Fig. 98). Their forked tail is kept under the body when not in use; when unbent it acts as a spring, and has given origin to the English name.

III. Lice (Fig. 99) and other insects, which live as parasites on man and the lower animals; and

IV. Fleas (Fig. 100). The mouth is formed for suction, and the hind legs for jumping.

THE present class includes Spiders, Scorpions, and Mites. They do not, like insects, undergo transformations; and some among them breathe not by tubes, but by lungs. They differ from the true insects also in having eight legs instead of six. The eyes vary in number and position, but are never compound.

All Spiders secrete a poisonous fluid, which is, no doubt, formidable and even fatal to insects, but produces little effect on the human frame. The poison is conveyed through a perforated fang in the mandibles or jaws. In the

Scorpion (Fig. 102), on the contrary, it is lodged in the extremity of the slender flexible tail, and the wound is inflicted by the sting by which the tail is terminated.

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Fig. 102.-SCORPION.

That any creature could be found to fabricate a net, not less ingenious than that of the fisherman, for the capture of its prey; that it should fix it in the right place, and then patiently await the result, is a proceeding so strange, that if we did not see it done daily before our eyes by the common House-spider and Garden-spider, it would seem wonderful. But how much is our wonder increased when we think of the complex fabric of each single thread, for it is made up of more than a thousand threads still more delicate; so that, even when it is so fine as scarcely to be visible to our eyes, it is not a single line, but is in reality a rope composed of more than a thousand strands. This is ascertained by counting the number of little teats at the hinder extremity of the body, whence the threads proceed, and examining the multitude of minute orifices, of which each of them is com

posed. Add to this, as an example of the wonders which the most common things exhibit when carefully examined, the net of the Garden-spider consists of two distinct kinds of silk. The threads forming the circles are composed of a silk much more elastic than that of the rays; and are studded over with minute globules of a viscid gum, sufficiently adhesive to retain any unwary fly which comes in contact with it. In ordinary circumstances, the threads lose their viscidity by exposure to the air, and require to have it renewed every twenty-four hours. Any observer, by scattering a little fine dust over the web, may satisfy himself that it is retained only on the circles where the minute globules are placed, and not upon the radii, or lines which come from the centre to the circumference. The nets of some spiders are constructed under water-the secretion being insoluble—and are spread out for the capture of aquatic insects.

A great deal of false commiseration has been bestowed upon the flies which fall victims to the voracity of the spider, who has accordingly been regarded as "Cunning and fierce, mixture abhorred." But, considered aright, there is no cruelty in any animal exercising, for its support, those powers with which it has been endowed by its Creator. It does not kill from wantonness, but from necessity. It must kill, or it must cease to live.

Spiders have been divided into families, which present very considerable differences in their modes of life and in their habitations. The Mygale forms a subterra

neous tube or gallery, lines it with silk, and constructs a door formed of several coats of cemented earth and silk. "This door (Fig. 103) the ingenious artist fixes to the entrance of her gallery by a hinge of silk; and, as if acquainted with the laws of gravity, she invariably fixes the hinge at the highest side of the opening, so that the door, when pushed up, shuts again by its own weight." The part against which it closes with great accuracy, and the defences by which it is secured, are not less excellent as mechanical contrivances.

The female Spider is remarkable for her parental affection. Professor Hentz thus describes the habits of one species. "When a mother is found with the cocoon containing the progeny, if this be forcibly torn from her, she turns round and grasps it with her mandibles. All her limbs, one by one, may then be torn from her body without forcing her to abandon her hold. But if, without mangling the mother, the cocoon be skilfully removed from her, and suddenly thrown out of sight, she instantaneously loses all her activity, seems paralysed, and coils her tremulous limbs, as if mortally wounded: if the bag be returned, her ferocity and strength are restored the moment she has any perception of its presence, and she rushes to her treasure to defend it to the last."