Spiders

Good Words. Spiders are not insects, as most people think. ïkore is precisely the same relationship between a spider and an insect that there is betW6en a cow and a oodfish. The cow and the fish are both vertebrates, and the spider and the insect are both annulates, but there the reseniblanee censes. In every ottier point of structure they diffur "widely froni each pther. The spider has eight legs, whereas an insect can not have more than six. The nervous system is constructed on a totally different principie, and so are the circulation and respiration. Tho eyes are different, the insects having many compound eyes, and the spider never having more than eight, and all of them simple. Then, a spider has no separate head as is the cfse with the insects, the head and thorax being f used together. Neither does the spider pass through the series of developments which we cali "transformadons." When tho young spider is hatched, it is a spider, and retains tho same shape through its whole life. Again, no insect that is at present known can spin silken threads. Tako the silkworni as a familiar example. The silk is spuu by the cat9rpillar and not by the moth. Now, the spider can produce threads throughout the whole of his life. lt possesses, moreover, the faculty of producing different kinds of silk, according to tiie object for which it is needed. If we watch tho first of these creatures, we may see all these silks produced. The web of the diadeni spider is made of radiating cables, like the spokes of a wheel, and having a silk thread wound spirally over the spokes. The whole web is susoended by cables like those which form the spon es, and guy ropes of similar structure support it on every side. A olut-bottle fly now comes buzzing along and blunders against one of the supporting cables. It is not arrested by the cable but falls upou the net. where itis at once caught. IL we examine the web with a tolerably powerf ui magnifying glass, we shall see that the cables and spokes are qaite smooth, while the spiral thread is covered with little globules of a gummy character. There are about 1,400 of these glóbulos in each inch of thread, and on an average a complete web contains 87,000 of them. These globules act juat like bird lime, and the moment that an insect touches ono of them with its leg or wing,it is held tightly by the gum.