Woodside. 1 5 



intestine. As might be expected, we find that those 

 animals which live on very soluble and easily-digested 

 material have short alimentary canals, whilst those which 

 live on harder and more indigestible material have longer 

 ones. Nature throws away no chance of getting the greatest 

 amount of nutritive material from the food, whilst at the 

 same time she does no unnecessary work. The method of 

 digestion carried on in the spider follows out this rule, and 

 is almost exactly identical with that of a butterfly or moth r 

 its circulation and respiration being also very similar. 



The eyes of spiders, however, are very different from 

 those of most insects. In the caterpillar of a butterfly there 

 are six pairs of eyes, six eyes being placed on each side of 

 the cheek in lunular form, and each eye consists of a simple 

 convex lens. When the caterpillar has become a butterfly 

 the eyes are very different. Now there is one large eye on 

 each side, compound in structure, convex in shape, made up 

 of some thousands of hexagonal facets crowded together. 

 The spider never has compound eyes ; the number varies in 

 the different species, although usually there are eight. 

 These are simple and immovable, but as the eyes are spread 

 over a considerable area, and the visual axes lie in various 

 directions, the spider is able to get almost as wide a field 

 of vision as if it could turn its head or move its eyes. 

 Sometimes the eyes are arranged in two, sometimes in three 

 rows, and this arrangement is very important to the 

 scientific naturalist. 



Under the microscope the eyes of butterflies and moths 

 attract us by the remarkable minuteness and excessive 

 number of the facets into which they are divided. The 

 eyes of spiders have no such minute divisions, but those of 



