132 



THE ANIMAL KINGDOM. 



the gorgeously painted butterfly or the busy bee ; but this 

 perfect condition does not endure long, for most of them 

 die immediately after they have laid their eggs. The Bees 

 and Ants, however, continue much longer in the complete 

 state. 



The liquid which represents the blood of insects is 

 cold, transparent, and nearly colourless ; the heart is a 

 long tube running along the back, and is therefore called 

 the dorsal vessel. This fluid is not always contained in 

 vessels, but is diffused between the muscles and other 

 organs. 



The eyes of insects are as wonderful as the other 

 portions of their construction, and are of two sorts 

 simple and compound. Nearly all insects have two com- 

 pound eyes, but some have the simple ones instead, 

 whilst others have both kinds. 



Thus, the bee has three simple eyes, which seem like so 

 many gems set in front of the forehead. Then on each 

 side of the head is a large projecting mass, which, on 

 being examined with a microscope, is found to be made 

 up of thousands of small eyes, each of which is perfect in 

 itself, yet all uniting in one great nerve. Each of these 

 minute eyes has a six-sided face, each has its retina, and 

 each has its separate nerve which unites it with the main 

 nerve.* 



The compound eye of an ant has fifty of these separate 

 lenses ; that of a common house-fly, four thousand ; that 

 of a butterfly, seventeen thousand; and that of the 

 Mordella beetle, twenty -five thousand. 



The annexed pictures (Figs. 90 to 94) show the meta- 

 morphosis of insects the example chosen being the 

 common Silkworm, or, more properly, the silk-spinner; 

 for you will by this time be quite clear that the caterpillar 



* See " Our Bodies," Catefell's Primary Series, p. 101 



