168 



BOYS AND GIRLS IN BIOLOGY. 



self down from liigli branches when he thinks there is 

 danger near, and hide himself in the grass ; then he goes 

 back to his perch by the same thread, when the danger is 

 past. Possibly you thought this a stray cobweb that the 

 caterpillar had appropriated to himself. Not at all ; it 

 is a cable of his own manufacture. Let us see how he 

 makes it. Some of the- gum that we found in the 

 bags passes down through the fine tubes, getting smaller 

 and smaller, till it reaches the little spinning-machine 

 (spinneret) where the two fine threads are joined into 

 one ready for use whenever needed. Thus the cater- 

 pillar furnishes the raw material and spins his own 

 yarn, for which he has other uses, as we shall soon 

 see. The yarn which the silk-worm spins, you know, 

 is very valuable, and its value depends a good deal upon 

 the way in which these two threads are made into one. 

 There is still one other organ in the caterpillar. On 

 each side, in front of the spinning-bag, is another 

 smaller bag, opening into the mouth by a tube. These 

 bags contain the caterpillar's spittle, or saliva, which 

 he never uses except on proper occasions, consequently 

 caterpillars are not obliged to have spittoons in their 

 drawing-rooms. Thus, you see, the crawling cater- 

 pillar is really a very wonderful creature. He seems 

 to be higher up in the scale than either the mussel or 

 lobster, because his breathing-apparatus is more like 



