DIRECT BENEFITS FROM MOTHS. 67 



FORE-LEG OF A CATERPILLAR, GREATLY MAGNIFIED. 



The whole interior conformation of silk-spinning 

 caterpillars differs widely from that of warm-blooded 

 animals. They have no heart, but, in its stead, a long 

 tubular dorsal vessel, running along the back, which, 

 according to Malphigi and other comparative anato- 

 mists, has a pulsation varying from twenty to a 

 hundred beats in a minute : but neither Lyonnet 

 nor Cuvier could discover any vessels branching from 

 it, so that, if analogous to blood, it has no circulation. 

 Another important distinction between these cater- 

 pillars and vertebrate animals is, that they have no 

 brain ; their nervous system consisting of ganglions, 

 or the nervous filaments united at intervals, by little 

 knobs. Neither have they lungs, and they breathe 

 by means of small spiracles, or air holes, placed in 

 the middle of the segments, or rings, of the caterpillar, 

 on each side ; these again communicate, and end in 

 the throat by means of tubes. The spinning apparatus 

 is situated near the mouth, and connected by means 

 of long slender vessels with the silk bags. 



The external tube by which the silk is produced 



