548 Home Nature-Study Course. 



different from the first one; it is dull yellow or orange and the spiny warts are 

 black. After it experiences the comfort of the new skin it falls to again and eats 

 as fast as it can for about a week, onlj' now and then taking a little time for rest. 

 Again it finds its skin too tight and is obliged to shed it. This time the new skin 

 is bright yellow and the warts begin to show off as real ornaments ; those on top of 

 the first .segment next to the head are blue., the next two segments are orange-red 

 and all the others are blue with black spines, except on the very end segment, which 

 has one large, yellow wart ringed with black. In this new, commodious and 

 handsome skin it lives for another week eating more voraciously than before ; 

 then the skin is changed again and this time the whole body is a delicate bluish- 

 green and the big warts on the front are orange, all the others are yellow except 

 those on the first and last segments, which are blue. This is its final color and 

 form, for although it changes its skin once more it does not noticeably change its 

 color. When it reaches its full growth it is a very large caterpillar, as large as a 

 man's thumb. It continues to eat for two weeks or so after it sheds its skin for 

 the last time and then it begins to think about spinning a cocoon. It often wanders 

 about on a tree before it finds a place which it considers suitable. It starts the 

 cocoon by making a framework of silken threads, which it spins from a gland in 

 its lower lip. This framework consists of a few strands of silk, stretching from 

 a twig to a bit of leaf then looped back to the twig. It weaves the body of the 

 cocoon by laying on the silk in the shape of continuous M's or f.gure 8's. After 

 a short time the caterpillar is completely hidden from our sight by this curtain of 

 silk. How it finally finishes the cocoon on the inside no one knows, but it nuist 

 be a very skillful performance, for the lining is so close that it squeezes the c^.ter- 

 pillar. It is like a man building a box just to- fit him, always working from the 

 inside instead of the outside ; or like a woman sewing herself up in a bag. When 

 finally the cocoon is made, the ornamental skin is pushed off -at the end of the body, 

 and the pupa quite smooth and brown takes possession of its winter home. 



LESSON CXVII. 



the POLYPHEMUS. 



Preliminary Work. — The work on the polyphemus may follow in outline that 

 given for the cecropia. It might be well to interest the pupils particularly in the 

 polyphemus as a silk worm, because the silk of the polyphemus cocoon is the 

 strongest and smoothest and most lustrous and durable of any of the American 

 silk-worm cocoons. Very handsome and durable silk cloth is made from these 

 cocoons; a single one furnishing eight hundred feet of good silken thread when it 

 is softened and unwound. The only reason these moths have not been used for 

 producing silk cloth is that they are not domesticated, and are not as easily taken 

 care of as are the caterpillars of the Chinese silk-worm, a species which has been 

 domesticated for many centuries. 



In comparing the polyphemus with the cecropia the following differences shou'd 

 be noted: The cocoon is not long and cradle-shaped, but is a very blunt oval in 

 shape. It is not doul)le walled with a filling of loose silk. It is never woven 

 close upon a twig, but sometimes chances to encompass in its strands a twig or 

 leaves. Usually it is made among several leaves which are fastened to the outside 

 and it falls to the ground in the autumn and remains safe under the snow during 

 the winter. However, if it chances to be fastened to a twig it remains upon the 

 tree until spring. The common food plants of the larvae are elm, maple, chestnut, 

 walnut, beech, birch, apple, wild cherry and some others. The eggs are flat and 



