312 



THE GUIDE TO NATURE. 





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FIRST OR BABY AGE OF THE SILKWORM. 

 Silkworms in this picture are about four or five days old. Some of them are now 

 in molt while others are about to enter the first molt or a short period of sleep. 



and in Europe since the sixth century, 

 and from which the ordinary silk of 

 commerce is produced, is the larva or 

 caterpillar of a medium-sized moth, 

 which feeds upon the leaf of the mul- 

 berry tree. This insect known to 

 science as Bouibyx mori, belongs to 

 the order Lepidoptera. family Bomby- 

 cidae, or the "Spinners," and is popu- 

 larly called the mulberry silkworm. 



When the mulberry leaves, the fond 

 of the worms-to-be, begin to unfold in 

 the spring, the eggs may be hatched 

 by exposure for ten or twelve days to 

 a warm temperature. The larva spends 

 most of its time in feeding; it grows 

 rapidly and finally attains a length of 

 about 3 inches. 



The larval stage lasts from about 

 thirty to thirty-five days. Tt is divided 

 into five different ages, separated by 

 what are called molts, at which time 

 the worm casts its skin. The rapid 

 increase in size of the insect renders 

 the original skin too small to allow 

 for its growth, and hence four molts 

 occur. When the full-grown worm is 

 ready to spin its cocoon, it crawls over 

 the leaves, shrinks somewhat in size, 



and, according to the race of the worm, 

 is now white or yellow, ,and semi-trans- 

 parent. Climbing upon some suitable 

 place it commences to throw out 

 threads of silk at the rate of sixty-five 

 motions of its head per minute, or 

 three hundred thousand in building its 

 cocoon. The thread of a cocoon is 

 continuous and varies in length from 

 750 yards to 1,200 yards. Cocoons 

 vary also in weight from 275 to 400 to 

 the pound for newly spun, or from 450 

 to 600 to the pound for dried cocoons. 

 It requires three and three-quarters 

 pounds of cocoons to produce a pound 

 of reeled or raw silk, a pound of raw 

 silk being sufficient to make at least 

 10 yards of the very best silk. In from 

 two to three weeks the covering of 

 the chrysalis, which is enclosed in the 

 cocoon, splits, and the cream-colored 

 moth within secretes a liquid which 

 moistens the end of the cocoon and 

 dissolves the hard, gummy lining. 

 Then, in the early morning hours, the 

 moth, with crimped and damp wings, 

 emerges; a short time afterwards the 

 wings become unfolded and dry and the 

 mother moth begins laying her eggs. 



