THE SILKWORM MOTH. 149 



weight evaporates previous to hatcliing, and the 

 skins in which they are contained are equal to one- 

 fifth more. If, therefore, from one ounce composed 

 of 576 grains, 48 grains be deducted for evapora- 

 tion, and 115 for the shells, 413 gi'ains will remain 

 equal to the weight of 39,l6"8 young worms ; and 

 according to this computation, 54,520" of the larvse, 

 when newly hatched, are required to make up 

 an ounce. After they part with their first skin, 

 .3840 worms are found to be this weight, so that the 

 bulk and weight of the insects have, in a few days, 

 been multiplied more tlian fourteen times. After 

 the second change, ClO larviB weigh an ounce, the 

 weight of the animals being increased, in the inter- 

 mediate time, six-fold. In the week passed be- 

 tween the second and third ages, the number of 

 worms required to make up the weight decreases 

 from 6lO to 144, their weight being, therefore, 

 more than quadrupled. During the fourth age, a 

 similar rate of increase is maintained ; thirty-five 

 woiTOS now weigh an ounce. The fifth age of the 

 caterpillar comprises nearly a third part of its brief 

 existence, and has been described by an enthusiastic 

 writer on the subject as the happiest period of its 

 life, during which it rapidly increases in size, and 

 prepares and secretes the material which it is about 

 to spin. When the Silkworms are fully grown, and 

 have arrived at that period when they finally reject 

 food, six of them make up the weight of an ounce. 



