THE CLASSIFICATION OF INSECTS 177 



of disuse. The eggs, about 300, are laid by the female on any 

 bit of cloth or paper provided for her by the silk-worm growers. 

 In the annual race of silk-worms, i.e., the one which produces 

 but one generation a year, the eggs go through the winter and 

 hatch in the following spring at the time the mulberry trees 

 begin leafing out. Other varieties produce two (bivoltins), 

 three (trivoltins), and even five or six (multivoltins), genera- 

 tions a year. The larvae, or " silk- worms," must be abundantly 

 fed with either mulberry or osage orange leaves from which 

 all rain or dew drops must be wiped off. When very young 

 they are fed but two or three times a day, but later in their 

 life must have seven or eight daily meals. They grow rapidly, 

 and in most races are dull slaty white in color with a few indis- 

 tinct darker markings. They are very sluggish in habit and 

 can easily be kept in shallow open trays, which should be kept 

 well aired and cleaned. The worms molt every nine or ten 

 days, ceasing to feed for a day before each molting during the 

 forty-five days of larval life. At the end of this time each 

 worm spins a dense white or golden or pale greenish silken 

 cocoon which is, to man, the silk-worm's raison d'etre, but 

 which is primarily the protecting cover for the defenseless pupa. 

 In spinning this cocoon the silken thread, which issues from 

 the mouth and is produced by the hardening of a viscous fluid 

 secreted by a pair of long silk glands stretching far back in 

 the body, is at first attached irregularly to near-by objects, so 

 that a sort of loose net or web is made; then the spinning be- 

 comes more regular, and by the end of three days the thick, 

 firm, symmetrical, closed cocoon, composed of a single con- 

 tinuous silken thread, averaging over 1000 feet long, is com- 

 pleted. Silk growers provide a loose network of branches or 

 wicker on which the silk-worms spin their cocoons. Inside the 

 cocoon the larva pupates, and if undisturbed the chrysalid 

 gives up its damp and crumpled moth after from twelve to 

 fourteen days or longer. A fluid secreted by the moth softens 

 one end of the cocoon so that the delicate creature can force 

 its way out. But this is the happy fate of only those 

 moths which the grower allows to issue to lay eggs for the next 

 year's crop. To produce good silk the grower must save the 



