LIFE OF THE SILKWORM. 9 



length according to temperature, frequency of feeding, race, and the 

 robustness of the worm. The following is about the average: 



First age, from birth to first molt, five to six days. 

 Second age, from first to second molt, four days. 

 Third age, from second to third molt, four to five days. 

 Fourth age, from third to fourth molt, five to seven days. 

 Fifth age, from fourth molt to maturity, seven to twelve days. 



Some time after each molt, perhaps the time needed to regain lost 

 strength and to solidify the newly-formed organs, the worm remains 

 in a state of relative torpor. Not nmch practice is needed to recognize 

 when it has come out of its "sleep." It moves its head and thorax, 

 which are whitish, while the rest of the body is gray, and has com- 

 pletely lost the shining aspect which it had when the worm began to 

 molt. When fairly through its first molt the larva begins again to eat, 

 and its hunger does not cease until it is ready for a new molt. 



Four molts having been made, the worm eats a prodigious quantit}^ of 

 leaf until it reaches its maximum growth, when its appetite diminishes 

 and ceases altogether. It then stops moving and remains for some 

 time in repose, evacuating, meanwhile, its digestive canal, thus losing 

 up to 12 per cent of its weight. Its lean body is now white or yellow, 

 according to the race, and semitransparent. 



Ver}^ soon it begins to move about again, lifts up its head, which is 

 longer and more pointed, and turns in every direction seeking to find 

 a convenient angle, finding which, it throws out a silk thread from its 

 spinneret. First a net is formed to hold the cocoon which is to be 

 spun, then the regular spinning begins and the form of the cocoon is 

 designed. For some time through the veil which very soon is to sur- 

 round it, the diligent larv^a, with its back turned outward, may be seen 

 completing its task. It is calculated that with its head alone the silk- 

 worm makes 69 movements every minute, describing arcs of circles, 

 crossed in the form of the figure 8 (fig. 3, a). 



Meanwhile the web grows closer and the veil thickens, and in about 

 seventy-two hours the worm is completely shut up in its cocoon, which 

 serves it as a protective covering. 



THE CHRYSALIS. 



In the cocoon the silkworm goes through the last phase of its larval 

 life. After four or five days the skin breaks, and the insect which 

 issues from this old covering is the chrysalis, whose weight is often 

 only half that of the larva at its highest development (fig. 3). 



The chrysalis seems to have neither head nor feet, is golden -colored at 

 first, and then turns chestnut brown. The skin dries rapidly and forms 

 a haitl case, on which the lines of only the posterior rings are seen, the 

 place of the first three rings being covered with the wing-cases. 



