112 NATURAL HISTORY READER. 



sixth of an inch. To finish his task in the seventy-two 

 hours requires about three hundred thousand motions in a 

 day, or sixty-nine every minute. No weaver can equal this 

 in activity for a single hour, and much less would any one 

 be able to keep up to the highest rate of speed for three 

 days in succession. 



(J. The silk-worm lias now changed from the larva to 

 the pupa state. After finishing his cocoon he becomes 

 torpid once more. His body is inclosed in a kind of shell, 

 the color of which is a golden yellow. A very slight move- 

 ment of the posterior part, which requires the closest at- 

 tention to observe, is the only sign of life. Yet, within, a 

 most remarkable change is taking place, and in about fif- 

 teen days is complete. The shell of the pupa now splits 

 open, as did the skin of the larva, and there emerges a 

 complete butterfly — a creature as unlike the forms through 

 which it has already passed as can well be imagined. 



7. This butterfly is almost an inch long and two inches 

 across when its wings are spread. It is of a whitish or 

 pale yellow color. Sex in the silk-worm is developed only 

 in the butterfly form. The male flies about chiefly in the 

 evening, but the females have but little activity. In three 

 days the female deposits about five hundred eggs, and as 

 her work is ended she immediately dies ; the life of the 

 male has about the same duration. 



8. When the cocoons are spun they are separated into 

 two parts — those which are to be wound, and those which 

 are reserved for hatching the butterflies from which the 

 new supply of eggs is to lie obtained. The former are 

 placed in hot water, which kills the pupa within, and the 

 silk is wound off from the outside. 



9. Such is a brief history of the life of an insect which 

 forms the basis of one of the greatest industries of the 

 world. Silk-making probably originated in China, and is 

 now extensively carried on in that country and in Japan. 



