SILK-PRODUCING INSECTS. 21 



tunately they cease eating and become drowsy as 

 the time of moulting approaches. At all times 

 their greatest enemies are damp and noise ; they 

 must be kept quiet, and, above all things, clean. 



The larvas born from one ounce of eggs require 

 during their first age, which lasts five days, about 

 7 Ibs. weight of mulberry leaves. After the first 

 moulting, and during the second age, which lasts 

 only four days, they require 21 Ibs. of leaf. During 

 the third stage, which lasts a week, they devour 

 70 Ibs. of mulberry leaf; in the fourth stage (also 

 a week), 210 Ibs. ; and during the fifth stage, from 

 1200 to 1300 Ibs. of leaf. On the sixth day of this 

 last period, they devour as much as 200 Ibs. weight 

 of leaf, with a noise resembling the fall of a heavy 

 shower of rain. On the tenth day they cease eating, 

 and are about to undergo their first metamor- 

 phosis.* 



At this period of their lives they begin to spin 

 their cocoons. The silkworm spins on an average 



* Although the larvce or grubs of insects in general are very 

 voracious, as in the example before us, the perfect insect, on the 

 contrary, can li ve for a long time without food. Thus, Mr. .Baker 

 has proved that the beetle called Slaps mortisaga can live for three 

 years without food of any kind. The little sugar fish (Lepisma 

 saccharina) was shut up in a pill box by Mr. Stephens, in 1831, 

 and found alive in 1833. Leuwenhoek saw a mite which was 

 gummed alive to the point of a needle, live for eleven weeks in that 

 position. Other examples have been noticed in Kirby and Spence's 

 admirable " Introduction to Entomology," 



