274 INSECT ARCPIITECTURE. 



day after liatcliing, the second begins on the eighth day, 

 the third takes np the thirteenth and fourteenth days, and 

 the last occurs on the twenty-second and twenty-third days. 

 The fifth age, in such cases, lasts ten .days, at the end of 

 which, or thirty-two days after hatching, the caterpillars 

 attain their full growth, and ought to be three inches in 

 length ; but if they have not been properly fed, they will 

 not be so long. 



With the age of the caterpillar, its appetite increases, 

 and is at its maximum after the fourth moulting, w^hen 

 it also attains its greatest size. The silk gum is then 

 elaborated in the reservoirs, while the caterpillar ceases to 

 eat, and soon diminishes again in size and weight. This 

 usually requires a period of nine or ten days, commencing 

 from the fourth moulting, after which it begins to spin its 

 shroud of silk. In this operation it proceeds with the 

 greatest caution, looking carefully for a spot in which it 

 may be most secure from interruption. 



" We usually," says the Abbe de la Pluche, " give it 

 some little stalks of broom, heath, or a piece of paper 

 rolled up, into which it retires, and begins to move its 

 head to different places, in order to fasten its thread on 

 every side. All this work, though it looks to a b^^stander 

 like confusion, is not w^ithout design. The caterpillar 

 neither arranges its threads nor disposes one over another, 

 but contents itself with distending a sort of cotton or floss 

 to keep off the rain ; for Nature having ordained silk-worms 

 to work under trees, they never change their method even 

 when they are reared in our houses. 



" When my curiosity led me to know how they spun 

 and placed their beautiful silk, I took oiie of them, and 

 frequently removed the floss with which it first attempted 

 to make itself a covering; and as by this means I 

 weakened it exceedingly, when it at last became tired of 

 beginning anew, it fastened its threads on the first thing 

 it encountered, and began to spin ver}' regularly in my 

 presence, bending its head up and down, and crossing to 

 every side. It soon confined its movements to a veiy 

 contracted space, and, b}^ degrees, entirely surrounded 



