798 



A HISTORY OF 



served, contribute greatly to their health and 

 increase. 



The worm, at the time it bursts the shell, is 

 extremely small, and of a black colour ; but 

 the head is of a more shining black than the 

 rest of the body : some days after, they begin 

 to turn whitish, or of an ash-coloured gray. 

 After rhe skin begins to grow too rigid, or the 

 animal is stinted within it, the insect throws 

 it off, and appears clothed anew : it then be- 

 comes larger, and much whiter, though it has 

 a greenish cast ; after some days, which are 

 more or less, according to the different heat of 

 the climate, or to the quality of the food, it 

 leaves off eating, and seems to sleep for two 

 days together : then it begins to stir, and put 

 itself into violent motions, till the skin falls off 

 the second time, and is thrown aside by the 

 animal's feet. All these changes are made in 

 three weeks or a month's time ; after which 

 it begins to feed once more, still in its cater- 

 pillar form, but a good deal differing from it- 

 self before its change, In a few days' time it 

 seems to sleep again ; and, when it awakes, it 

 again changes its clothing, and continues feed- 

 ing as before. When it has thus taken a suf- 

 ficiency of food, and its parts are disposed for 

 assuming the aurelia form, the animal forsakes, 

 for the last time, all food and society, and pre- 

 pares itself a retreat to defend it from external 

 injuries, while it is seemingly deprived of life 

 and motion. 



This retreat is no other than its cone, or 

 ball of silk, which nature has taught it to com- 

 pose with great art; and within which it 

 buries itself, till it assumes its winged form. 

 This cone or ball is spun from too little long- 

 ish kinds of bags that lie above the intestines, 

 and are filled with a gummy fluid, of a mari- 

 gold colour. This is the substance of which 

 the threads are formed ; and the little animal 

 is furnished with a surprising apparatus for 

 spinning it to the degree of fineness which its 

 occasions may require. This instrument in 

 some measure resembles a wire-drawer's 

 machine, in which gold or silver threads are 

 drawn to any degree of minuteness ; and 

 through this the animal draws its thread with 

 great assiduity. As every thread proceeds 

 from two gum-bags, it is probable that each 

 applies Us own ; which, however, are united, 

 as they proceed from the animal's body. If 

 we examine the thread with a microscope, it 



will be found that it is flatted on one side* 

 and grooved along its length : from hence we 

 may infer, that it is doubled just upon leaving 

 the body ; and that the two threads stick to 

 each other by that gummy quality of which 

 they are possessed. Previous to spinning its 

 web, the silkworm seeks out some convenient 

 place to erect its cell, without any obstruction. 

 When it has found a leaf, or a chink fitted to 

 its purpose, it begins to wreath its head in 

 every direction, and fastens its thread on every 

 side to the sides of its retreat. Though all its 

 first essays seem perfectly confused, yet they 

 are not altogether without design : there ap- 

 pears, indeed, no order or contrivance in the 

 disposal of its first threads : they are by no 

 means laid artfully over each other, but arc 

 thrown out at random, to serve as an exter- 

 nal shelter against rain ; for nature having 

 appointed the animal to work upon trees in 

 the open air, its habits remain, though it is 

 brought up in a warm apartment. 



Malpighi pretends to have observed six dif- 

 ferent layers in a single cone of silk ; but 

 what may easily be observed is, that it is com- 

 posed externally of a kind of rough cotton- 

 like substance, which is called floss ; within, 

 the thread is more distinct and even ; and 

 next the body of the aurelia, the apartment 

 seems lined with a substance of the hardness 

 of paper, but of a much stronger consistence. 

 It must not be supposed, that the thread which 

 goes to compose the cone, is rolled round, as 

 we roll a bottom ; on the contrary, it lies upon 

 it in a very irregular manner, and winds off 

 now from one side of the cone, and then from 

 the other. This whole thread, if measured, 

 will be found about three hundred yards long ; 

 and so very fine, that eight or ten of them are 

 generally rolled off into one by the manufac- 

 turers. The cone, when completed, is in form 

 like a pigeon's egg, and more pointed at one 

 end than the other: at the smaller end, the 

 head of the aurelia is generally found ; and 

 this is the place that the insect, when con- 

 vrrted into a moth, is generally seen to burst 

 through. 



It is generally a fortnight or three weeks 

 before the aurelia is changed into a moth ; 

 but no sooner is the winged insect completely 

 formed, than having divested itself of its 

 aurelia skin, it prepares to burst through its 

 cone, or outward prison s for this purpose it 



