28 MONTHLY JOURNAL OF AGRICULTURE. 



things, which the student of Natural History has so many opportiimties of contemplating with 

 delight aiul ailiniration. 



In about eight days from its being hatched, its hea<l becomes perceptibly larger, and the 

 wonn is attacked by its first sickness. This lasts for three days ; dui-ing which time it re- 

 I'uses food, and remains motionless as in a kind of lediargy. Some have ihou^dit this to be 

 tileep, but the fatal teiTniuation which so tiequenlly attends these sicknesses seems to atford 

 a denial to this hypothesis. The silk-worm increases its size so considerable, ;tnd in so short 

 a space of time, — its weight being multiplied many thousand fold in the c<jin-se of one month, 

 — that if only one skin had been assigned to it, which would serve for its whole caterpillai' 

 state, it would with difficulty have distended itself sufficiently to keep pace with the insect's 

 growth. The economy of Nature has tlierefore atlmirably provided the embryos of other 

 skins, destined to be successively called into iLse ; and this sickness of the wonn, ajid its dis- 

 incUnation {(>r Ibod, may very probably be occasioned by the pressm-e of the skm, now be- 

 come too sm;Jl for the body which it encases. 



At the end of the tliird day from its first refusal of food, the animal appears, on that account 

 much wasted in its bodily frame ; a circimistance wliich materially assists in the painful oper- 

 ation of casting its skin : this it now proceeds to accomplish. To facilitate tliis moultiug, a 

 sort of humor is throw^n off by the wonn, which spreading between its body and the skin 

 about to be abandoned, lubricates their surfaces, and causes them to separate the more readi- 

 ly. The insect also emits fi-om its body silken traces, wliich, adhering to the spot where it 

 rests, serve to confine the skin to its then existing position. These preliminaiy steps seem to 

 call lor some considerable exertion, as after them the worm remains quiet tor a shoit space of 

 time, to recover from its fatigue. It then proceeds, by nibbing its head among the leaty fibres 

 suiTounding it, to disencumber itself of the scaly covering. Its next effort is to break through 

 the skin nearest to the head, wliich, as it is there the smallest, calls for the gi-eatest exeition ; 

 and no sooner is this accomplished and the two front legs are disengaged, than the renuunder 

 of the body is qiuckly drawn forth, the skin being stUl fastened to the spot in the manner 

 alre;uiy described. 



This moulting is so complete, that not only is the whole covering of the body cast off, btd 

 that of the feet, the entire skull, and even the jaios, including the teeth. These several parts 

 may be discerned by the unassisted eye ; but become \ery ajipai'ent when viewed tln-ough a 

 magnifying lens of moderate power. 



In two or three minutes from the beginning of its efforts the wonn is wholly heed, and 

 again puts on the appearance of health and vigor ; feeding with recniited appetite upon its 

 leafy ban<]uet. It sometimes happens that the outer skin refuses to detach itself wholly, but 

 breaks and leaves lui annular portion adhering to the extiemity of liis body, from which all the 

 sDniggles of the insect c;ninot wholly disengage it. The pressure thus occasioned induces 

 swelling and uifiauimation in other parts ol" the body ; and, after efforts of greater or less dura- 

 tion, death generally terminates its suffering. 



Wonns newly freed from their exuviaj are easily distinguished from others by the pale color 

 and wrinkled appeai-ance of their new skin. Tliis latter quality, however, soon disappears, 

 through the repletion and growth of the insect, which continues to feed during five days. At 

 this time its length will be increased to half an inch ; when it is attacked by a second 

 sickness, followed by a second moulting, the manner of peri()nning which is exactly similar 

 to the fonner. Its appetite then again returns, and is hidiilged other five days, in the course of 

 which time its length increases to three-quarters of an inch : it then imdergoes its thiid sick- 

 ness and moulting. These being passed in all respects like the fonner, and five more days 

 of feed havhig followed, it is seized by its fourth sickness, and casts its skin for the last time in 

 the catei-pillar state. The worm is now about one and a half or two inches long. This last 

 change being finished, the womi devom's its food most voraciously, and increases rapidly in 

 size during t«n days. 



The silk-wonn has now attained to its full growth, and is a sleiid(>r cateqiillar fi-om tv\o and 

 a half to three inches in length. (Seel'late, Fig. 1.) The peculiarities of its stnicture maybe 

 better examined now than in its earlier ages. It c:m readily be seen that the wonn has twelve 

 membraneous rings round its body, parallel to each other ; and which, ;uiswering to the move- 

 ments of the animal, mutually contract and elongate. It has sixteen legs, in pairs : six in front, 

 which are covered with a sort of sliell or scale, and are placed un(l(M- the tluee fii-st rings, and 

 cannot be either sensibly leuglliened, or their position altered. The other ten legs lue called 

 holders: these are menibnuieous, flexible, smd attached to the body under the longs. bemg 

 furnished with litde hooks, which assist the insect hi climbing. The skull is enclosed in a scaly 

 substance, similar to tlie covering of the first six Icl's. The jaws arc hidented or sen-ated like 

 the t<'eth of a saw, an<l llieir strength is great, considering the size of the insect. Its mouth is 

 peculiar, having a vertical instead of an horizontal aperture ; and the wonn is fiiniL-shed with 

 eighteen breathing holes, placed at equal distances down the body, nine on each 

 side. Each ot these holes is supposed to be the tennination of a particular org;ui of 

 respiration. On either sideof the head, near to the mouth, seven small eyes may be dis- 

 cerned. The two bro;ul a[)pi-:u-,uices liigher upon the head, which are fre<]ucntly mistaken 

 for eyes, are bones of the skull. The two apertures through which the wonn draws its 

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