HISTORY AND HABITS OF THE SILK-WORM. 29 



silkfn filamimt are placed just beneath the jaw, and close to each other ; these beuig exceed- 

 ingly luiiiiite. 



At till' [)(;nn;l above-mentioned the desire of the wonn for food beprius to abate : the first 

 symptom of this is the appearance of the leaves nibliled into small portions and wasted. It 

 soon afler entirely ceases oven to touch the leaves ; appears restless and uneasy; erect« its 

 head ; and moves about from side to side, with a circular motion, in quest of a place whereia 

 it can commence its labor of si>inuing. Its color is now light green, with some mixture of a 

 darker hue. In tweuty-four hour.s from the time of its abstaining from food, the mateiial for 

 forming its sUk will be digested in its reservoirs ; its green color will disapjiear ; its body 

 will have acquired a degree of glo.-isness, and have become j)artia!ly iransjiarcut toward its 

 neck. Before the worm is quite prepared to s()in, its body will have acquired greater iirrn- 

 ■ness, and be in a trilling measure lessened in size. 



" The SLd)sUuice," saj-s Mr. Porter, " of which the silk is composed, is secreted in thcj'orvt, 

 of a fine yellow transparent gttm in two separate vessels of slender dimensions, wound, as it 

 were, o-n two spindles in the stomach; and if unfolded, these vessels would be about ten in- 

 ches in length."* This stjitement Ls proved to be eiToneous, as the reader will perceive, at 

 the couclvisioii of this chajjter. 



When the wonn has fixed npon some angle, or hollow place, whose dimensions agree wifJi 

 the size of its intended silken ball or cocoon, it begins its labor by throwing forth thin and ir- 

 regular threads, (!?eo Plate, Fig. 2.) wliich are intended to support its future dwelling. 



Dunns the first day, the iiis(!ct foniis uponsthesea loose stviictme of an oval shape, which 

 is called Hoss silk, and within which covering, in the three following days, it forms the firm 

 and consistent yellow ball ; the laborer, of com'se, always remaining on the inside of the 

 siihere which it is fonniug.t 



The silken fihmient. which wlien drawn out appears to be one thread, is composed of two 

 fibr(\*, unwound througli tlie two orifices before described ; and these fibres are brought to- 

 gether by means of two hoaks, placed within the silk -worm's mouth for the purpose. The 

 wonn rests on its lower e.xtreinity throughout the unwinduig operation, and employs its 

 mouth and fitnit legs m the task of directing and uniting the two filaments. The lilament is 

 not w-ound iu regular concentiic cu'cles round the ulterior surface of the ball, but in spots, 

 going backvvTard and forward with a sort of wavy motion. This apparently iiregiilar manner 

 of proceeding is phunly perceptible when the silk is being reeled off the ball ; which does not 

 make more than one or two eutu'e revolutions while ten or twelve yards of silk are being 

 ti'ansfened to the recl.t 



At the end of the third or fourth day, the worm will have completed its task ; and we have 

 then a silk cocoon, (See Plate, Fig. 3.) with the worm imprisoned in its center ; the cocooa be- 

 ing from nn inch to an inch and half long, and of a yellow or oraiige color. 



Wlien the insect has linislied its Uibor of unwinding, it smears the entire internal surface 

 of tlie cocoon with a peculiar kind of gum, very similar in its nature to the matter which 

 fonns the .silk itself; and this is no doubt designed as a shield against rain or the humidity of 

 the atmosphere, for the clirysalis in its natural state ; when of course it wowld be subject 

 to all varieties of weather. The silken filament of which the ball is made up. is like\\'ise ac- 

 compmiied, througliout its entire length, by a portion of gum, which serves to give finimess 

 and consistency to its texture ; and assists in rendering the dwelling of the chrysalis imper- 

 vious to moisture. This office it perfonns so well that when, for the pur])ose of reeling the 

 silk with gi'eater facility, tlie balls are tlirown into basins of hot water, they swim on the fop 

 with all the buoyancy of i)ladders ; nor, imle.«s thebaU be imperfectly fonned, does the water 

 peneti-ate within until the silk is nearly all unwound. In the Plate, Figure 4, the cocoons 

 are cfi-awu two-tliirds of the usual size, and are shown with pai-t of the outward floss siUc re- 

 moved. 



The continual emission of the silken material during the formation of ite envelop, together 

 Avith its ir.itiu'cd evaporation, micompensated by food, causes the wonn gradually to contract 



• Porter's " Treatise on the Silk Manufacture," p. 111. 



t If at this time any of the threads intended for the support of the cocoon should be broken, the worm 

 will tind, in the pioi-ress of its work, that the bull, not bein;; properly poised, becomes unsteady, so that the 

 inscLt is uniJ)le properly to go forward with its Ial)ors. Under tlnse circumstances the worm pierces and 

 altogether quits the unfinished coeoon, and throws out its remaining threads at random wherever it pawses ; 

 by which means the silk is wholly lost, and the worm, finding no place wherein to prepare for its change, 

 dies wilhout having eft'ected it. It may sometimes happen, but such a tiling is of unfrequent occurrence, 

 that the preparatory threads before-mentioned are broken by another worm working in the neighborhood, 

 when tite same unaatisfactory result will be experienced. 



[Obs. on the Culture of SUk, by A, Stevbnson. 



J Mr Robinct, of Paris, made the following curious calculation on the movements a silk-worm must 

 make in fonn.ng a coceon supposed to contain a thread of l.jOO metres. It is known, says Mr. Robinet, that 

 the silk-worm, in forming his cocoon, does not sp;« the silken filament in concentric circles round the in- 

 terior surface of the ball, but in a zigzag manner. This it etiects by the motions of its head. Now if each 

 one of the^e motions gives half a centimetre of tlie silken filament, it follows that the wor.n must m.'Jie 

 aoO.OCO motions of its head to fonn it: and if the labor requires 72 hours in 'he performance, the crealUPB 

 mokes lOO.OtX," mntiona every 24 hours, 4,166 per hour, 69 per minute, and a little more thau one in a 

 eucoud ! 



