HISTORY AND HABITS OF THE SlLK-WORiM. 31 



period of their first animation, which accompiinies them tyjLrough their after stages. So fitr 

 from this forcing system proving injurious to iho lii^ahh of siik-wonns, M. do Siiuvagues 

 found tlint his broods were unusually hoaUhy ; and liiat wliile tiie lahors of cultivation were 

 abridged in their duratinii, mucii of the altoiidaut au.viety was removed. 



Like other caterpillars, the silk wonii is not a Wiuuii-blooded animal, and its temperature 

 is therefore always equal to tint of llie atiiios])iiere in which it is placed. In the silk-prf>- 

 duchig counti-ies, where modes of iU'titicial heating have not been studied practically ;uid 

 scieutificallv, the dilHculty mid expense that must attend the prosecution of this heat 

 ing system, form abundant reiisons why it cannot be generally adopted. The great suscepti- 

 bihty of the insect to atmospheiic influences would also in a great degi-ee render unsuitable 

 the more connnon arrangements for the purpose. The plan of warming apartnu-nts by means 

 of stoves, in its p.issage thi-ough which the air becomes highly heated betiire it mi.xes with 

 and raises the general tem[)erature of the ;iir in tlie chamber, is liable to this inc<Jiivenience — 

 that the portion so introduced, having its vital property impaired by the bimiing he;it through 

 which it has passed, injures propoitionably the respirable quality of tiie whole atmosphere ; 

 an effect which is easily perceptible l)y tlmsc^ who inhale it. A better plan of heating has 

 lately been suggested, and is ra[)idly coming into jiractice, viz., of wanning buildings by a 

 current of hot water (an American niventiou.) winch is, by a very simple process, kept con- 

 stantly flowing in close chrmnels through the apartment, where it continually gives (iff ha heat 

 by raiUation ; and the degree of tliis being far below the point which is injurious to the vital 

 quality of air, the evil bf^tbre idluded to is avoided. If the expense of fiiel be not Um great, 

 as compiired with that of the labor which would be .sav(Ml by this invention, the adoption in 

 silk countries of" sucli a mode of raisuig and regulating the temperature might, probably, prove 

 a<lv;uitiigeous. 



The silk-wonn remains in the fonn of a chiysalis for periofis wliich, according to the 

 cliin:ite or the temperature wherein it may be placed, vary from fifteen to thirty days. In 

 India, the time is much shorter ; in Spain and Italy, eighteen to twenty days. In France 

 three weeks ; and in the climate of England, when unaccelerated by lutificial means, thirty 

 days will elapse fi-om the time the insect begins to spin until it emerges in its lait and per- 

 fect fonn. It then throws off the shroud which hsul confined it in seeming l/felcssness, and 

 appears as a large moth of a grayish-white color, furnished with four wings, two eyes, and 

 two black horns or antlers wliich present a feathery appearance (See I'late, Fig. 6.). 



If left until this period witliui the cocoon, the moth takes miinediate measures for its ex- 

 trication : ejecting from its mouth a liquor with which it moistens and lessens the adhesive- 

 ness of thrj gura wherewith it had lined the interior surfiice of its dwelling, and the insect is 

 enabled, by ti'equeut motions of its head, to loosen without breaking, the texture of the ball ; 

 then using its hooked feet, it jtushes aside the filament^s mid makes a passage for itself into light 

 and freedom. It is eiToneously said that the moth recovers its libertv' by gnav^-ing the silken 

 threads ; but it is found, on the conti-ary, that if carefiilly unwound, tlieir continuity is by tloia 

 means rarely broken. 



One of the most remarkable circumstiinces connected with the Natund Historv of silk- 

 worms, is the degree in which their bulk and weight are increased, and the limited time 

 wherein that increase is attained. Coiuit Daudolo, who appears to have neglect'-d nothing 

 that could tend to the right understmding of the subject, and to the consetjuent iinprovemeiit 

 of the processes employed, had patience enough to count and weigh many hundred thousand 

 eggs, as well as well as follow out to the ultimate result Ins uiquiries respecting their pro- 

 duce. He found that on an average sixty-eiijht sound silk-woniis' eggs weighed one grain. 

 One ounce,* therefore, comprised, n9,l()8 eggs. But one-twelfth part of this weiirht evapo- 

 rates previous to hatching, ;uid the shells are eijual to one-fifth more. If, therefore;, from one 

 ounce, composed of .576 gniins, 48 grains be deducted for evaporation, and 11^ for tiie shells, 

 413 gi-ains will renuiiu, equal to the weight of3n,lt)a young wonns ; and at this late, .54,.0'26 

 of the insects when newly hatched, are reciuired to make up the ounce. After the firet cast- 

 ing of the .skin, 3,840 worms are found to have this weight, so that the bulk and weight of 

 the insects have in a few days been multiplied more \h.ui fun rtce?i (iines. After the second 

 change GIO wonns weigh an ounce, tlu-ir weight b^'ing increased in the intennediate time six 

 lijld. In the week passed between the second and third ages, the iiumb<;r of insects required 

 toimike up the same weight, decreases from (jlO to 144, their weight being therefore more 

 th:m quadnipled. During the fourth age, a similar nite f)f increase is maintained : thirty-five 

 worms now weigh an ounce. The fifth age of the cateqiillar compiises nearly a third part 

 of its brief existence, and has been descril)ed, by an euthusia.stic writer on the subject, as the 

 happiest period of its life, during which it nipidly increases in size, i)r<;parini: and secreting 

 the material it is about to spin. When the silk-wonns are fully grovvii, and have anived at 

 their period of finidly rejecting food, six of them make up the weight of an ounce. They hiive, 

 therefore, since their last change, again a<lded to then- weight sixfold. 



It is thus seen that, ui a few short w-eeks, the insect has multiplied its weight more than' 



* This ounce contains 576 ^^rains ; 8..J.12.') of these grains equal seven grains troy. One ounce avoirdu- 

 pois is therefore equal to about 53.3 grains, and between H-12 and 11-13 ounce avoirdupois equals one of 

 the above ounces. 

 (79) 



