30 



MONTHLY JOURNAL OF AGRICULTURE. 



in bulk ; it becomes wrinkled, anJ tlie rings of its body approach nearer to each other and 

 appear more decidedly marked. ^Vh^n the b;ill is finished, the insect rests awhile Irom its 

 toil, and then throws off its cateqiillar garb. If the cocoon be now opened, its inhabitant 

 will appeal' in the fonn of a cliiysalis or am-elia, in shape somewhat resembling a kidney- 

 bean (See Plate, P'igiire 5,) but pointed at one end, having a smooth Iji-own skin. Its 

 former covering, so dissimilar to the one now assumed, will be fbmid lying beside it. 



The accoinit which h;is been given of tlie progressions of the silk-vvomv shows that, in 

 its vaiious moditications, the aiiimnl organization of the insect has been always lending to- 

 ward its sim.plificalion. Count Dandolo, wn-iting ui)on this subject, observes, " Thus the 

 caterpillar is in the first instance composed of animal, sUky, and excremental particles ; this 

 forms the state of the o-vci7f/;io' caterpillar: in the next stage it is composed of anim;d and 

 silky particles ; it is then the mature caterpillar : and las ly, it is reduced to the animal par- 

 ticles alone ; and is termed in tliis state the chrysalis. The jioet Cowper, in the foOowing 

 lines, beautifully illustrates this subject : 



The beams of April, ere it goes, 



A worm, scarce visible, disclose ; 



All winter lons^ content to dwell 



The tenant of his native shell. 



The same prolific season gives 



The sustenance by which he lives, 



The mulberry leaf, a simple store. 



That .serves him — till he needs no more ! 



For, his dimensions once complete, 



Thenceforth none ever sees him eat : 



Though till his growing time be past 



Scarce ever is he seen to fast. 



That hour arrived, his work begins ; 



He spins and weaves, and weaves and 



spins ; 

 Till circle upon circle, wound 



Careless around him and around, 



Conceals him with a veil, though slight, 



Impervious lo the keenest sight. 



Thus .self enclosed, as in a cask, 



At length he finishes his task : 



And, though a worm v^hen he was lost. 



Or caterpillar at the mo.st. 



When next we see him, wings be wears, 



And in papilio pomp appears ; 



Becomes oviparous ; supplies 



^Vith future worms and future flies 



The next ensuing year — and dies! 



Well were it for the world if all 



Who creep about this earthly ball, 



Tliough shorter-lived than most he be, 



Were useful in their kind as he. 



It has been already noticed that the pi-ogressious of the bisects ai-e accelerated by an in- 

 crease of temperature ; and some vmiation will equally be experienced where different 

 modes of treatment are followed ; and, in pai-ticular, where different periods of the year are 

 r.liosen in which to produce and real" the worm. Malpighius, in his " Anatomy of the Silk 

 Worm," says, that wonns \Ahii:h he hatched in May were eleven days old ere they were at- 

 tacked by their first sickness ; others hatched in July were ten days, and those brought forth ^ 

 in August nine days, before they refiised theii- food, prepm-atoi-y to their first moulting. 

 Eight days appear to be the most usual tenn for their first attack ; and Viy his judi- 

 cious treatment Count Dandolo shortened even tliis tenn by two days. In Europe, ex- 

 cept where recom-se is had to aitificitd aid, tlie tenn of the caterjiiUar stitte is usually that 

 v^'liich has been already mentioned. 



Sudden tnmsitions tiom cold to heat, or vice versa, are highly injuriotis to the silk-worm ; 

 Imt it cMi bear a veiy high degi-ec of heat, if uniformly maintained, without sustaining inju- 

 ry. Count Dandolo (jl)S(n-\-ed, that " the greater the degree of heat in whith it is reared, the 

 more actite an; its wants, the more rapid its pleasures, and the shorter its existence." Mon- 

 sieur Boissier de Sauvagues made many experiments on this jioint. One year, ■when by the 

 early appearance of the mulbeny leaves, which were developed by tlie end of April, he was 

 iorced to huny forward the operations of his filature, he raised the heat of tlie ;!p:u tni"nl in 

 which the newly halclied worms were jjlaced to 100° ; gradiudly diiniuishinu this during 

 their first and .second ages to !).">°. In consequence of the animal excitement thus induced, 

 there elapsed only nine days between the hatcliing and the second moulting inclusively. It 

 was the general opiinon of those ctdtivators who witnessed the exi)eriinent, that the insects 

 would iK>t be able to exist in so intcnisely heated an atmosphere. The walls of tlie apart- 

 ment, and the wicker hurdles on which tlie worms were placed, cotdd scarcely be toucluxl 

 from the gieat heal, and yet all the changes and progressions went tbrward perfecdy well, 

 !Ui(l a most aliuiidant cro[) of silk was tin- result. 



The same gi-ntlemaii, u\\ a sulKcciuent occasion, exposed his brood to the temperature of 

 93" to O-j" during their first age ; of 89° to 91^ in the second age ; and remarked that the 

 attendant circumstances were the same as in his foniier experhnent, the changes of the worm 

 being ])erfi>rmed in the same space of time ; whence he came to the conclusinn, that it is not 

 .practicable to accelerate their progress beyond a certfiin point by any suiieiadditlons oi heat. 

 In both of these experiments the ((uantity of food consumed was as great as is usually given 

 during the longer ])criod employed in ilie common manner of rearing. After the .second 

 moulting had taken ])lace in the last experiment, the temperature was k)wered to 82° ; and 

 it is remarkable that the wonns occupied only five days in completing Uieir third and fourth 

 changes, althougli others which had been accust(uned to tliis U)wer degree from their hiith 

 micupied seven or eight davs for each of tliest; moultings. It would theref(>i'e seem that the 

 constitution of the insects ciui be atl'ected, and lui impetus given to their functions at ih© 



