1838] 



FARMERS' REGISTER. 



473 



sudden transition from a feeble to a strong degree 

 of heat. It may be said in general, that the too 

 rapid changes from cold to heat, and from heat to 

 cold, are very injurious to them. In theirown coun- 

 try, they arc not exposed to these vicissitudes; 

 therefore they thrive there very well, and do not re- 

 quire the care which we are obliged to give them in 

 our climates, where the temperature ot' the atmo- 

 sphere is so inconstant, that without the help of 

 art we would not be able to have it steady in the 

 laboratories where the silk-worms are led. 



A long course of experience has proved tliat, in 

 France, the 68th degree of heat [indicated by the 

 thermometer of Fahrenheit,] is the most suitable 

 to silkworms. There are some culturists who 

 iiavc pushed the heat to 73, and even to 77 de- 

 grees, and the worms have succeeded equally 

 well. It must be kepc in view that it is not the 

 degree of heat, but the too sudden changes, from 

 one to another, which injure silk-worms. If it 

 happens that it is necessary to hasten the growth 

 of the worms, on account of the advanced state of 

 the leaves, (of which the progress could not be 

 retarded,) it should be done by increasing the 

 heat very gradually, so that the worms will scarcely 

 perceive the changes. For they suffer, it may be 

 said, as much by sudden variations of tempera- 

 ture, as they would by the difHculty of breath- 

 ing, if plunged into nephritic air. 



JM. Boissicrde Sauvages slates that being press- 

 ed by the advanced growth of the leaves, which 

 were well out in the first days of April, he gave 

 to his silk-worms about 100 degrees of heat in the 

 two first days after hatching, and about 95 during 

 the remainder of the first, and through the second 

 age. They took but nine days lor both these 

 ages, or from the hatching to the second moulting 

 inclusively. All the persons who visited the la- 

 boratory supposed that the worms could not but 

 suffer by so great a heat, which produced profuse 

 perspiration in a i'ew minutes after entering the 

 apartment. The walls, and the edges of the hur- 

 dles were so hot that it could not be endured to 

 keep the hand on them. They felt sure that all 

 would perish. Nevertheless, all went on perfectly 

 well, and, to the general astonishment, the crop 

 of silk was abundant. 



He afterwards allowed 93 to 95 degrees of heat 

 for the first age, 89 or 91 for the second; and, 

 what was singular, the duration of the first ages 

 of this raising was nearly as short as the former, 

 of which the worms had much more heat. The 

 cause of this probably is, that there is a limit be- 

 low which the life of the worms cannot be 

 abridged, whatever degree of heat they may be 

 made to bear. It is true that to these had been 

 given, in this raising, and in the ordinary mode of 

 treatment, a like number of repasts. But what is 

 Btill more strange, is, that the worms thus hasten- 

 ed, took but five days for each moulting in the 

 two first following ages, although they were then 

 in a temperature of only 82 degrees; while worms 

 which have not been, from the commencement, 

 pushed forward in the same manner, require, at 

 the same heat, seven to eight days for each of 

 these same ages, that is to say, for" the third and 

 Iburth. It seems as if it were sufficient to have 

 put these little animals in the proper train, for 

 them to obey the first impulse, or the first bend 

 given to them. This early high degree of heat, 

 ae given in this case, which produces a rapid 

 Vol. VI.— 60 



growth, gives the worms, at the same time, a vi- 

 gor and activity which they carry info their fol- 

 lowing ages; and this is an advantage in the has- 

 tened rearing, (that is, pushed forward by heat,) 

 and which, besides, prevents many maladies. 

 This hastened management abridges the trouble 

 and the labor, and releases the manager sooner 

 from the inquietude and sense of insecurity which 

 he will always leel until the cocoons are com- 

 pleted, and gathered. 



To pursue this method of using high tempera- 

 ture, it is necessary to pay the utmost attention to 

 the seasons' being more or less advanced, and to 

 the state of growth of the leaves, and that there 

 is no danger of that growth being afterwards 

 checked by cold. On the other hand, if the put- 

 ting forth of the leaves is backward, and it is Ibl- 

 low^ed by heat which lasts long, as may usually 

 be expected, and yet if but little heat is kept up in 

 the laboratory, the worms will advance slowly, 

 and their growth will be prolonged. Still the 

 leaves grow and become harder, and have too 

 much consistence for the worms in their backward 

 state. This then is a state of things in which the 

 growth of the worms should be hastened by con- 

 tinued higher temperature, in order that their pro- 

 gress may be brought up to that of the growth 

 of the leaves, which is an essential point. 



If a culturist should determine early to pursue 

 this method, he should set and hatch his eggs 

 some days later than the others. For a still 

 greater degree of prudence, he will wait eight 

 days, and will calculate afterwards the duration of 

 the ages; or rather, he will do better to so arrange 

 his procedure as to have the latest feeding of the 

 worms to correspond in time with the state of full 

 growth of the leaves.* 



It has been said above that the worms produced 

 from an ounce of eggs, ought to occupy., in their 

 first age, and to the first moulting, a space of 7 or 

 8 square feet; of 14 or 15 to the second moulting; 

 of 30 to 35 until the third; and for the fourth and 

 last, the space ought to be at least 83 or 84 square 

 feet. It is also necessary, in fixing the proportion 

 of the quantities ol' food, given to the worms, to 

 the spaces allowed, not to forget, that until the 

 first moulting the temperature must be constantly 

 maintained at 75 degrees; in the second age it 

 will descend to 73; in the third, the temperature 

 should be from 73 to 71; and from 71 to 68 de- 

 grees in the fourth age. These degrees of heat 

 being well established, there should be given to 



* This new mode of rearing worms under an unu- 

 sual and very high temperature, if sufficiently tested 

 by experience, would be a far more valuable improve- 

 ment in practice in Virginia, and the more southern 

 states, than in France. For, one of the greatest dan- 

 gers which threatens silk-worms here, is the circum- 

 stance of the heat of the weather occasionally rising 

 so much higher than the proper temperature for the 

 interior of the laboratory, that the latter could not be 

 kept down by shading and ventilation. This evil 

 would sometimes happen to the earliest broods; and 

 would certainly attend serond or third broods, reared 

 in midsummer, if the usual degrees of temperature 

 directed above, were attempted to be preserved, or if 

 no artificial mode of heating were put in use. This 

 new mode of using great heat would be an admirable 

 and sufficient safeguard against this otherwise certaio 

 and great evil; as the heat used would rarely be ex« 

 ceeded by the natural heat of our hottest days.-.- 

 Tbanslator. 



