133 [ 175 3 



VIII. Diseases from sudden chans:es of temperature. 



The great importance of preserving silkworms uniformly in that 

 particular degree of heat which ample experience has proved to bft 

 most proper for each particular stage of their short existence, has been 

 fully pointed out in the course of the instructions for rearing them; 

 and as no cause will more certainly produce disease, than inattention 

 to this point, it is proper to notice it in this place. To ensure regular 

 growth to the worms, and the gradual evolution of their fine organs, 

 it is essential to protect them against sudden changes of temperature, 

 which often amount to 40°, in the United States, in the course of twen- 

 ty-four hours. Hence it is absolutely necessary to regulate the heat 

 of the apartment by a thermometer, and to warm it by means of a 

 stove of brick, tile, or porcelain, in preference to one of iron; be- 

 cause the heat communicated by any of the three first, will be mucli 

 longer uniform, than when one of the last is used. The tender na- 

 ture of the insect causes it to be extremely sensible to a diminution of 

 temperature, and when this takes place, to the extent of several de- 

 grees, they become chilled and torpid, they cease to eat, the digestion 

 of their food is interrupted, their growth is checked, and the founda- 

 tion of disease is laid. 



Again, danger to their health will arise from an incautious increase 

 of heat, after being thus chilled; and exposure to sudden and great 

 heat, when near the time of spinning, will cause silkworms to cease 

 eating, to become enfeebled and relaxed, and sometimes to die. The 

 Abbe Sauvage* particularly notices the danger to their health from 

 this cause. In the summer of 1825, vast numbers were killed from 

 it, in Mansfield, Connecticut.! 



PARTICULAR DISEASES OF SILKWORMS. 



The Passis. — This disease appears after the first moulting, where 

 the worms advance unequally in growth; they are observed to be 

 short, thin, and without vigor or appetite: it is ascribed to their being 

 too much heated in their early state. The remedies consist in sepa- 

 rating them from the healthy worms, putting them in another apart- 

 ment which is well ventilated, giving them tender leaves, and in pre- 

 serving them in a uniform temperature, which ought to be a little 

 higher than that in which the healthy ones are kept; for although heat^ 

 unduly applied, was one cause of their disease, yet, when feeble, they 

 require more warmth than healthy worms to restore their vigor. 



The Grasserie. — This appears towards the second moulting, and iij 

 the third or fourth ages. It is ascribed to the food being too substan- 

 tial or nourishing for the young worms. They eat, but they do not 

 digest their food: hence they swell, their bodies become opaa^ and 

 of a green color, and their skins tear from the least touoh, and softae- 



* 3d Memoir, p. 70. 

 f John Fitch, Es.q.'- 



