342 on the siH^-'Monn. May 1. 



gold coloured, others orange •, but it is not certain but 

 a change of food may produce some eflFect in this respect. 

 It is, however, very certain, that if different breeds be 

 fed upon the same food, and kept in the same tempera- 

 ture, there will nevcrthelefs be a great diversity in the 

 colour of the silk. This colour does not arise from the 

 silk itself, but merely from the gum with which it is co- 

 vered, for all silk is white when the gum is wafhed from 

 it. 



From the above mentioned particulars it will appear, 

 that the management of silk-worms must be very dif- 

 ferent in hot climates from what is required in those that 

 are colder. At Madras, I learn from Dr Anderson's expe- 

 riments that it is very difficult to prevent the eggs from 

 hatching for a very few days, so that many generations of 

 them must be propagated in one year. " In this hottest 

 season," says he, in a letter to Sir Joseph Banks, dated 

 July 6- 1791, " the fliortest time I have been able to re- 

 mark for the whole evolutions of the silk-worm h forty 

 days •, that is to say, six days an egg tiL'e't.y-two a worm, 

 eleven a grub in the cocoon, and one a moth or butterfly." 

 Fortunately, where the climate forces forward their pro- 

 duction so rapidly, nature hath been equally provident of 

 food for their subsistence •, for in these regions the mul- 

 berry continues to grow and pulli out leaves throughout 

 the whole year. 



In cooler regions, where vegetation is stopped for a 

 season, it is also an easy matter to retard the progrefs of 

 animal life. In some parts of Italy, when the season is 

 favourable, and the mulberry trees recover thi-ir leaves, 

 after being once bared, they rear a second breed towards 

 the end of summer •, but in general they are contented 

 with gathering one full crop in a season. When they 

 wiili for no more, they lay up the eggs in a cool dry 

 place, close wrapped up, where they aay be preserved us 



