100 NATURAL HISTORY. [cH. V. 



day; while at 71<> it requires six or seven days. 

 The second moulting, which at 75° is wrought in 

 foui days, at 69"^ and 71° takes six days for its ac- 

 complishment. Thus, by foresight and prudence, 

 the proprietor will be enabled to gain seven or eight 

 days, which prevents any ill effect from the unfa- 

 vourableness of the season ; and this time gained, 

 it is evident, may be of the utmost consequence, for 

 in the year 1813 the silkworms were reared in thirty- 

 one days, and it required thirty-eight days to raise 

 them in 1814, to allow time for the growth of the 

 mulberry leaf; and I do not comprise in these seven 

 days which I gained, three days which I delayed in 

 the hatching of the silkworms, having perceived 

 that the whole season was bad. Those who are 

 not careful thus to meet the accidental untoward- 

 ness of seasons, and by art to prevent their injuries, 

 would be obliged eitlier to throw away the early 

 hatched eggs, or to strip the mulberry-tree too 

 soon, and injure the leaves which are to feed the 

 silkworm in its adult stages hereafter. These con- 

 siderations must strongly impress the necessity of 

 delaying the hatching of the eggs by some days, 

 rather than hurry their coming forth ; particularly 

 as there is no fear, when worms are reared in this 

 secure manner, of their being injured ; should there 

 occur two or three hot days, these would only ac- 

 celerate the moulting a few days sooner. It is also 

 certain that the later silkworms, in their last stage 

 of progress, make choice of the leaves suitable 

 to their age, and particularly those leaves which 

 are quite ripened, which, for the proprietor's in- 

 terest, is the most important period, as it is at that 

 last period the greatest consumption of the leaves 

 occurs." 



That a great degree of heat will be borne is 

 proved by the following facts : — 



" It cannot be said that silkworms are injured by 

 any degree of heat in these climates, however con 



