Silk Manujaclure. 251 



silkworms could not safely be fed on lettuce leaves for a longer pe- 

 riod than three weeks; as on persisting further in their use, the 

 greater part of the worms died without forming their cocoons. 

 Some, indeed, possessed sufficient vigor to spin and to produce 

 perfect and well-formed balls, even when lettuce leaves had con- 

 stituted their only food. Reasoning from this fact, Miss Rhodes 

 was brought to suspect that the premature mortality of her brood 

 was not altogether occasioned by the unwholesome nature of the 

 aliment on which they had fed, but might be owing to some extra- 

 neous circumstance; and further observation led her to the conclu- 

 sion that it was the coldness of the lettuce leaves rather than any 

 inherent property which made them detrimental. This lady hav- 

 ing thence suggested that if the worms were kept in a higher tem- 

 perature, they might be successfully supported through their lives 

 on lettuce leaves; general Mordainit caused a considerable num- 

 ber to be hatched and reared in his hot house. These were fed 

 entirely on lettuce leaves; they throve and went through all their 

 mutations as satisfactorily as if fed with their natural nourishment; 

 scarcely any among them died, and the number and quality of the 

 cocoons that were gathered proved the entire success of the ex- 

 periment. If a sohtary trial be sufficient to establish a fact, this 

 must certainly be satisfactory to those who consider it desirable to 

 naturalize silkworms in England, where, owing to the inequahty 

 of seasons, the appearance of mulberry leaves must always be un- 

 certain in regard to time. Lettuce leaves have an advantage over 

 other vegetables which have been offered as substitutes for the 

 mulberry, that they may be gathered in wet weather without them- 

 selves being wetted, as a lettuce, once cabbaged, resists the en- 

 trance of all moisture within; and the heart being always perfectly 

 dry, ensures nourishment to the worm, free from that moisture 

 which is always found to affect it injuriously. 



' Mrs. Williams, an earher correspondent of the society whose 

 "Transactions " have been quoted, gives a very minute and copi- 

 ous account of the various trials which she made of vegetable sub- 

 stances as substitutes for mulberry leaves. Having hatched her 

 brood in severely cold weather, when even lettuces were not easi- 

 ly procurable, she offered to her worms the tender parts of black- 

 berry leaves, and relates that the worms ate them greedily. She 

 next presented to them young leaves of the elm, and reports that 

 equal success attended this trial: encouraged by these facts, she 

 then succeeded in causing the insects to feed on the leaves and 

 flowers of the sweet cowshp and primrose. But meanwhile the 

 mulberry had put forth its leaves, and having procured some of 

 these for her brood, it was thenceforth vain to offer them any oth- 



