The Zoologist— June, 1868. 1225 



The American Silk-worm. By L. Trouvelot.* 



The insect fauna of North America contains several gigantic 

 species of moths belonging to the Lepidopterous family Bombycidae. 

 This family has long been known to spin, when in the larval or cater- 

 pillar state, a cocoon which produces a large amount of silk, with a 

 fibre of the most delicate texture, of great strength and of the most 

 beautiful lustre. Every one is familiar with the beautiful and delicate 

 fabric made from the fibres spun by that crawling repulsive creature, 

 the silk- worm. Our country alone has eight or ten species of silk- 

 worms : two of these, Callosamia Promethea and C. angulifera, feed 

 on the lilac and wild cherry: they spin a small elongate cocoon of so 

 very dense texture and so strongly gummed, that I have failed in all 

 my attempts to reel the silk from the cocoon. These cocoons resemble 

 very much those ofSamia Cynthia, or, the Ailanthus silk-worm, recently 

 introduced into Europe from China, but the cocoon is of a looser tex- 

 ture. Platysamia Etuyale, P. Columbia and P. Cecropia feed upon 

 many different species of plants : they make a large cocoon, within 

 which is another cocoon, or inner layer, of an oval form ; but as the 

 larva in spinning the cocoon leaves one end open for the exit of the 

 moth, this prevents the reeling of a continuous thread : the silk, though 

 quite strong, has not much brilliancy, and the worm is too delicate to 

 be raised in large numbers. The caterpillar of Tropaea Luna, the mag- 

 nificent green moth with the long tail-like expansion of the hind wings, 

 feeds upon the oak, sycamore and other trees, and spins an oval 

 cocoon, which, however, is so frail and thin, and the fibre so weak, 

 that it is impossible to reel it. 



Practically, however, the larva of Telea Polyphemus is the only 

 species that deserves attention. The cocoons of Platysamia Cecropia 

 may be rendered of some commercial value, as the silk can be carded, 

 but the chief objection, as stated above, is the difficulty of raising the 

 larva. The Polyphemus worm spins a strong, dense, oval cocoon, 

 which is closed at each end, while the silk has a very strong and 

 glossy fibre. For over six years I have been engaged in raising the 

 Polyphemus worm, and here present the following imperfect sketch 

 of the progress made from year to year in propagating and domesti- 

 cating these insects from the wild stock. 



* Reprinted from the ' American Naturalist,' published by the Esse\ Institute, 

 Salem. 



SECOND SERIES — VOL. III. 2 U 



