The division of _Bombycina_ contains the largest of moths, and at the same time species of a middle and small size. These moths take no nourishment, and live only for a short time--long enough to propagate their species. They rarely fly during the day, only showing themselves in the evening. The group is dispersed over nearly all parts of the world, and may be recognised by the antennæ generally being cut like the teeth of a comb in the males, by their thick, strong bodies, and, in the majority of cases, by their large head, by their wings more or less large, and by their heavy flight. [Illustration: Fig. 200.--Larva of the Poplar Hawk-Moth (_Smerinthus populi_).] In the _Bombycina_ are found the genera _Sericaria_, _Attacus_, _Bombyx_, _Orgyia_, _Liparis_, &c. It is to the genus _Bombyx_ that the silkworm belongs, that celebrated insect called by Linnæus _Bombyx mori_, a name which reminds us at the same time of its most ancient denomination, and of the mulberry tree, on which these caterpillars feed. M. Guérin-Méneville has called the silkworm "the dog of insects," for it has been domesticated from the most ancient times, and has become deprived of great part of its strength in the process. The moth of the silkworm can no longer keep its position in the air, or on the leaves of the mulberry when they are agitated by the wind. It can no longer protect itself, under the leaves, from the burning heat of the sun and from its enemies. The female, always motionless, seems to be ignorant of the fact that she has wings. The male no longer flies; he flutters round his companion, without quitting the ground. It ought, however, to be possessed in the wild state of a sufficiently powerful flight. M. Ch. Martins found that after three generations reared in the open air, the males recovered their lost power. Before speaking of the different phases of the life of the silkworm and the rearing of this precious insect, we will notice the origin and progress of the silk trade, one of the most important branches of commerce in the South of Europe and in the East. The native country of the silkworm is not better known than that of the greater number of plants and animals which form the staple of agricultural industry. Probably, however, it was China. It was certainly in this vast empire that long since the business of fabricating silk began. One reads the following in "L'Histoire générale de la Chine," by M. Mailla:-- "The Emperor Hoang-ti, who lived 2,600 years before our era, wished that Si-ling-chi, his wife, should contribute to the happiness of his people; he charged her to study the silkworm, and to try to utilise its threads. Si-ling-chi caused a great quantity of these insects to be collected, which she fed herself in a place destined exclusively for the purpose; she not only discovered the means of rearing them, but still further the manner of winding off their silk and of employing it in the manufacture of fabrics."