, as we
have seen, queens and drones cannot be selected and paired.

{300}

SILK-MOTHS.

These insects are in several respects interesting to us, more especially
because they have varied largely at early periods of life, and the
variations have been inherited at corresponding periods. As the value of
the silk-moth depends entirely on the cocoon, every change in its structure
and qualities has been carefully attended to, and races differing much in
the cocoon, but hardly at all in the adult state, have been produced. With
the races of most other domestic animals, the young resemble each other
closely, whilst the adults differ much.

It would be useless, even if it were possible, to describe all the many
kinds of silk-worms. Several distinct species exist in India and China
which produce useful silk, and some of these are capable of freely crossing
with the common silk-moth, as has been recently ascertained in France.
Captain Hutton[498] states that throughout the world at least six species
have been domesticated; and he believes that the silk-moths reared in
Europe belong to two or three species. This, however, is not the opinion of
several capable judges who have particularly attended to the cultivation of
this insect in France; and hardly accords with some facts presently to be
given.

The common silk-moth (_Bombyx mori_) was brought to Constantinople in the
sixth century, whence it was carried into Italy, and in 1494 into
France.[499] Everything has been favourable for the variation of this
insect. It is believed to have been domesticated in China as long ago as
2700 B.C. It has been kept under unnatural and diversified conditions of
life, and has been transported into many countries. There is reason to
believe that the nature of the food given to the caterpillar influences to
a certain extent the character of the breed.[500] Disuse has apparently
aided in checking the development of the wings. But the most important
element in the production of the many now existing, much modified races, no
doubt has {301} been the close attention which has long been applied in
many countries to every promising variation. The care taken in Europe in
the selection of the best cocoons and moths for breeding is notorious,[501]
and the production of eggs is followed as a distinct trade in parts of
France. I have made inquiries through Dr. Falconer, and am assured that in
India the natives are equally careful in the process of select