In another letter, dated November 25, 1881, my correspondent says: "I am
sorry that you have not had better success in the rearing of your
larvae, but you should not despair. It is possible that the choice of an
improper food-plant may have as much to do with failures as the coldness
and dampness of the English climate. I lost many thousands of Atlas
caterpillars before I found out the proper tree to keep them on in a
domesticated state; and when I did attain partial success, I could
not keep them for more than one generation, till I found the _Milnea
roxburghiana_ to be their proper food plant. I do not know the proper
food-plant of the Mylitta (Tusser), but I have succeeded very well with
it, as it is a more hardy species than the Atlas. Though a Bombyx be
polyphagous in a state of nature, yet I think most species have a tree
proper to themselves, on which they are more at home than on any
other plant. I should like, if you could find out from some your
correspondents in India, on what species of tree Mylitta cocoons are
found in the largest numbers, and what is about the greatest number
found on a single tree. The Mylitta is common enough here, but there
does not seem to be any kind of tree here on which the cocoons are to be
found in greater numbers than twos and threes; and there must be some
tree in India on which the cocoons are to be found in much greater
plenty, because they could not otherwise be collected in sufficient
quantity for manufacturing purposes. The Atlas is here found on twenty
or more different kinds of trees, but a hundred or a hundred and fifty
cocoons or larvae may be found on a single tree of _Milnea roxburghiana_,
while they are to be found only singly, or in twos and threes, on any
other tree that I know of. The Atlas and Mylitta seem to be respectively
the Indian relations of the Cynthia and Pernyi. It is, therefore,
probable that the Ailantus would be the most suitable European tree for
the Atlas, and the oak for the Mylitta."