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Updated: June 22, 2025
As I have stated in former years, this is the best North American silkworm, producing a closed cocoon, somewhat smaller than that of Pernyi, but the silk seems as good as that of Pernyi. The cocoons of Polyphemus I had in 1881 were smaller and inferior in quality to those I had before.
I bred them under glass, in a green-house. A certain number of the larvae were unable to cut the shell of the egg. Here are a few notes I find in my book: Ova of Roylei commenced to hatch on the 29th of June; second stage commenced on the 9th of July. The larvae in the first two stages seemed to me similar to those of Pernyi, as far as I could see.
The hybrids hibernated in the pupa state. Roylei, as Pernyi, hibernates in the pupa state. In the November number, 1881, of "The Entomologist," Mr. W.F. Kirby, of the British Museum, wrote an article having for its title, "Hermaphrodite-hybrid Sphingidae," in which, referring to hybrids of Smerinthus ocellatus and populi, he says that hermaphroditism is the usual character of such hybrids.
Of such species as Attacus pyri, of Central Europe, and Attacus pernyi, the North Chinese oak silkworm, which I have mentioned in my previous reports, and bred every season for several years, I shall only say that I never could rear Pyri in the open air in London, up to the formation of the cocoon.
The larvae of Polyphemus can be bred in the open air in England, almost as easily as those of Pernyi, and even Cynthia; they will pass through their five stages and spin their cocoons on the trees, unless the weather should be unexceptionally cold and wet, as was the case during the month of August, 1881, when the larvae had reached their full size; they were reared this year on the nut-tree, and some on the oak.
A., on the prehensile use of the tarsi in male moths; on the rearing of the Ailanthus silkmoth; on breeding Lepidoptera; proportion of sexes of Bombyx cynthia, B. yamamai, and B. Pernyi reared by; on the development of Bombyx cynthia and B. yamamai; on the pairing of Bombyx cynthia.
I do not think that such will be the case with the moths of the hybrid Roylei-pernyi, on account of the close relationship of Roylei with Pernyi, but nothing certain can be known till the moths have emerged. Here are the few notes taken on the hybrid Roylei-pernyi: Ova commenced to hatch on the 12th of June; these were from the pairing which had taken place on the 21st of May.
I have said that it is extremely difficult to obtain the pairing of Roylei moths in captivity. But the male Pernyi paired readily with the female Roylei. I obtained six such pairings, and a large quantity of fertile ova.
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