The Japanese silk moth or Japanese oak silkmoth (Antheraea yamamai, Japanese: Yamamayu(ga)(山繭(蛾)・ヤママユ(ガ)?) or tensan(天蚕?)) is a moth of the Saturniidae family. It is endemic to east Asia, but has been imported to Europe for Tussar silk production and is now found in South-Eastern Europe, mainly in Austria, North-Eastern Italy and the Balkan. It seems to be spreading north and a population near Deggendorf and Passau (Bayern) has been reported. It has been hybridized artificially with Antheraea polyphemus of North America.
Front view of a male specimen
2nd instar larva
This moth has been cultivated in Japan for more than 1000 years. It produces a naturally white silk but does not dye well, though it is very strong and elastic. It is now very rare and expensive.
The wingspan is 110–150 millimetres (4.3–5.9 in). Adults are on wing from August to September in one generation depending on the location.