A new non-cocooning silkworm variety, Hachojam, suitable for autumn rearing season is single cross Fl hybrid between Japanese race Jam 307 and Chinese race Jam 126. Jam 307, Japanese parent of the Hachojam, which is a source for non-cocooning process showed a high GCA (generation combining ability) in naked pupation rate and Jam 126, Chinese parent, showed a high GCA in pupation rate and single pupal weight. In the local adaptability test performed at 8 local areas in autumn of 1999 to 2000, the naked pupation rate and thin cocoon rate of Hachojam were 64.7% and 35.3% , respectively. The pupal weight calculated from 10,000 of the 3rd molted larvae was 24% heavier in Hachcjam than the cocoon-producing, check variety Daesungjam.