This dissertation examines how a biological research organism played an important role scientifically, economically, and culturally in East Asia. Historical analysis of silkworm breeding in Japan allows the study of a critical yet understudied aspect of Japanese experimental biology: the relationship between silk manufacture and the emergence of modern Japanese genetics. I intend to research the development of Japanese genetic expertise concerning the rationalization of silkworm reproduction from the 1880s through the 1920s as silk became one of Japan’s most valuable export products. The silkworm, normally associated with family farms, emerged as an exemplary research organism and site of contestation as craftspeople, industrialists, and scientists sought to improve qualities of silk. As Japanese biologists investigated silkworm heredity, the tendency to explain society with genetics gained currency within their scientific community, adding uniquely to policy discussions, such as critiques of education spent on people with “inferior” heredities, to claims of equal genetic diversity shared by Japanese and American people in order to protest the exclusionary 1924 U.S. immigration act. I will explore how the genetic standardization of silkworm varieties interacted with the household craft of silkworm breeding in Japan and how expertise about heredity was tested and applied not only to silkworms but also to humans. In particular, I aim to reconstruct the history of the scientific manufacture of F1 (first generation) hybrid silkworms, and the social changes surrounding the adoption of hybrid silkworm eggs by silk farmers. The F1 hybrid silkworm is a result of selective breeding experimentation, a technique initially developed by scientist Toyama Kametaro (1867-1918). I will specifically compare the Japanese language technical and non-technical writings of silkworm scientists such as Toyama, along with their English publications.