It is said that "Aojuku" has been selected by Ohashi Isaburo(or Ohashi Shigezaemon, Isaburo' father), a habitant of Kaketa village of Date district, in the era of Tenpo(1830-1844) or Kaei(1848-1854). He selected a cocoon of middle cocoon filament size from among Aobiki strains, those were the strain of Akajuku (Kawahisa strain). It was written in "Kaiko-No-Shuruigo" that Aobiki was selected from among Kawahisa strains of Akajuku in around the 5th year of Kaei(1852), laying stress on the following points:
(1) Healthiness of silkworm
(2) Size of cocoon filament(Middle size was preferred in those days)
(3) Quality of cocoon filament

Aojuku held an important position in the era of Meiji(1868-1912). And it was a white cocoon and univoltine race which had been lauded and used with "Matamukashi" particularly since around the 30th year of Meiji(1897). Many new races were bred by selection or cross breeding of Aojuku strains in the era of Meiji(1868-1912). Those improved races were used by the name of Aojuku.
The comparison of characteristics between Aojuku and Akajuku is presumed as follows:
(1) Aojuku is small peanut shaped. Akajuku is a little greater peanut shaped than Aojuku.
(2) Aojuku is smaller than Akajuku in cocoon filament weight and cocoon filament size.
(3) Aojuku is larger than Akajuku in healthiness of silkworm.

As the improvement in the characteristics of Aojuku mentioned above was continued, Aojuku was widely used in the era of Meiji(1868-1912) without a period of decline. On the other hand, Akajuku was criticized for difficulty of rearing and large cocoon filament size, and then declined presently. There is a different opinion about the origin of Aojuku. It was said that the selector of Aojuku was Ohashi Sai of Kaketa village. When he served under the Ohashi Isaburo family, he found incidentally a silkworm which span blue filament in the 3rd year of Bunkyu(1863). After the repeated selection for 4 years, Aojuku was established as a race in the 1st year of Genji(1864).
About the matters mentioned above, Neriki Kizo explained as follows in "Sanshu Yoroku": "Both of the Ohashi Isaburo family and the Ohashi Sai family were awarded the First Medal for Merit at the Third National Industrial Exhibition in the 23rd year of Meiji(1890). In view of these facts, it was presumed that Ohashi Isaburo received wide recognition as a head of the breeder and Ohashi Sai as a selector of the race."
Dr. Toyama Kametaro stated as follows: "Akajuku strains were classified into two categories in the 8th year of Meiji(1875). The one is "Aobiki" and the other is "Akajuku". It was presumed that Aojuku peanut shaped was divided from Akajuku large shaped from the 14th year of Tenpo(1843) to the end of Kaei era(Kaei: 1848-1854)." Aojuku of univoltine was held to be important in the era of Meiji(1868-1912) and followed in of Taisho(1912-1926). Aojuku was improved individually by the government of Hokkaido, Tokyo, Kanagawa, Yamanashi and Fukui Prefecture. And those races were distributed to each districts(prefectures), respectively. On the other hand, private breeders improved excellent Aojuku races. Those Aojuku races were excellent in the heathiness of silkworm and the quality of cocoon filament, and then widely used to be valuable.

(Private breeders' silkworm races were following breeders' : Kato Zenbei (Fukushima Prefecture), Matsushiro Silkworm Races Co.Ltd. (Nagano Prefecture), etc.)
Production of Aojuku in Japan(in the 1st year of Taisho(1912)): 353,000 moths
(It is presumed that one moth will hatch 400 eggs.)

1) Eikichi HIRATSUKA(1961) : History of Modern Silkworm Race Breeding, Dainippon Silk Foundation, Silk Science Research Institute, pp236
2) Eikichi HIRATSUKA(1969) : Genealogy of Japanese Silkworm Races for Practical Use, Dainippon Silk Foundation, Silk Science Research Institute, pp335