was a Japanese entomologist. He authored numerous texts and was one of the founders of entomology in Japan, responsible for training a generation of Japanese entomologists, and founding the journal ''Zephyrus''. He published numerous papers on the insects of

Micronesia Micronesia (, ) is a subregion of Oceania, consisting of approximately 2,000 small islands in the Northwestern Pacific Ocean. It has a close shared cultural history with three other island regions: Maritime Southeast Asia to the west, Poly ...

and was especially interested in aquatic insects and erected the family

Helotrephidae Helotrephidae is a family of aquatic bugs found mainly in the tropical regions with many species in the Oriental Realm and a few from Africa, Madagascar and South America. These bugs are found swimming or walking amid submerged vegetation in stag ...

along with W.E. China. Esaki was born in

Tokyo Tokyo, officially the Tokyo Metropolis, is the capital of Japan, capital and List of cities in Japan, most populous city in Japan. With a population of over 14 million in the city proper in 2023, it is List of largest cities, one of the most ...

and grew up in

Osaka is a Cities designated by government ordinance of Japan, designated city in the Kansai region of Honshu in Japan. It is the capital of and most populous city in Osaka Prefecture, and the List of cities in Japan, third-most populous city in J ...

. He went to Seventh Higher School Zoshikan (now

Kagoshima University , abbreviated to , is a Japanese national university located in Kagoshima, Kagoshima, Kagoshima, Kagoshima Prefecture, Japan. History The university was established in 1949 consolidating the following schools because of educational reform in ...

) and went to Tokyo Imperial University (now

University of Tokyo The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...

) in 1920 and received a Ph.D. in 1930. He worked extensively on the heteroptera and focused on the Micronesian region. From 1923 he taught at the College of Agriculture, Kyushu Imperial University, Fukuoka. He left the next year and lived in Europe for about four and half years during which time he learned to speak German, Hungarian, Italian, French and Esperanto. He worked with Geza Horvath on hemiptera at Budapest; in 1926, he worked at the Zoological Museum of Academy of Sciences of USSR in Leningrad. He married Charlotte Johanna Hermine Witte in Germany in 1928. They moved back to Japan in 1929 and he became a professor of entomology in 1930 at

Kyushu University , abbreviated to , is a public research university located in Fukuoka, Japan, on the island of Kyushu. Founded in 1911 as the fourth Imperial University in Japan, it has been recognised as a leading institution of higher education and resear ...

. In 1936 he became director of the Hikosan Biological Laboratory, established by baron Takachiho Nobumaro. His major contribution to entomology was the series ''Insects of Micronesia''. He also founded the Japanese journal ''Zephyrus''. A journal named ''Esakia'' was established in his name.

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