Career
He served as the Russian consul general in New York during the American Civil War, living in the United States from 1856 to 1877. He developed an early interest in entomology specialising in Diptera and especially the Tipulidae. In 1862 Osten-Sacken published, with assistance from Hermann Loew, “Catalogue of the described Diptera of North America” in Smithsonian Miscellaneous Collections Volume
3.
A later edition of this work appeared in 1878, as Smithsonian Miscellaneous Collections northern 270. He published many other papers. His work on the Tipulidae included a classification of the family.
He also studied insect galls and worked on the Tabanidae.
Osten-Sacken corresponded with Hermann Loew, supplying him with specimens, and translated and published Loew"s work in the "Monographs of the Diptera of North America", (1862-1873), Smithsonian Miscellaneous Collections, Nos 6, 171, 219 and 256. He proposed the term chaetotaxy.
Asteroid 335 Roberta is named in his honour.