The study of entomopathogenic microbes represents some important aspects in the microbial ecology and biotechnology. For the first time the microbial nature of muscardine, the infectious disease of silkworms (Bombyx mori L.), was described by the Italian mycologist A.Bassi in 1835. Among the most brilliant investigations of entomopathogenic microorganisms we must certainly mention classical works of Louis Pasteur on the diseases of silkworms (1865). These investigations were really of great fundamental and practical, economic importance. Pasteur described the agents of infection and found the way to eliminate the epidemic of silkworms. Moreover he formulated the basic principles of infectious pathology and epidemiology that signified a new step in the development of medicine. Pasteur proposed to utilize entomopathogenic microbes against harmful insects. This idea turned out to be very fruitful. It was largely developed by many microbiologists, for example, by some scientists of the Pasteur Institute (Paris), especially in the laboratory of E.Metchnikoff. Among them we can mention I.M.Krassiltschik (1857–1920), a microbiologist from Chisinau, who worked in the laboratory of Metchnikoff in 1904–1905. The investigations of entomopathogenic bacteria in the Pasteur Institute are also linked with the names of Russian emigrants S.I.Metalnikoff, K.Toumanoff and some others. Many species of entomopathogenic bacteria were described, and among them the famous Bacillus thuringiensis with its numerous strains and serovars with high specificity to different insects. On the base ot B.thuringiriensis Metalnikoff organized in 1940s the production of bacterial preparation with insecticidal activity which was successfully used in Egypt against the pest of cotton. One of the strains of B.thuringiensis was isolated by Toumanoff in Ales, the place, where Pasteur performed his investigations on silkworms; it was named B.thuringiensis var. alesti. On the base of B.thuringiensis a large-scale production of insecticides against harmful insects was organized in USSR, in 1960s it reached 6–8 t per year. Among soviet scientists who largely contributed to the development of this field of biotechnology it is important to remind today the name of the outstanding soviet and Armenian scientist, microbiologist and biotechnologist, academician E.G.Afrikian (1925–2016). During many years E.G.Afrikian headed the Institute of Microbiology in Yerevan, he also organized the production of insecticides at the factory of biochemical preparations in Abovian), founded the Collection of Cultures of entomopathogenic bacteria, participated in the creation of the database on entomopathogenic bacilli, conducted the scientific work in the Centre Armbiotechnology (Yerevan). Evrik Gegamovitch Afrikian was inspired by the works and ideas of Pasteur. During his work in Pasteur Institute (1964–1965) he could analyse numerous materials of the Pasteur museum and Archives. He found the similarity between some modern entomopathogenic bacteria from Ales and bacteria described by Pasteur. In one of his last articles [1] he discussed the idea about the possible correlation between auxotrophic and pathogenic properties of entomopathogenic microbiota. Some of his works deal with the cosmic microbiology, for example, the study of properties of B.thuringiensis after incubation in outer space. The scientific heritage of academician E.G.Afrikian is a brilliant page in the history of microbiology and biotechnology.