Abstract. Pig breeding is inevitably accompanied by an attack on animals by a large number of flies. Effective fly control requires biological information about the dynamics of the fly population over the seasons. The aim of the study was to determine the number and species composition of flies in the conditions of the Khatas pig farm in the winter. Methods. In the Khatas pig farm, during the technological cycle of production in December 2021, studies were carried out to determine the number of flies. To count the number of flies in the pigsties of the breeding, reproduction and fattening shops, traps were installed in the form of sticky tapes 84 cm long. There were 15 pigsties in three workshops of the pig farm. In each pigsty, one trap was placed at a height of 1.5 m from the floor. The number of insects caught on the glue trap was counted after 24 hours under laboratory conditions. Data analysis was carried out according to the method of V. N. Beklemishev. A trap with an exposure of 24 hours was taken as the unit for counting the number of flies. Results. For the first time, research has established the spread of flies in winter during the technological cycle of production at Khatas pig farm LLC. During the day, 1102 flies were caught by traps in three workshops. The species composition of flies in winter was represented by one species of Musca domestica L .The abundance index of adult flies in the rearing shop was 30.25 ± 7.56 flies per trap-day, and in the reproduction and fattening shops – 34 ± 5.78, and 57.2 ± 8.55 flies per trap-day, respectively. The scientific novelty lies in the fact that the number of adults of flies and their species composition in the Khatas pig farm of Yakutia in the winter period were determined for the first time in the obtained materials.