To study the diversity of agromizids (leaf miners) in the South Caucasus, the species external morphological features, their host plants, the development of larvae and pupae and to assess the degree of crop infestation by leaf‐miners.The study was carried out within the framework of the scs 21‐002 scientific program “Leaf miners as pests of agricultural plants (Diptera: Agromyzidae): the latest control measures”. Type samples were fixed in 75 % ethyl alcohol and deposited in the Agrarian Scientific Research Laboratory of the Scientific Centre of Zoology and Hydroecology. Species were identified by examining the male genitalia. The degree of damage of the host–plant was determined based on intensity indicators.As a result of this research, a new species of the Calycomyza genus was discovered in the South Caucasus fauna. Larvae of C. jucunda (Wulp, 1867) were found on the leaves of Beta vulgaris, a host plant mentioned for the first time here. As a Nearctic species, it was also first discovered in the southern Caucasus.The study of the male genitalia indicates expansion of the biogeographical distribution of Calycomyza species, as most of them are found in the Nearctic and Neotropical regions. In terms of intensity, C. jucunda is classified as a less dangerous species for agricultural crops.