Abstract: The first studies of the host-ant relationships of Maculinea rebeli in Lithuania were carried out. The sites are the northernmost localities of the whole known species range in Europe. Larvae, pupae and an exuvium of the butterfly were found exclusively inside Myrmica schencki nests. Myrmica sabuleti, M. lonae, and M. rugulosa were not exploited. Our results are similar to data from France and Spain but differ clearly from observations of the nearest Polish population, which strongly suggests geographical variation in host-ant specificity of M. rebeli in the eastern range of species distribution. The knowledge obtained is also vital for M. rebeli conservation in Lithuania.