Agricultural intensification in Europe led to a massive loss of biodiversity since the second half of the 20th century. One group of species which is affected are butterflies which are often used as indicators for the ecological condition of cul-tivated land. The Large Copper (Lycaena dispar) is a butterfly of the family of blues (Lepidoptera: Lycaenidae) which is vulnerable in its western European distribution but stable in Eastern Europe. It is an oligophagous species with a strong link toRumex species for oviposition. We analyzed the oviposi-tion behavior of Lycaena dispar rutilus in 12 agricultural sites in Transylvania/Romania in relation to different land use types and attributes of the host-plants. Guided by three hypotheses, leaves of Rumex plants were examined for eggs and specific attributes of host-plants and the surrounding land use were recorded. Through variance and regression analyses, the pre-sence of eggs was tested for a relation to structural environ-mental parameters. 132 eggs were found on 71 plants in 8 of the 12 sites. 42 eggs on 38 plants belonged to the first gene-ration. With a total of 26 eggs, Rumex obtusifolius turned out to be the preferred plant for oviposition. Rumex confertus was identified as a new host-plant. The height of host-plants and land use type were identified as positive significant explanato-ry variables for oviposition. To promote the expansion of the butterfly in Transylvania extensive land use with a variety of habitat structures as well as continued maintenance of gras-slands by mowing is recommended