EN
The ants Formica polyctena Foerst., F. rufa L., hybrids F. rufa × F. polyctena, and F. pratensis Retz, from the Gorce Mts (the Western Carpathians; southern Poland) were characterized biometrically. Six morphological characters (pigmentation, size, pilosity) of workers were studied. Principal component analysis and cluster analysis were made for the data of 50 samples from wood ant colonies with different social organization and from various habitats (mainly F. polyctena and F. rufa spatially intermingling populations). The results are discussed in the context of taxonomic difficulties within the F. rufa group.