.The body size of xylophagous beetles is determined by the host plant species, as well as by the amount and quality of breeding material. Consequently, the biometric traits of adults can be used as an indicator of the attractiveness of the breeding material and the quality of a habitat. The paper presents selected biometric traits of rosalia longicorn Rosalia alpina (L.) imagines in three populations from the Beskid Niski Mts (Carpathian Mts, south-eastern Poland). Two populations of this

more »

... from managed forests and one from a protected area in the Magura National Park were compared. The former developed on two different host plants (European beech Fagus sylvatica and wych elm Ulmus glabra), the latter on European beech. No significant differences were found between the biometric traits of imagines from the three populations. No intersexual differences were found for the width of the pronotum in any of the populations, but females had longer elytra than males in all the populations. The lack of body size differences in these populations potentially indicates that this species occurs only in favourable habitat conditions. The limited species range and the patchy distribution of the rosalia longicorn are indications of its stringent habitat requirements and its dependence on forest management. Habitats supplying a sufficient amount and quality of suitable breeding material for the development of the rosalia longicorn should be protected.