Habitat quality and management for the northern brown argus butterfly Aricia artaxerxes (Lepidoptera: Lycaenidae) in North East England Original Research Article

An experimental study at four North East England sites, was used to examine ovipositing preferences in the scarce northern brown argus butterfly Aricia artaxerxes. The impact of grazing management on habitat quality and adult population dynamics was examined using transect counts over a 10-year period at Thrislington Plantation NNR. The selection of ovipositing sites was not dependent upon the abundance of the hostplant, common rock-rose Helianthemum nummularium, or on the presence of bare ground. Eggs were frequently laid on the younger, second and third pair of leaves from the tip of the hostplant shoot and selected leaves were larger than leaves of randomly selected plants. In a laboratory experiment, hostplants treated with nitrogen, with larger and thicker leaves were selected for ovipositing most frequently. Fewer eggs were laid in managed (shorter vegetation) than unmanaged (taller vegetation) experimental plots and similarly, adults were much less abundant in grazing compartments subjected to higher grazing pressures, although recoveries were apparent once these were relaxed. A. artaxerxes is able to survive in a range of sward heights, but population densities were lowest in short vegetation (<5 cm) and increased in medium (6–10 cm) to tall (>10 cm) swards. Grazing pressures less than about 0.2 Livestock Units appeared to be most beneficial. The implications of these results for the conservation A. artaxerxes sites are discussed.