Sustainable livestock grazing is challenging in Mediterranean mountainous grasslands, under the increasing aridity stress, stemming from global warming. We aimed to define the optimal range of stocking rate for insect diversity conservation in mountainous grasslands (1,470-1,850 m) in Pindos Mountain Range in Greece (nine mountains, including protected areas of the Natura 2000 network). We sampled 32 sites along a gradient of pasture quality (LAI-Leaf Area Index) and humidity (NDII-mean Normalized Difference Infrared Moisture Index). For three butterfly seasons (June-July-August 2024), we recorded 104 butterfly species across one transect (300 x 5 m) per site, and 14 microhabitat parameters across four plots (5 x 5 m) per site. During August, we recorded 47 Orthoptera species in the same plots. We produced the Time-Weighted Grazing Index (TWGI) (96 values: 32 sites X 3 seasons), by multiplying the Livestock Units/ha (data collected from interviews with 55 livestock farmers) with the number of grazing days/ overall days of the vegetation growth season, implying the butterfly flight period window. Pasture quality (LAI), humidity (NDII), vegetation height and cover, and flowerheads significantly decreased from June to August, and TWGI and litter cover increased. Models showed that TWGI negatively affected vegetation height, vegetation cover and flowerhead abundance, and positively litter cover. Models also showed that vegetation heights of 15–20 cm ensured the highest butterfly species richness and abundance (and a litter cover of 25-30% only for butterfly species richness). Orthoptera species richness peaked at 1,650–1,750 m elevation and 20–50% vegetation cover, with their abundance positively related to vegetation height and negatively to stone cover. Preliminary findings suggest a stocking rate of up to 0.041 LVU/ha in arid pastures (NDII0.2) to maintain adequate vegetation height and cover for butterfly and Orthoptera conservation in the high mountains. These results underline the need to define sustainable grazing management plans in the mountainous pastures accounting for both livestock farming sector sustainability and biodiversity conservation, under climate change. This study was funded by H.F.R.I. (LIVEMOUNT project).