relict — boreal owl, white-backed woodpecker and Eurasian three-toed woodpecker. The park's rarest residents are lesser spotted eagle with a single nesting pair, booted eagle, golden eagle with 2 to 5 pairs, short-toed snake eagle with two pairs, saker falcon, peregrine falcon with three pairs, western capercaillie, hazel grouse, rock partridge, corn crake, Eurasian woodcock and stock dove. There are 11 reptile and 8 amphibian species. There are Central European species (fire salamander, yellow-bellied toad, smooth snake), Palearctic (common toad, European green toad, common frog), Euro-Siberian (European tree frog, common European viper, grass snake, viviparous lizard), Irano-Turanian (marsh frog), Southern European (agile frog), Euro-Mediterranean (European green lizard), Mediterranean (common wall lizard) and Balkan (Erhard's wall lizard). The ichthyofauna includes 6 fish species: common minnow, European eel (considered extinct), western vairone, brown trout, rainbow trout and brook trout. The limited number of species is determined by the high elevation of the park. The glacial lakes, streams and upper river courses are inhabited by few fish species. The western vairone is known only from the Kremenski lakes and might in fact represent a new undescribed species. The number of identified invertebrate species in Pirin National Park is 2091, which is 40% of the estimated 4500 species to inhabit the park. They are poorly researched and there is not enough data to assess the qualitative and quantitative parameters even of the main populations of endemic and relict species. There are 218 endemic, 176 relict and rare 294 species. The Araneae are represented by 321 species, or 35% of Bulgaria's total. The spiders prefer the north-eastern slopes and are most diverse in the coniferous forests. There are 36 species of Myriapoda, or 20% of Bulgaria's total. They are distributed mainly in the forests and are less frequent in the sub-Alpine and the Alpine zones. The Mollusca are 89 species and represent 27% of the nation's total (excluding the marine molluscs). Only 2% of Bulgaria's Ephemeroptera are found in the park — two species. The number of Orthopterida species is 63, or around 30% of the nation's total. The highest diversity is found in the valleys of the rivers Banderitsa and Damyanitsa. The Plecoptera are represented by 40 species, forming 40% of Bulgaria's diversity. There are 323 Heteroptera species, or 32% of the ones known in Bulgaria. They are most diverse in the northern parts of the park, in the Bayuvi Dupki–Dzhindzhiritsa Reserve. The Coleoptera