# Habitat Loss and Other Threats to the Survival of _Parnasius apollo_ ([PERSON], 1758) in Serbia
## 1 Introduction  
### Taxonomic Background and Regional Status  
_Parnasius apollo_ ([PERSON], 1758), stands as one of the most iconic butterflies of Eurasian montane ecosystems, first described from southern Sweden. Over the decades, more than 200 subspecies have been proposed across its expansive range, especially in the Alps. However, recent taxonomic revisions have cast doubt on the validity of many of these forms, suggesting that a substantial number were established largely for commercial purposes--to artificially enhance specimen value and stimulate commercial collection and trade [1]. It is a charismatic butterfly species often associated with alpine and subalpine habitats [2], particularly in Western Europe. However, across much of its range in Central and Eastern Europe, as well as parts of Asia, the species occurs at lower elevations, inhabiting open, rocky calcareous slopes and limestone outcrops, often in warm, xeric conditions [3; 4]. In these areas, it is not restricted to high-altitude environments but thrives in habitats shaped by traditional land use, such as moderate grazing and haymaking, which prevent forest encroachment and maintain open conditions suitable for its larval food plants (e.g., _Sedum_ spp.) As a stenophagous species restricted to ecologically narrow alpine and subalpine habitats, _P. apollo_ is acutely vulnerable to climatic shifts and habitat degradation [1]. Throughout Europe, its populations have experienced precipitous declines, with confirmed local extinctions in several Central European mountain systems [1]. In Finland, population collapses began as early as the 1930s, leading to disappearance from numerous formerly occupied sites within three decades--a pattern attributed primarily to increased atmospheric deposition of heavy metals linked to industrial emissions [5; 6]. In Serbia, _P. apollo_ has been documented for over a century [7; 8], with two recognized subspecies: _jelicus Frubstorfer_ and _timacus Varga & Lelo_[9]. In the eastern region of Timocka Krajina, three historical strongholds have been identified--Stol, Janosica, and Vetren. While only sporadic individuals have been reported at Janosica and Vetren, the population at Mount Stol--proposed as a geographically distinct and taxonomically valid subspecies (_timacus_ ssp. nov.)--was once estimated at several hundred individuals [8]. The Stol habitat is defined by its limestone substrate and the presence of _Sedum album_, the larval host plant, with notable year-to-year fluctuations in population size recorded during the late 1960s and early 1970s. Approximately 70 km southeast of Mount Stol, near the Bulgarian border, four additional historical sites have been noted: Janosica and Vetren (as above), and Topli Do (800 m) and Toplodolska Reka (900 m) [10]. These localities represent the nearest historical populations to Stol. Recent findings from Stara Planina [11] confirm the continued presence of the species and its protection under several international conservation frameworks, including the EU Habitats Directive (Annex IV), CITES, and the European Red List of Butterflies, where it is classified as Near Threatened (NT) [12]. In Serbia, it is listed as Vulnerable (V) according to national IUCN criteria [10]. Additional records exist from Mount Kopaonik, at two sites: Bele Stene and Dorov Most [13; 14]. However, no viable population has been observed at Mount Stol since 2017, and Bele Stene has yielded no sightings for over seven years. These alarming regional declines prompted the present study, which includes specimens from the surviving Dorov Most population. Recently published data also confirm the occurrence of _P. apollo_ at the Rastiste locality on Mount Tara, near the border with Bosnia and Herzegovina [15]. In stark contrast, the species is now classified as extinct (EX) in Romania, with no confirmed observations at any of its six historical regional sites since the mid-20 th [16]. The conservation crisis of _P. apollo_ mirrors the broader vulnerability of emblematic insect species.