Stag beetles (Coleoptera, Lucanidae) are widely distributed throughout the world, with almost 1,600 known species in four subfamilies, namely Aesalinae MacLeay, 1819, Syndesinae MacLeay, 1819, Lampriminae MacLeay, 1819 and Lucaninae Latreille, 1804 (Maes 1992, Smith 2006, Fujita 2010, Bouchard et al. 2011). In the subfamily Lucaninae, the genus Platycerus Geoffroy, 1762, belonging to the monophyletic tribe Platycerini Mulsant, 1842 (Kim and Farrell 2015), includes more than 50 species associated with deciduous forests of the Northern Hemisphere (e.g. Franciscolo 1997, Klausnitzer and Sprecher-Uebersax 2008, Paulsen and Caterino 2009, Fujita 2010, Imura 2010).

Of the seven Platycerus species occurring in the Mediterranean Basin (Bartolozzi et al. 2016), four are recorded in Europe: Platycerus caprea (De Geer, 1774), Platycerus caraboides caraboides (Linnaeus, 1758), Platycerus pseudocaprea Paulus, 1970 and Platycerus spinifer Schaufuss, 1862 (Vit and Bartolozzi 2013, Bartolozzi et al. 2016b). Despite P. caprea and P. caraboides being widely distributed in Europe, they are generally uncommon and even locally rare (e.g. Vit and Bartolozzi 2013, Bartolozzi et al. 2016a, Bartolozzi et al. 2016b, Alekseev 2018, Bartolozzi and Cianfanelli 2018, Bekchiev et al. 2018), possibly due to the short flight period of the adults and their cryptic habits (Franciscolo 1997, Holuša et al. 2006). In Italy, larvae of these two species live in deadwood, especially in hill and mountain forests across the Peninsula (e.g. Franciscolo 1997, Bartolozzi and Maggini 2007). In the European and Italian IUCN European Red List of species, P. caprea and P. caraboides are of “Least Concern” (Audisio et al. 2014, Carpaneto et al. 2015). Italian laws, such as the Regional Law 56/2000 of Tuscany, report these species amongst the taxa that require special attention for habitat conservation (Bartolozzi and Sforzi 2001, Ballerio 2003) and they are included in the saproxylic fauna of relevant interest in forests of protected areas (e.g. PSR 2012, PAER 2013, Regione Emilia Romagna 2018, PIP 2022).

Stag beetles play a vital role in forest ecosystem dynamics, especially where deadwood is abundant. Indeed, most species are saproxylic and, thus, depend on dead or decaying wood for their survival: their larvae feed on the woody material colonised by fungi and other microorganisms (e.g. Tanahashi et al. 2009, Tanahashi et al. 2017). Platycerus caprea and P. caraboides develop in cool, temperate, broadleaf forests and specifically in humid deadwood (Klausnitzer and Sprecher-Uebersax 2008, Lachat et al. 2012, Scaccini 2016, Leidinger et al. 2021, Scaccini 2022). In these habitats, Platycerus species may be exploited by predators, parasites and parasitoids that represent another important element of the saproxylic community (Franciscolo 1997, Klausnitzer and Sprecher-Uebersax 2008, Scaccini 2018b, Scaccini 2020). Both P. caprea and P. caraboides develop on deadwood in a slightly advanced stage of decay, especially in logs small in diameter (< 50 cm) as occurs for P. caraboides, in particular (Scaccini 2016, Scaccini 2022). While P. caraboides seems less dependent on the available deadwood amount in the forest, P. caprea prefers places with a greater amount of deadwood, especially in cooler sites (Lachat et al. 2012). As reported at least for Asian species, Platycerus symbionts prefer cool areas for their development (Tanahashi et al. 2017, Zhu et al. 2022), possibly restricting the habitat range of their hosts that may cover cool environments like mountains in the Italian territory.

Italian occurrences of P. caprea and P. caraboides are often scattered and dated despite these species having been investigated since the 19^th century (e.g. Contarini 1843, Gedler 1863, Ghiliani 1887, Baudi 1889, Stolz 1915, Luigioni 1929, Porta 1932, Müller 1938, von Peez and Kahlen 1977). In these faunistic inventories, distribution data were seldom reported with the indication of precise localities, often requiring further confirmation; this might be the case of P. caraboides in Sardinia, reported by Luigioni (1929) and then quoted by Porta (1932) without a critical review. A detailed faunistic analysis of both species at a national scale was first provided by Dellacasa (1966) and, later, by Franciscolo (1997) and Bartolozzi and Maggini (2007), which included data collected up to 2001; a review of the distributions of the two Italian Platycerus for the last two decades is currently lacking.

This contribution aims to update Platycerus spp. distribution for Italy by revising the existing literature, summarising the present knowledge and adding new records. This overview greatly improves our understanding of P. caprea and P. caraboides occurrence in Italy and will be an important starting point for future analyses and actions aimed at the conservation of these two species.

Geographic coverage

Species identification

Stag beetles collected during field surveys were identified both at larval and adult stages with the help of a magnification lens. Adults collected in the field and those from entomological collections were identified to the specific level by inspecting their genitalia whenever it was possible, for both males and females. For males, we considered, in particular, the margins of the paramera, while for females, we inspected the morphological characters on their gonostyli (e.g. Dellacasa 1966, Franciscolo 1997, Ballerio 2003, Brustel and Van Meer 2020, Figs 2, 3). For the material retrieved online, the identification was performed on external diagnostic features of the adults as reported in the abovementioned identification keys and on their genitalia features when available. Data of insects with doubtful location and/or identification were not considered in the present work. For immature stages found during field surveys, species identification was performed on third-instar larvae using external characters following Hůrka (1975) and Franciscolo (1997), considering the observations reported by Scaccini (2015). Pupae were reared to the adult stage to validate species identification.

Figure 2.  

Habitus of Platycerus caprea adults collected in Italy. a Male, Vercelli Province, Alagna Valsesia, 16.VI.2012; b Male, Bergamo Province, Zambla, 19.X.1969; c Male, Bergamo Province, Zambla, 19.X.1969; d Female, Bergamo Province, Zambla, 19.X.1969; e Magnification of the head, specimen in (a); f Magnification of the head, specimen in (b); g Magnification of the head, specimen in (d); h Male genitalia, specimen in (b); i Female styli, specimen in (d). Photo credit: M. Zilioli.

Figure 3.  

Habitus of Platycerus caraboides adults collected in Italy. a Male, Alpi Cozie, Val di Susa (collection date is not available); b Male, Bolzano Province, Tires, 11.VI.2010; c Male, Piacenza Province, Ferriere (surroundings), 8.V.1969; d Female, Bergamo Province, Piazzolo, 14.VIII.2013; e Magnification of the head, specimen in (a); f Magnification of the head, specimen in (c), re-pinned; g Magnification of the head, specimen in (d); h Male genitalia, specimen in (a); i Female styli, specimen in (d). Photo credit: M. Zilioli.

Data analysis