Rhizotrogus genei Blanchard, 1851

Sabatinelli, Guido, Cillo, Davide & Bazzato, Erika, 2025, Rhizotrogus ruzzantei, a new species from southwestern Sardinia (Italy), with biogeographic considerations on the Sulcis-Iglesiente subregion and Scarabaeoidea endemics of Sardinia (Coleoptera: Scarabaeidae: Melolonthinae: Rhizotrogini), Zootaxa 5665 (2), pp. 256-270 : 258-259

Rhizotrogus genei Blanchard, 1851 (restored combination)

Figures 1, 4

Rhizotrogus insularis Reiche, 1862

Geotrogus sardous Burmeister, 1855

Type material examined. Rhizotrogus genei Blanchard, 1851 . Syntype 1 ♂ ( MNHN): Museum Paris / Sardaigne / Géné 1836 // Rhizotrogus / Genei Blanch. / type // R. Genei / Cat. Mus. / Piemont / M.Géné // Type (red label). Geotrogus sardous Burmeister, 1855 . Syntypes 1 ♂ and 1 ♀ ( ZNSH): Sardous / Nob. [nobis means Burmeister is the author of these names] / Sardin—Sp. // (white label, black margin line).

Additional material examined. Italy, Sardinia, Sassari province: Torralba, Monte Oes , 6.III.1994, A.Lecis leg. 1 ♂ ALMC ; Bunnari, 1.I.1962, 1 ♂ UNSS . Chilivani, 30.I.1971, A.Franzini leg. 3 ♂♂ MHNG ; 29.II.1971, A.Franzini leg. 2 ♂♂ MHNG ; 25.II.1971, A.Franzini leg. 1 ♂ MHNG ; Uras, 22.I.1970, F.Cassola leg. 1 ♂ MHNG . Nuoro province: Campeda , 1.III.1964, 1 ♂ UNSS ; 12.I.1966, 2 ♂♂ UNSS . Oniferi, 25.I.1966, 1 ♂ UNSS ; Ottana, 14.III.1975, 2 ♂♂ UNSS ; 25.II.1976, 2 ♂♂ MHNG ; 28.XI.1976, 1 ♂ 1 ♀ MHNG ; Gairo, Taquisara, Monte Sasso Orruda , 1027m , 14.II.1993, M.G.Atzori leg. 1 ♂ MGAC ; Piana di Oliena , II1994, D.Cillo leg. 1 ♂ DCCC . Oristano province: Isola Mal di Ventre , Oristano , 22.I.1969, 1 ♂, DCCC . Terralba, 10.X.1987, 1 ♂ UNSS . “ Città Metropolitana di Cagliari ” province: Villasimius, Capo Carbonara , 60m , 17.XII.2014, C.Ancona leg. 3 ♂♂ MHNG ; Dolianova, I.1991, D.Cillo leg. 3 ♂♂ DCCC ; II.1985, D.Cillo leg. 5 ♂♂ DCCC ; Elmas, 15.I.2006, F.Fois leg. 2 ♂♂ DCCC ; Elmas, 29.XII.2011, F.Fois leg. 3 ♂♂ DCCC ; 22.XII.2011, F.Fois leg. 3 ♂♂ DCCC ; Monserrato, 24.II.2016, D.Piras leg. 1 ♂ ALMC . Quartu Sant’Elena, Flumini, 19.XII.2017, R.Rattu leg. 2 ♂♂ AMMC ; 2 ♂♂ MHNG ; 22.XII.2000, D.Cillo leg. 4 ♂♂ DCCC ; 1-20.I.2009, A.Cardilloni leg. 2 ♂♂ MHNG ; Foxi, 11.XII.2010, E.Bazzato leg. 1 ♂ DCCC ; XII.2011, E.Bazzato leg. 1 ♂ DCCC ; Porticciolo, 2.III.2003, D.Cillo leg. 1 ♂ DCCC ; 4.I.2001, D.Cillo leg. 1 ♂ DCCC ; 5.I.2000, D.Cillo leg. 1 ♂ DCCC ; 9.III.2002, D.Cillo leg. 1 ♂ DCCC ; 17.I.2002, D.Cillo leg. 3 ♂♂ DCCC ; 20.III.2003, D.Cillo leg. 1 ♂ DCCC ; 21.I.2002, D.Cillo leg. 1 ♂ DCCC ; III.2003, D.Cillo leg. 3 ♂♂ DCCC ; XII.2002, D.Cillo leg. 2 ♂♂ DCCC ; Sa Funtanedda, 4.I.1988, M.Murgioni leg. 1 ♂ MGAC ; 4.I.1988, M.G.Atzori leg. 1 ♂ DCCC ; 9.I.1990, M.G.Atzori and M. Murgioni 2 ♂♂ MGAC ; 11.I.1999, M.Murgioni leg. 1 ♂ MGAC ; 13.II.1999, M.Murgioni leg. 1 ♂ MGAC ; 14.XII.1997, M.G.Atzori and M.Murgioni leg. 1 ♂ MGAC ; 15.II.1989, M.G.Atzori leg. 1 ♂ DCCC ; 23.I.1989, M.Murgioni leg. 1 ♂ MGAC ; 23.I.1989, M.G.Atzori leg. 4 ♂♂ DCCC ; 23.I.1999, M.Murgioni leg. 1 ♂ MGAC ; 24.II.1989, M.G.Atzori leg. 1 ♂♂ DCCC ; III.1999, M.G.Atzori leg. 2 ♂♂ ALMC ; 2.II.2000, M.G.Atzori and M. Murgioni leg. 3 ♂♂ MGAC ; 10.I.2001, M.G.Atzori leg. 3 ♂♂ MGAC ; 2.II.2001, M.Murgioni leg. 1 ♂ MGAC ; 6.II.2002, M.G.Atzori leg. 1 ♂ MGAC ; III.2002, M.Murgioni leg. 1 ♂ 1 ♀ MGAC ; 29.XII.2002, M.G.Atzori leg. 1 ♂ MGAC ; 25.I.2005, M.G.Atzori leg. 3 ♂♂ MGAC ; I.2009, M.Murgioni leg. 2 ♂♂ MGAC ; II.2014, M.G.Atzori leg. 1 ♂ MGAC . Pula, Is Molas, X.2016 L.Fancello leg., 1 ♂ DCCC . Cagliari, Molentargius , 15.I.2015, R.Rattu leg. 1 ♂ DCCC . Cagliari, Saline di Stato , 10.I.2014, E.Bazzato leg. 2 ♂♂ EBQE . Assemini, Flumini Mannu, 25.XI.2021, L.Fancello leg. 2 ♂♂ LFCC . “ Sud Sardegna ” province: Domusnovas, Sa Duchessa , X.2022, L.Fancello leg., 1 ♂ LFCC ; Giara di Gesturi , 28.12.2022, L.Fancello leg. 1 ♂ LFCC ; Arbus, Piscinas, Portu Maga , 25 m , 8.XI.2009, D.Sechi leg., 3 ♂♂ JMCH ; San Sperate, 19.II.2016, D.Sechi leg. 2 ♂♂ AMMC ; 9 ♂♂ MHNG ; 20.II.2016, D.Sechi leg., 1 ♂ EBQE ; 9 ♂♂ MHNG ; 20.II.2016, D.Sechi leg., 9 ♂♂ DCCC ; 19.II.2016, M.G.Atzori and D.Murgioni leg. 6 ♂♂ MGAC ; Serrenti, Monti Mannu, 11.XII.2024, L.Fancello leg. 1 ♂ LFCC . Sant’Anna Arresi, Porto Pino, env. Foxi, 17.I.2020,

M.G.Atzori leg. 1 ♂ MGAC; Isola di Sant’Antioco, Coaquaddus beach, 24.III.1996 , M.G.Atzori leg. 1 ♀ MGAC; 1.IV.2021 , L.Fancello leg. 1 ♂ DCCC; 1.IV.2021 , L.Fancello leg. 2 ♂♂ LFCC; Nuraghe Feminedda , 16.II.2025 , L.Fancello leg. 1 ♀ LFCC. Turri , 27.XII.2010 , L.Fancello leg. 1 ♀ LFCC; Porto Botte , XII.2010 , L.Fancello leg. 1 ♀ LFCC; Pabillonis , Is Arenas, 12.III.1969 , F.Cassola leg. 2 ♂♂ MHNG. Escalaplano , XI.1970 , 1 ♀ MHNG; Carbonia , Monte Sirai, III.2021 , L.Fancello leg. 1 ♂ LFCC; Tuscany Islands : Capraia, 5.X.1974 , P.Brignoli leg. 1 ♂ MHNG (sub R. insularis Reiche, 1862 ). France, Corsica: (without more precise location) Damry leg. 2 ♂♂ MHNG; Reitter, 1 ♂ MHNG .

Taxonomic discussion. Rhizotrogus genei ( Fig. 1 ) was described by Blanchard in 1851 from “ Piémont ” a designation that reflects the historical political context of the time. During that period, Sardinia was part of the Regno di Sardegna ( Kingdom of Sardinia 1720–1861), which included both the island of Sardinia and several mainland possessions in western Italy. The kingdom was often referred to as the Kingdom of Piedmont, as the island itself held a secondary role within the monarchy. This historical background justifies the indication of “ Piémont ” on the labels of the type specimen .

Reitter (1902) included R. euphytus Buquet, 1840 as well as R. genei in the Apterogyna species group at the subgeneric level within Rhizotrogus Latreille, 1825 crediting Apterogyna to Reiche (1882) who however did not describe it formally. Marseul (1878) described three Apterogyna species, and could be the most suitable author for this species group name. Moreover, Reitter’s concept of the genus Apterogyna — it disagrees with the sentence above (subgeneric level of Apterogyna is stated here for the same paper) encompassed species in which males are winged and females apterous. However, in genei , both sexes are fully winged, which disqualifies it from this genus based on Reitter’s own definition. Burmeister (1855) redescribed Rhizotrogus genei as Geotrogus sardous without a more precise locality than Sardinia. Paulian (1959) reported genei for both Sardinia and Corsica under the name Rhizotrogus insularis Reiche, 1862 . Baraud (1977) clarified that R. insularis and R. genei were synonyms. He also pointed out that the name Apterogyna , credited to Reiche (1892), was preoccupied by a homonymous genus established by Latreille (1809) for a group of Hymenoptera. Given that females of genei are winged, Baraud placed the species in Rhizotrogus sensu stricto, where it remained until the revision by Coca-Abia & Martín-Piera (1998) and confirmed by Coca-Abia (2003). These authors argued that in Rhizotrogini , apterism and associated morphological features—such as the position of the median and posterior coxae, and the development of the humeral callus—are adaptations to desert environments. Emphasizing other characters, particularly male and female genital morphology, they synonymized Apterogyna Reitter, 1902 and Pseudoapterogyna Escalera, 1914 (replacement name for Apterogyna ) with Geotrogus Guérin-Méneville, 1842 , and consequently placed genei within Geotrogus .

This classification was followed in Ballerio et al. (2014) and species catalogued in the genus Geotrogus by Bezděk (2016). We feel the placement of genei in Geotrogus unsatisfactory since the characters used by Coca-Abia & Martín-Piera (1998) and by Coca-Abia (2003) to define the Geotrogus cluster do not adequately reflect the true morphology of the species genei . In our assessment, the species shows stronger affinities with Rhizotrogus sensu stricto, warranting its reattribution to this genus. In their study, Coca-Abia & Martín-Piera (1998) dismissed characters such as wing development (micropterism) in both sexes—as well as associated morphological changes like the length of the coxae and the development of the humeral callus—as adaptive features, rather than diagnostic ones. Actually in these studies, the genus Geotrogus was defined on a limited set of characters and number of species (see Coca-Abia 2003, Table 1): an antennal club shorter than the stem and of similar size in both sexes; weakly serrated lateral margins of the pronotum; hind tibiae slightly punctate and shiny; and parameres as long as or longer than the phallobase. We have tested these morphological criteria on a large series of genei specimens and challenge this interpretation. In males, the antennal club is approximately equal in length (2.4 mm) to the “stem”, if the stem is defined as the funicle alone. In females, however, the antennal club is markedly shorter (0.8 mm), consistent with other Rhizotrogus species. This marked sexual dimorphism contradicts the claim of equal antennal size between sexes in Geotrogus .

Furthermore, the lateral pronotal margins in genei are clearly serrated, as also observed in R. marginipes Mulsant, 1992 ; R. maculicollis Villa & Villa, 1833 ; R. romanoi Sabatinelli, 1975 ; R. cicatricosus Mulsant, 1842 ; Firminus fossulatus (Mulsant & Rey, 1859) ; and G. euphytus . Regarding the aedeagus, the parameres in R. genei are shorter (2.4 mm) than the phallobase (2.7 mm), whereas in R. romanoi and R. cicatricosus , for example, the parameres are at least equal in length to the phallobase. Sparacio (2014) also rejected the synonymy of Pseudoapterogyna with Geotrogus , but without providing any supporting arguments. It is evident that the morphological analysis and the resulting phylogenetic framework proposed by Coca-Abia and collaborators is far from satisfactory and requires reinforcement through molecular studies, which are now easier to perform. We do not aim here to provide a full critical review of the works by Coca-Abia & Martín-Piera (1998) and Coca-Abia (1999, 2003), but rather to highlight specific points of concern regarding the taxonomic placement of R. genei Blanchard, 1851 and the newly described species within the genus Rhizotrogus .

Figures

FIGURES 1–7. Habitus of 1) Rhizotrogus genei Blanchard, 1851 ♂ specimen from Cagliari; 2) R. ruzzantei sp. nov. holotype ♂; 3) R. ruzzantei paratype ♀. Pronotum lateral view: 4) R. genei ♂; 5) R. ruzzantei ♂. Left wing: 6) R. ruzzantei ♀; 7) R. ruzzantei ♂ (scale line = 2.5 mm).