The genus Cephennium P.W.J. Müller & Kunze (Staphylinidae, Scydmaeninae, Cephenniini) currently encompasses more than 160 species (Orousset, 2017). Most of the species occur in the western Palaearctic region (Orousset, 2017) and only nine are known in North America. The North American fauna is represented by eight endemic species in California and one adventive European species until now known only from Nova Scotia, Canada (Maja & Klimazsewski, 2004; Hopp & Caterino, 2009; Orousset, 2017). Two species, Cephennium thoracicum (P.W.J. Müller & Kunze, 1822) and Cephennium gallicum Ganglbauer, 1899 were recently collected in Montreal (QC, Canada). These collections correspond to the first records in North America for C. thoracicum and for the province of Quebec for C. gallicum.
Until now, the single Cephennium species known in Canada (NS) was C. gallicum, reported by Majka and Klimaszewski (2004). Because it is not possible to identify Cephennium species with certainty from females, it was decided that only male specimens would be examined and cited. The specimens were identified mostly based on male genitalia and using the Orousset (2017) key to species. In addition, males of C. thoracicum (Fig. 1a) can be externally distinguished from C. gallicum by the presence of a notch at the apex of the protibia (Orousset, 2017). The male genital structures being ventrally visible by the transparency of the abdomen, the sex of living specimens can be easily identified by holding them on their back using a small wet brush. Subsequently, examination of the protibiae of the males made it possible to differentiate the two species. Male genitalia of C. thoracicum also present two developed and symmetric copulatory structures (Fig. 1b) which are also visible by transparency.
Amazingly, several dozen specimens of C. thoracicum were observed during the various collection campaigns but only one (male) specimen of C. gallicum was collected. In their work, Majka and Klimazweski (2004: 3) mention that Cephennium species are usually collected from leaf litter and rotten wood, notably in deciduous forests. The site where these specimens were collected is located at the base of the Mont-Royal, in Montreal (QC, Canada). They were collected in leaf litter in degraded slopes of a disturbed grove of deciduous trees. Species of this genus are known to feed on oribatid mites (Majka and Klimazweski, 2004; Jałoszyński & Beutel, 2012; Jałoszyński and Olszanowski, 2016). The leaf litter where the specimens were found contained large quantities of these mites and several of the beetles were observed consuming them.
Majka and Klimaszweski (2004) evoke the presence of the port of Halifax to explain the presence of C. gallicum in the city. The fact that Montreal is also an important river port could have helped the introduction of these species there. As noted in previous works, the Montreal site where the two Cephennium species were collected has already brought several introduced species, newly recorded for Canada: Bipalium adventitium (Platyhelmintida, Geoplanidae), Loricula coleoptrata (Heteroptera, Microphysidae) and Anommatus duodecimstriatus (Coleoptera, Teredidae) (Justine et al., 2019; Théry, 2022; Théry & Ratzlaff, 2022). It is suspected that the presence of these species in this area could be explained by the presence of two cemeteries (Mont-Royal cemetery and Notre-Dame-des-Neiges cemetery) in the surroundings (Théry, 2022; Théry & Ratzlaff, 2022). Bipalium adventitium and Anommatus duodecimstriatus are known to be transported with soil notably with potted plants. Females of Loricula coleoptrata live in leaf litter, a biology which could help their transportation. As Cephennium species also live in leaf litter and humus, this hypothesis could be also proposed in their cases.
The author acknowledges Christian Perez (Istres, France) for his help in the bibliographic research; Alfred Newton (Field Museum of Natural History, Chicago, USA) and Anthony Davies (Canadian National Collection of Insects, Arachnids and Nematods, Ottawa, Canada) for the information about the distribution of the genus Cephennium in Canada and in the USA; Colin Favret (Université de Montréal, Montreal, Canada) for his advice and the use of microscopic equipment in his lab; Maxim Larrivée and Stéphane Le Tirant (Insectarium de Montréal, Montreal, Canada) for their support.
Müller P.W.I., Kunze, G., 1822. Monographie der Ameisenkäfer (Scydmaenus Latreille).Schriften der Naturforschenden Gesellschaft zu Leipzig, 1: 175-204.
Fig 1. - Dorsal habitus of Cephennium thoracicum (a), specimen CNC480414 (scale 200 μm); male genitalia of C. thoracicum (b), specimen CNC480413, and of C. gallicum (c), specimen CNC480412 (scale 100 μm).
