Systematic review of the firefly genus Scissicauda (Coleoptera, Lampyridae, Amydetinae) from Brazil

Abstract The Amydetinae genus Scissicauda McDermott, 1964 is reviewed and redescribed. We describe Scissicauda balena sp. n. from Brazil as new, and provide illustrations of the structural features and a key to species of both sexes.


Introduction
The subfamily Amydetinae is a little known firefly group distributed predominantly in South America. Molecular data identified Lampyrinae as sister to Amydetinae (Bocakova et al. 2007, Viviani 2011, Amaral et al. 2014, though the circumscription of the subfamily remained unaddressed due to limited taxon sampling of the studies. Phylogenetic relationships of Amydetinae genera sensu McDermott (1966) has not been clarified yet. The monophyly of Amydetinae has been challenged by Jeng (2008, unpublished), whose analyses involved morphological characters, concluding that the subfamily is polyphyletic.
Most Amydetinae share a complex antennal morphology in the males, except some species of Vesta, whose antennae are often serrate. Most of the females remain undescribed. McDermott (1966) assigned Amydetinae to subfamily level, keeping its subgroups as subtribes: Amydetina, Vestina and Psilocladina, the latter with five genera including Scissicauda. He supposedly retained these subtribes under Amydetini, although not explicitly quoting this tribe in his catalogue (1966). Though such Psilocladina has been challenged (Jeng 2008, unpublished), we refer to McDermott (1966) subdivisions as to the latest comprehensive study. McDermott (1964) established Scissicauda as a replacement name for the monotypic Schistura Olivier, 1911 because it was preoccupied by a balitorid fish genus, Schistura McClevelland, 1838(cf. McDermott 1966. Scissicauda is easily distinguishable from all other lampyrids by the strongly indented pygidium. Currently, only males of the type species, S. disjuncta (E. Olivier, 1896), from Rio de Janeiro, Brazil are known. Here we present a review of the genus, redescribe the type species S. disjuncta, and provide the female description for the first time, together with phenological data for a population in the Serra dos Órgãos Mountain Range (Rio de Janeiro, Brazil). We also propose Scissicauda balena sp. n. as new and provide a key to species of the genus.

Material and methods
The holotype of S. disjuncta was loaned from the Natural History Museum in Paris (MNHN, A. Taghavian). Other specimens were examined in the Museu de Zoologia de São Paulo, São Paulo, Brazil (MZSP, S. Casari) and Museu Nacional do Rio de Janeiro, Rio de Janeiro, Brazil (MNRJ, M. L. Monné). Additional specimens of S. disjuncta were obtained in the Serra dos Órgãos mountain range (Teresópolis municipality, Rio de Janeiro State, Brazil), using monthly sampled Malaise traps (flight interceptor), arranged in seven transects along an elevation gradient in 850-2030m, separated by approximately 200m distance. Totally, 84 Malaise traps were installed there and operated for a one year period (06/2013-06/2014). Specimens were stored in 92% ethanol and are housed at Coleçao José Alfredo Pinheiro Dutra, Universidae Federal do Rio de Janeiro (DZRJ, J. R. Mermudes). The specimens of Scissicauda balena sp. n. were loaned from The Natural History Museum, London (BMNH, M. Geiser).
Terms for structural features follow Jeng et al. (2011), Zaragoza (1995 and Silveira and Mermudes (2013, 2014a, 2014b; Crowson (1938Crowson ( , 1944 for metendosternite nomenclature; and Kazantsev and Perez-Gelabert (2008) for female genitalia. For taxonomic treatment we follow McDermott (1966), which is the most recent species catalogue of Lampyridae. Specimens had the abdomen dissected and boiled in 10% KOH. This clearing procedure was also applied to two entire specimens of the type species. The morphology was examined using a stereomicroscope and photographs were made with the Leica Application Suite CV3 Auto-montage Software.
Remarks. Concerning the etymology for the generic name, McDermott (1964) did not refer explicitly to the meaning of Scissicauda, neither did Olivier (1911) for Schistura. Scissi is putatively derived from the English word scissor, which in turns refer to the old French cisoires and the Latin caedo, caesus; and cauda, a Latin word for the pygydium (Brown, 1956) (see Figs 30,32). Scissicauda is of a feminine gender.
Biology. Active during daytime, on moisty days. In our experimental design (Jun/2013-Jun/2014), individuals were only collected between December and February, when there is a local increase in pluviosity (Graphic 1). Our results suggest that S. Graphic 1. For the period of Jun/2013-Jun/2014, S. disjuncta was sampled at 1250m of elevation and had an abundance peak in the rainy season, between the November-February in the Serra dos Órgãos mountain range. disjuncta breeds during the rainy seasons, possibly in low montane forests. Otherwise, although it could in principle be a sampling artifact, it could also mean that the species has a patchy distribution.
Remarks. McDermott (1966:87) quoted Lychnuris disjuncta referring it to Olivier 1899: 91, but in this paper there is no reference to such a name. However, on page 90, there is a Lychnuris adjuncta Olivier, 1899, which is not quoted under Lychnuris in his catalogue (McDermott 1966). Therefore we consider the citation a quid pro quo. Regarding the etymology of the specific name, the author did not mention a meaning for disjuncta, which is a Latin expression for apart, separate. We tentatively associate it with the separated corners of the pygidium. Diagnosis. Males with antennal lamellae absent (Fig. 54) (present in S. disjuncta, Fig. 10), anterior pro and mesoclaws entire (bifid in S. disjuncta), phallus dorsal plate subtruncate basally, phallic groove at half of its length, moderately curved (strongly rounded basally, phallic groove at apical one third, strongly curved in S. disjuncta); ventral plate at least 2× phallobase length (slightly shorter than phallobase in S. disjuncta); parameres ventrobasal process digitiform, extending slightly beyond ventral plate, shorter than paramere itself (Figs 63-66) (process rudimentary in S. disjuncta, Figs 36-41). Females with sternum VIII rounded (Fig. 68) (constricted at posterior one third, indented medially in S. disjuncta, Fig. 43).
Etymology. The specific name balena is a Latin expression for whale, whose tail resembles the pygidium of this species. The name is formed as a noun in apposition.
Finally, S. disjuncta share remarkable similarities on reproductive morphology with some taxa considered basal amongst the Lampyridae (Bocakova et al. 2007, Stanger-Hall et al. 2007), such as: some Photurinae taxa, e.g. Presbyolampis spp. (cf. Kazantsev and Perez-Gelabert 2008), and Photuris (cf. Rosa 2007 for male genitalia; L. Silveira dissected some females of this genus); as well as some Luciolinae taxa (reviewed by Ballantyne 1987), especially for the female internal genitalia, that of S. disjuncta being quite similar to Luciola Laporte, 1833 (South et al. 2008) and Aquatica Fu et al. 2010(Fu et al. 2012, although lacking bursa and median oviduct plates. Even though its knowledge is still incipient, future phylogenetic evaluation and functional morphology of the firefly female genitalia would certainly enhance lampyrid taxonomy.

Sexual dimorphism
We describe for the first time the females of Scissicauda disjuncta and S. balena sp. n., detailing especially the female internal tract, which is inedit for South American taxa and also for the Psilocladina as a whole. Other psilocladina taxa with known females are Psilocladus Blanchard, 1846 and Pollaclasis Newman, 1838, both genera showing virtually no secondary sexual dimorphism. In Scissicauda, secondary sexual dimorphism is stronger in S. disjuncta, where only the males have long lamellae and teethed pro and mesoclaws. S. balena sp. n. is dimorphic only in abdominal segments VIII and beyond. Besides the slightly greater size of the females in both Scissicauda species, there are no other noteworthy dimorphic character.

Sexual selection and possible function of the pygidium in the genus
We suggest male pygidium is involved in reproduction. This could be either working as a clamp, or by enhancing female fecundity. Clamping structures allow prolonged copulation, which is generally assumed to ensure paternity by preventing other males to accessand thus fertilize the eggs of the female (Wing et al. 1993). The evidence that male pygidium may work as a clamp is that anterior angles of female pygidium, which should attach male abdomen, are sclerotized. Alternatively, male reproductive structures may stimulate females while mating, and thus increase fertilization and/or oviposition rates. It was shown that in polyandric systems, female choice can promote male genitalic diversification (Arnqvist 1998), although the modus operandi is still disputed (Hosken and Stockley 2004). Furthermore, structures involved in mating are generally species-specific (which is the case in Scissicauda) and evolve fast (Eberhard 2004), often as a consequence of sexual selection (Hosken and Stockley 2004), and may promote reproductive isolation either by structural or sensory lock-and-key, thus avoiding hybridization (Masly 2012). Future field observations and detailed histological studies would be useful to test these hypotheses.

Endemism
Although similar sampling efforts have been made in other montane areas of the Rio de Janeiro State (notably the Serra da Mantiqueira formation), Scissicauda was only collected in the Serra dos Órgãos (Petrópolis and Teresópolis municipality). However, the holotype of S. disjuncta is reported from Rio de Janeiro (Olivier 1896), which could be related to the city or the state (which includes the aforementioned municipalities). Thus, we assume that S. disjuncta is restricted to the Serra dos Órgaos low montane forests, and could have occurred also in the Tijuca Forest, although no specimens collected there were found in any of the entomological collections studied. S. balena sp. n. is described from Espírito Santo State, Brazil, lacking more precise locality data.