Notes on Stenhelmoides and description of the true male genitalia of S. strictifrons Grouvelle, 1908 (Coleoptera: Elmidae)

ABSTRACT The genus Stenhelmoides comprises 15 species spread over all Central and South America and its greatest species richness is clearly associated with Amazonian regions. Based on examination of type specimens and additional material, we describe and illustrate the true male genitalia of Stenhelmoides strictifrons, which had until now been incorrectly illustrated in the literature. We also report new records of the genus Stenhelmoides from Brazil and Guyana. In addition to pictures of the species’ habitus, we provide pictures of the type specimens of Stenhelmoides grandis, S. grouvellei, S. guyanensis; S. strictifrons and S. submaculus. Based on the International Code of Zoological Nomenclature, we recognize additional paralectotypes for S. guyanensis and for S. grouvellei.


INTRODUCTION
Elmidae Curtis, 1830 is a cosmopolitan family of Coleoptera with around 1503 known species distributed in 151 genera Short 2018). The family has its greatest richness and abundance in the Neotropical region (Jäch and Balke 2008) and, as expected, the Amazonian elmid fauna is very diverse.
The genus Stenhelmoides Grouvelle, 1908 comprises 15 species distributed throughout the Neotropical region, from Mexico to Paraguay . Despite being more likely associated with Amazonian regions, where most of the known species can be found, the genus seems to potentially occur in many kinds of Neotropical biomes. Grouvelle (1908) described Stenhelmoides based on two species, Stenhelmoides strictifrons and Stenhelmoides guyanensis from French Guiana (Rivière Lunier, Tumuc Humac), but without designating a type series, nor did he mention the number of specimens examined for either species. Delève, in the 1960s, examined Grouvelle's collection and designated types for many species, including the "holotype" for S. strictifrons, based on a female specimen (Spangler and Perkins 1989). Despite having labelled the specimen, Delève (1970) did not include this information in his subsequent publication about S. strictifrons. Finally, Spangler and Perkins (1989) revised the genus Stenhelmoides, and redescribed all known species, including S. strictifrons. They also chose a male from Grouvelle's collection, labeled similarly to the "holotype", to include in the type series as a paralectotype. They described and illustrated its genitalia.
After carefully checking specimens of Stenhelmoides strictifrons from many localities of Brazil and examining the type specimens (lectotype and paralectotype) housed in the Muséum National d'Histoire Naturelle, Paris, we concluded that the male genitalia of the species was incorrectly illustrated by Spangler and Perkins (1989). To rectify the morphological descripttion of the species and avoid potential errors by other researchers when trying to identify Stenhelmoides species, we describe and illustrate the correct male genitalia of S. strictifrons.
We also report new records for Stenhelmoides beebei Spangler andPerkins, 1989, Stenhelmoides stegastus Spangler andPerkins, 1989, Stenhelmoides strictifrons Grouvelle, 1908, Stenhelmoides platysternum Spangler and Perkins, 1989, and Stenhelmoides variabilis Spangler and Perkins, 1989 in Guyana. These are the first records for Stenhelmoides in the Brazilian states of Amapá, Bahia, Minas Gerais, Roraima and Tocantins. For the first time, habitus photographs of type specimens of the following species are provided: Stenhelmoides grandis Spangler and Perkins, 1989, Stenhelmoides grouvellei Pic, 1923, Stenhelmoides guyanensis Grouvelle, 1908, S. strictifrons Grouvelle, 1908, and Stenhelmoides submaculus Hinton, 1937 Based on examination of the type series housed in the collection of the Muséum National d'Histoire Naturelle, Paris and following information provided in Spangler and Perkins (1989), Monte and Mascagni (2016), and Polizei and Casari (2019), we recognized one type specimen of S. guyanensis as a paralectotype and several paralectotypes of S. grouvellei.

MATERIAL AND METHODS
The material studied came from different Brazilian and international collections (listed below). Species level identifications were made using the taxonomic key of Spangler and Perkins (1989), original species descriptions and examination of type material. A Leica MS5 (Wetzlar, Germany) stereoscopic microscope was used for morphological studies and a Canon EOS550D (Tokyo, Japan), attached to a Leica N205A (Wetzlar, Germany) stereoscopic microscope, was used to photograph the specimens. Images were treated on Combine ZM and Adobe Photoshop.
For examination of male genitalia, the aedeagi were extracted from the specimens, cleared in heated 10% KOH for five minutes (Brown 1972) and mounted on temporary slides with glycerin. Pictures were taken with the aid of a light microscope Nikon model Eclipse E200 (Tokyo, Japan), equipped with BIOPTIKA CMOS-10.0. Drawings were made on Camara Lucida and digitalized on Adobe Illustrator. Dissected genitalia were stored in microvials with glycerin attached to the same pin as the specimen.
The general morphological terminology follows . Specimen labels are quoted verbatim. Change of lines are indicated by "/" and different labels are separated by "//". Localities followed by "*" represent new records.
The following collections were visited and/or contain deposited specimens (

Diagnosis. (Modified from Spangler and Perkins 1989)
Stenhelmoides strictifrons can be distinguished from all species of Stenhelmoides by its small size (2.04 -2.52 mm), the dorsal plastron pattern on the pronotum, the metaventrite being slightly depressed, the elytral granules organized in rows, the absence of hair-like setae tufts on tarsi and the male genitalia with the apical surface of the parameres and median lobe densely covered with spine-like setae (Figures 1c-e).

Male genitalia. Phallobase (Figures 1c, d) broad and short.
In dorsal view, 1.3 times broader at base than parameres and three-fifths their length. Parameres (Figures 1c-e) as long as median lobe. In dorsal view (Figures 1c-d) not tapering to apex, slightly curved toward median lobe, apices feebly invaginated on internal lateral margin, rounded and covered with distinct spine-like setae over apical one-fifth. In lateral view (Figure 1e) dorsal margin nearly straight, ventral margin sinuous, apex rounded, spine-like setae concentrated on apical

New records
Stenhelmoides beebei Spangler and Perkins, 1989 (Figure 2a Spangler & Perkins, 1989 (MZSP 42711); E-F − S. stegastus Spangler & Perkins, 1989 (INPA); G-H − S. variabilis Spangler & Perkins, 1989 (CZMT-CEMT000008175). Scale bar = 0,5 mm. This figure is in color in the electronic version. without identification and two misidentified as S. strictifrons by Deléve in 1966). Spangler and Perkins determined all specimens as S. grouvellei. These three conspecific specimens were from French Guiana [very old labels]. Spangler and Perkins treated the specimen bearing the type label as the "holotype" (see Spangler and Perkins, 1989:42) designating it as the lectotype for Stenhelmoides grouvellei and the other three remaining specimens as paralectotypes (ICZN 1999, Art. 74.6). In 2017, T.T.S. Polizei found the lectotype and just one of the two paralectotypes examined by Spangler and Perkins (1989) at the MNHN. Based on the similarity of the labels and the observations of Spangler we confirmed that this specimen is one of the syntypes from Pic (1923) and is therefore a paralectotype.

Condition:
The paralectotype is glued on a card and it is in perfect conditions. There are no missing parts and the female genitalia are still preserved in the specimen. Comments: In the original description of the species, Grouvelle (1908) based the species on the five specimens from Rivière Lunier et Bas-Carsevenne. However, in their revision, Spangler and Perkins (1989) studied Grouvelle's collection housed at MNHN and found just two specimens labeled as "Stenhelmoides guyanensis" by Deléve. One of these is not conspecific with the species, and Spangler and Perkins regarded it as a new species [this exemplar is one of the paratypes of S. grandis Spangler and Perkins, 1989, Figure 3a]. The other specimen (a female) was designated as the lectotype  Spangler & Perkins, 1989 [Paratype]; B − S. grouvellei (Pic, 1923) [Paralectotype]; C − S. submaculus Hinton, 1937 (BMNH010584113) [Paratype]; D − S. guyanensis Grouvelle, 1908 [Paralectotype]; E − S. strictifrons Grouvelle, 1908 [Lectotype]. Scale bar = 0,5 mm. This figure is in color in the electronic version.
by Spangler and Perkins (1989). During a visit to the MNHN in 2017, T.T.S. Polizei found another specimen with the same data as the lectotype and also determined as "Stenhelmoides guyanensis" by Deléve in 1967. There is no doubt that this specimen is one of the specimens that Grouvelle reported as "5 exemplars" in the original description. Besides, this species has the pronotum distinct, without granules on the disc, a condition unique among all the species of Stenhelmoides. This syntype is herewith recognized as paralectotype.

Condition:
The lectotype is glued on a card and it is slightly damaged. Missing parts include the apical tarsomeres and claws on the right hind leg. Ventrites I-V and the female genitalia are glued to a card pinned below the specimen.

DISCUSSION
Despite the very careful revision, for some unknown reason, Spangler and Perkins (1989) incorrectly illustrated the male genitalia of S. strictifrons. The error was first noticed in 2011 by A.S. Fernandes while examining the male (paralectotype) of S. strictifrons from Grouvelle's collection housed in the MNHN. Fernandes also discovered that Stenhelmoides specimens from different regions in Brazil he had already determined as a new Stenhelmoides species (based on the very distinct male genitalia) were actually specimens of S. strictifrons. Later, A.S. Fernandes and T.T.S. Polizei examined several specimens of S. strictifrons, including the lectotype (female), to confirm that the male genitalia clearly differed from those shown in Spangler and Perkins (1989).
Despite being widespread in the Neotropics and very conspicuous due to its large size, characteristic body shape and plastron pattern (Spangler and Perkins 1989;González-Córdoba et al. 2020), Stenhelmoides is poorly represented in collections. Moreover, the genus is mainly known from light-trapped specimens and its larva was only discovered a few months ago (González-Córdoba et al. 2020). Most of the extant bionomic information on Stenhelmoides is provided by Spangler and Perkins (1989), who did not describe special habitat preferences or conditions associated with the specimens. Based on Spangler and Perkins (1989), Stenhelmoides specimens may be found in a variety of substrates and in different kinds of Neotropical streams. Nevertheless, during our several collections in various parts of Brazil, they were not easily found. From all the material examined in this work, only the two S. strictifrons specimens from Goiás state, Brazil (see Barbosa et. al. 2013) came from aquatic samples.

CONCLUSIONS
The male genitalia are one of the main morphological structures for species determination in many beetle families (Crowson 1981) and Elmidae are no different. Stenhelmoides strictifrons is the most common and widespread species of the genus in Brazil and the miss-illustrated male genitalia was a barrier to the species determination, especially for local researchers without easy access to the type specimens. By correctly illustrating the male genitalia, we enable accurate species identification for S. strictifrons. Currently, Stenhelmoides is reported from 15 countries across the Americas (Spangler and Perkins 1989;Jäch et al. 2016;González-Córdoba et al. 2020). Here we provide four new species records for the genus in Brazil, making Brazil one of the most diverse countries for the genus, alongside Venezuela, with seven known species . We also increase the known distribution of Stenhelmoides in Brazil to eleven states (previously known from six), representing four of the five Brazilian geographical regions (North, Northeast, Midwest and Southeast) and three of the six Brazilian biomes (Amazon, Atlantic rainforest and Brazilian savanna) (IBGE 2019). Finally, we provided updates to the original descriptions, photographs of all Stenhelmoides species known from Brazil and valuable photographs of the type specimens for the five species to which we had access. This additional information is an important supplement to the literature, especially concerning the Brazilian Stenhelmoides fauna.