Water Beetles as Models in Ecology and Evolution.

Beetles have colonized water many times during their history, with some of these events involving extensive evolutionary radiations and multiple transitions between land and water. With over 13,000 described species, they are one of the most diverse macroinvertebrate groups in most nonmarine aquatic habitats and occur on all continents except Antarctica. A combination of wide geographical and ecological range and relatively accessible taxonomy makes these insects an excellent model system for addressing a variety of questions in ecology and evolution. Work on water beetles has recently made important contributions to fields as diverse as DNA taxonomy, macroecology, historical biogeography, sexual selection, and conservation biology, as well as predicting organismal responses to global change. Aquatic beetles have some of the best resolved phylogenies of any comparably diverse insect group, and this, coupled with recent advances in taxonomic and ecological knowledge, is likely to drive an expansion of studies in the future.

Entomological Collections in the Age of Big Data.

With a million described species and more than half a billion preserved specimens, the large scale of insect collections is unequaled by those of any other group. Advances in genomics, collection digitization, and imaging have begun to more fully harness the power that such large data stores can provide. These new approaches and technologies have transformed how entomological collections are managed and utilized. While genomic research has fundamentally changed the way many specimens are collected and curated, advances in technology have shown promise for extracting sequence data from the vast holdings already in museums. Efforts to mainstream specimen digitization have taken root and have accelerated traditional taxonomic studies as well as distribution modeling and global change research. Emerging imaging technologies such as microcomputed tomography and confocal laser scanning microscopy are changing how morphology can be investigated. This review provides an overview of how the realization of big data has transformed our field and what may lie in store.

New species and new records of the hygropetric water beetle genus Oocyclus Sharp from South America (Coleoptera: Hydrophilidae).

Three new species of Oocyclus Sharp, 1882 are described from tropical South America: O. maluz sp. n. (Venezuela), O. miza sp. n. (Venezuela), and O. brunneus sp. n. (Bolivia). New distributional records are provided for O. andinus Short & García, O. coromoto Short & García (newly recorded from Suriname), O. floccus Short & García (newly recorded from Guyana and Suriname), O. iguazu (Oliva), O. meridensis Short & García, O. petra Short & García (newly recorded from Guyana and Suriname), O. trio Short & Kadosoe (newly recorded from Guyana), O. trujillo Short & García, and O. yubai Clarkson & Short (newly recorded from Paraguay). Updates to the keys of the Brazilian and Venezuelan Oocyclus species are provided.

Revision of the Neotropical water scavenger beetle genus Novochares Girón & Short (Coleoptera, Hydrophilidae, Acidocerinae).

The water scavenger beetle genus Novochares Girón & Short, 2021 is revised using a combination of adult morphological and DNA sequence data. Thirty-eight new species are described: Novocharesaperitosp. nov. (Bolivia), N.bacasp. nov. (Brazil, Ecuador, Peru, Suriname), N.bidenssp. nov. (Brazil), N.bisinuatussp. nov. (Brazil), N.clavierisp. nov. (Brazil, French Guiana, Peru), N.dantasp. nov. (Venezuela), N.dentatussp. nov. (Ecuador, Venezuela), N.dicranospathussp. nov. (Peru), N.duosp. nov. (Brazil, French Guiana, Guyana, Suriname, Venezuela), N.fernandezaesp. nov. (Brazil, Peru, Venezuela), N.florifersp. nov. (Brazil), N.furcatussp. nov. (Brazil), N.garciaisp. nov. (Venezuela), N.garfosp. nov. (Brazil), N.geminussp. nov. (Brazil), N.kawsaysp. nov. (Ecuador, Peru), N.latussp. nov. (Brazil), N.minorsp. nov. (Peru, Suriname, Venezuela), N.mojenossp. nov. (Bolivia), N.murasp. nov. (Brazil), N.orchissp. nov. (Brazil, French Guiana, Suriname), N.pastinumsp. nov. (Ecuador), N.pertusussp. nov. (Brazil), N.piaroasp. nov. (Venezuela), N.pilatussp. nov. (Venezuela), N.pumesp. nov. (Venezuela), N.punctatostriatussp. nov. (Brazil, French Guiana, Guyana, Peru, Suriname), N.quadrispinussp. nov. (Brazil, Guyana, Suriname), N.spanglerisp. nov. (Peru), N.tambopatensesp. nov. (Peru), N.tenedorsp. nov. (Guyana, Venezuela), N.triangularissp. nov. (Bolivia, Brazil, Paraguay), N.tridentissp. nov. (Brazil), N.trifurcatussp. nov. (Peru), N.unguissp. nov. (Bolivia, Peru), N.xingusp. nov. (Brazil), and N.yanomamisp. nov. (Venezuela), N.yorasp. nov. (Peru). One new synonym is proposed: N.carmona (Short, 2005) syn. nov. was determined to be a junior subjective synonym of N.chaquensis (Fernández, 1982). Novocharesinornatus (d'Orchymont, 1926) is considered incertae sedis. Updated distributions and new records are provided for most previously described species in the genus. Novocharessallaei (Sharp, 1882) is considered native to the USA (Florida) and not an introduced species as previously suggested. Novochares now contains 52 species and spans the entire Neotropical region from Mexico to Argentina, including the Caribbean islands.

ResumenEl género de escarabajos acuáticos detritívoros Novochares Girón & Short, 2021, se revisa usando una combinación de datos morfológicos de los adultos y secuencias de ADN. Se describen 38 especies nuevas: Novocharesaperitosp. nov. (Bolivia), N.bacasp. nov. (Brasil, Ecuador, Perú, Surinam), N.bidenssp. nov. (Brasil), N.bisinuatussp. nov. (Brasil), N.clavierisp. nov. (Brasil, Guyana Francesa, Perú), N.dantasp. nov. (Venezuela), N.dentatussp. nov. (Ecuador, Venezuela), N.dicranospathussp. nov. (Perú), N.duosp. nov. (Brasil, Guyana, Guyana Francesa, Surinam, Venezuela), N.fernandezaesp. nov. (Brasil, Perú, Venezuela), N.florifersp. nov. (Brasil), N.furcatussp. nov. (Brasil), N.garciaisp. nov. (Venezuela), N.garfosp. nov. (Brasil), N.geminussp. nov. (Brasil), N.kawsaysp. nov. (Ecuador, Perú), N.latussp. nov. (Brasil), N.minorsp. nov. (Perú, Surinam, Venezuela), N.mojenossp. nov. (Bolivia), N.murasp. nov. (Brasil), N.orchissp. nov. (Brasil, Guyana Francesa, Surinam), N.pastinumsp. nov. (Ecuador), N.pertusussp. nov. (Brasil), N.piaroasp. nov. (Venezuela), N.pilatussp. nov. (Venezuela), N.pumesp. nov. (Venezuela), N.punctatostriatussp. nov. (Brasil, Guyana, Guyana Francesa, Perú, Surinam), N.quadrispinussp. nov. (Brasil, Guyana, Surinam), N.spanglerisp. nov. (Perú), N.tambopatensesp. nov. (Perú), N.tenedorsp. nov. (Guyana, Venezuela), N.triangularissp. nov. (Bolivia, Brasil, Paraguay), N.tridentissp. nov. (Brasil), N.trifurcatussp. nov. (Perú), N.unguissp. nov. (Bolivia, Perú), N.xingusp. nov. (Brasil), and N.yanomamisp. nov. (Venezuela), N.yorasp. nov. (Perú). Se propone una nueva sinonimia: N.carmona (Short, 2005) syn. nov. se determinó como sinónimo subjetivo posterior de N.chaquensis (Fernández, 1982). Novocharesinornatus (d'Orchymont, 1926) se considera incertae sedis. Se proveen distribuciones actualizadas y nuevos registros para la mayoría de las especies descritas previamente en el género. Novocharessallaei (Sharp, 1882) es considerada nativa en los Estados Unidos de América (Florida) y no como una especie potencialmente introducida como se afirmaba previamente. Novochares ahora contiene 52 especies y se extiende a lo largo de toda la región neotropical, desde México hasta Argentina, incluyendo las islas del Caribe.

New species and new distributional records of the hygropetric water scavenger beetle genus Oocyclus Sharp (Coleoptera: Hydrophilidae) from the Guiana Shield.

The species of the water scavenger beetle genus Oocyclus Sharp are reviewed for the Guiana Shield region of South America. Seven species are recorded, including one here described as new: Oocyclus paraiso sp. n. from the Brazilian state of Pará. New records of previously described species are also reported for Brazil, French Guiana, Guyana, and Suriname. The aedeagus of O. coromoto Short & García is illustrated for the first time. As with all other known members of the genus, all Guiana Shield species are hygropetric habitat specialists. A key to the Oocyclus of the Guiana Shield is provided.

Revision of the water scavenger beetle genus Notionotus Spangler, 1972 in the Neotropical Region (Coleoptera, Hydrophilidae, Enochrinae).

The Neotropical species of the water scavenger beetle genus Notionotus Spangler, 1972 are revised using an integrative taxonomic approach combining morphology with DNA sequence data from two genes. Support exists for four putative species groups into which 18 species are placed, including twelve that are described here as new: N.bicolor sp. nov. (Suriname), N.bifidus sp. nov. (Venezuela), N.brunbadius sp. nov. (Brazil), N.garciae sp. nov. (Brazil), N.giraldoi sp. nov. (Brazil), N.insignitus sp. nov. (Venezuela), N.juma sp. nov. (Brazil), N.parvus sp. nov. (Suriname), N.patamona sp. nov. (Guyana), N.peruensis sp. nov. (Peru), N.retusus sp. nov. (Guyana), and N.vatius sp. nov. (Brazil). Four new synonymies are created: N.shorti Queney syn. nov. is found to be conspecific with N.dilucidus Queney; N.edibethae García syn. nov., N.nucleus Perkins syn. nov., and N.perijanus García syn. nov. are found to be conspecific with N.tricarinatus Perkins. New records are provided for all previously described species except N.mexicanus Perkins. Within the Neotropical region, the range of the genus is greatly expanded and now known from as far south as Bolivia and the Brazilian state of Mato Grosso do Sul. While a few species are found in hygropetric habitats, most are associated with the margins of forested streams. Genitalia and habitus images are provided for nearly all species, as well as a key to the four species groups.

ResumenLas especies de escarabajos acuáticos detritívoros neotropicales del género Notionotus Spangler, 1972 son revisadas usando taxonomía integrativa, combinando morfología con datos de secuencias de ADN para dos genes. Se encontró soporte para cuatro grupos de especies conformados por 18 especies, incluyendo 12 que son aquí descritas como nuevas: N.bicolor sp. nov. (Suriname), N.bifidus sp. nov. (Venezuela), N.brunbadius sp. nov. (Brazil), N.garciae sp. nov. (Brazil), N.giraldoi sp. nov. (Brazil), N.insignitus sp. nov. (Venezuela), N.juma sp. nov. (Brazil), N.parvus sp. nov. (Suriname), N.patamona sp. nov. (Guyana), N.peruensis sp. nov. (Peru), N.retusus sp. nov. (Guyana), N.vatius sp. nov. (Brazil). Se sinonimizan cuatro especies: N.shorti Queney syn. nov. se considera conespecífico con N.dilucidus Queney; N.edibethae García syn. nov., N.nucleus Perkins syn. nov., y N.perijanus García syn. nov. son conespecíficos con N.tricarinatus Perkins. Nuevos registros son provistos para todas las especies previamente descritas excepto para N.mexicanus Perkins. Hasta el momento, en la región neotropical, el rango de distribución del género es ampliamente expandido, se conoce desde el Sur de Bolivia hasta el estado brasileño de Mato Grosso do Sul. Si bien algunas especies son encontradas en hábitats higropétricos, la mayoría de ellas están asociadas a las orillas de arroyos boscosos. Se proveen imágenes del hábito dorsal y genitalia para la mayoría de las especies, al igual que la clave para los cuatro grupos de especies.

New species and new distributional records of the hygropetric water scavenger beetle genus Oocyclus Sharp (Coleoptera, Hydrophilidae) from the Brazilian Shield.

Nine new species of the water scavenger beetle genus Oocyclus Sharp, 1882 are described from the Brazilian Shield: O. ecolab sp. n., O. espinhacu sp. n., O. giganteus sp. n., O. humboldti sp. n., O. lacia sp. n., O. ovalis sp. n., O. sulcatus sp. n., O. thrixdiastematus sp. n., and O. thysanus sp. n. New locality records are provided for four species previously known from Brazil: O. rotundus Clarkson Short, 2012, O. pilosus Jordo, Clarkon Ferreira-Jr, 2018, O. xanthus Clarkson Short, 2012 and O. yubai Clarkson Short, 2012. All species are associated with rock-face seepages such as wet rocks, waterfalls, and seepages. An updated key to the Brazilian species of Oocyclus is provided.

Review of the New World Notomicrus Sharp (Coleoptera, Noteridae) I: Circumscription of species groups and review of the josiahi group with description of a new species from Brazil.

The New World species of the minute aquatic beetle genus Notomicrus Sharp compose a much greater diversity than their Old World congeners, with 14 of the 17 known Notomicrus species occurring in the Neotropics. A recent phylogenetic study recovered four primary New World species groups and found that there are a number of undescribed species across all of these main lineages. Here, we provide a taxonomic key to these New World species groups, including two described species that we currently do not place in any group ("incertae sedis" species), complete with images and illustrations of diagnostic characters and taxonomic notes including a list of known species in each group. This work provides a scaffold for further planned taxonomic revisions within the genus. In addition, we review the first of the four New World groups, the josiahi species group and describe one new taxon, N. interstinctus sp. nov. from northern Brazil. Provided are descriptions, habitus images and illustrations of diagnostic characters.

The Acidocerinae (Coleoptera, Hydrophilidae): taxonomy, classification, and catalog of species.

The cosmopolitan subfamily Acidocerinae (Coleoptera: Hydrophilidae) is one of the largest and most taxonomically challenging lineages of water scavenger beetles. Recent phylogenetic studies have substantially advanced our understanding of acidocerine relationships but also illuminated the twin challenges of poorly delineated generic concepts and a classification broadly incompatible with the phylogeny. Here, these two challenges are addressed by providing a comprehensive synthesis and taxonomic tools for the Acidocerinae, including (1) a brief history and the current state of acidocerine classification, (2) a review of acidocerine ecology and collection methods, (3) the current knowledge of larval and fossil acidocerines, (4) a morphological primer on characters of taxonomic and systematic importance within the lineage, (5) a key to the world genera of Acidocerinae, (6) diagnoses, habitus, and aedeagal images, distribution maps, and summary of knowledge for each of the 23 extant genera in the subfamily, and (7) a complete annotated taxonomic catalog including the published distributions, synonyms, and references for all described 541 acidocerine species recognized as of 1 April 2021. The following nomenclatural acts are proposed to bring the phylogeny and classification into alignment: Colossochares gen. nov. is established to accommodate two African species previously described as Helochares (s. str.); Novochares gen. nov. is newly established to accommodate 15 Neotropical species previously included in Helochares (s. str.); the remaining Helochares subgenera Helocharimorphus Kuwert syn. nov. and Hydrobaticus MacLeay syn. nov. are synonymized with Helochares Mulsant. Peltochares Régimbart sensu nov. is redefined to include eight Old World species previously included in Helochares (s. str.). A lectotype is designated for Peltochares conspicuus Régimbart, the type species of the genus. The taxonomic and morphological circumscription of Helochares sensu nov. is narrowed and redefined.

ResumenLa subfamilia Acidocerinae (Coleoptera: Hydrophilidae) es cosmopolita y representa uno de los linajes más diversos y taxonómicamente más desafiantes de escarabajos acuáticos detritívoros. Estudios filogenéticos recientes han incrementado considerablemente nuestro entendimiento sobre las relaciones entre acidocerinos, así como iluminaron los conceptos genéricos pobremente definidos y una clasificación ampliamente incompatible con la filogenia. Aquí se abordan estos dos desafíos proporcionando una síntesis integral y herramientas taxonómicas para Acidocerinae, incluyendo (1) un resumen de la historia y estado actual de la clasificación de Acidocerinae, (2) una revisión de la ecología y los métodos de recolección para acidocerinos, (3) el conocimiento actual de acidocerinos larvales y fósiles, (4) un manual morfológico básico sobre caracteres de importancia taxonómica y sistemática dentro del linaje, (5) una clave para los géneros de Acidocerinae del mundo, (6) diagnosis, imágenes del hábito y del edeago, mapas de distribución y resumen del conocimiento actual para cada uno de los 23 géneros existentes en la subfamilia, y (7) un catálogo taxonómico anotado y completo que incluye las distribuciones publicadas, sinónimos y referencias para todas las 541 especies de Acidocerinae descritas y reconocidas al 1 de abril de 2021. Se proponen los siguientes actos taxonómicos para alinear la clasificación con la filogenia: Colossochares gen. nov. se establece para incluir dos especies africanas descritas previamente como Helochares (s. str.); Novochares gen. nov. se establece como nuevo para acomodar 15 especies neotropicales previamente incluidas en Helochares (s. str.); los subgéneros restantes de Helochares Mulsant, Helocharimorphus Kuwert syn. nov. e Hydrobaticus MacLeay syn. nov. se sinonimizan con Helochares. Peltochares Régimbart sensu nov. es redefinido para incluir ocho especies del viejo mundo previamente incluidas en Helochares (s. str.). Se designa un lectotipo para Peltochares conspicuus Régimbart, la especie tipo del género. La circunscripción taxonómica y morfológica de Helochares sensu nov. se reduce y redefine.

New species and records of Chasmogenus Sharp, 1882 from the southwestern margin of the Guiana Shield (Coleoptera: Hydrophilidae: Acidocerinae).

The Neotropical water scavenger beetle genus Chasmogenus Sharp, 1882 is a diverse lineage with 34 described species. Here, three new species from the southwestern margin of the Guiana Shield are described using an integrative approach combining adult morphology and molecular data: Chasmogenus clinatus sp. n. (Brazil: Amazonas, Venezuela: Amazonas), C. gironae sp. n. (Venezuela: Amazonas), and C. inpa sp. n. (Brazil: Amazonas). Examination of the male genitalia is essential for confident identifications and thus unassociated females may prove extremely difficult to identify. New distributional records in Brazil for C. acuminatus Smith Short, 2020 are provided as well as habitus images of newly described species and an updated key to the species from Venezuela, Suriname, Guyana, French Guiana and northern Brazil.

Review of the Neotropical water scavenger beetle genus Tobochares Short & García, 2007 (Coleoptera, Hydrophilidae, Acidocerinae): new lineages, new species, and new records.

The water scavenger beetle genus Tobochares Short & García, 2007 currently contains ten species, including one known but formally undescribed taxon. Although Tobochares was revised in 2017, ongoing fieldwork as well as an expanded concept of the genus has led to the recognition of numerous additional species. Here a combination of morphological and molecular data is presented to review this newly found Tobochares diversity. Fifteen new species are described from South America, bringing the total number of known species to 25: Tobochares akoerio sp. nov. (Suriname), T. arawak sp. nov. (Guyana), T. anthonyae sp. nov. (Venezuela: Bolívar), T. atures sp. nov., (Venezuela: Amazonas), T. benettii sp. nov. (Brazil: Amazonas), T. canaima sp. nov. (Venezuela: Bolívar), T. communis sp. nov. (Brazil: Amapá and Roraima, Guyana, Suriname, Venezuela: Bolívar), T. fusus sp. nov. (Brazil: Amapá, French Guiana), T. goias sp. nov. (Brazil: Goiás), T. kappel sp. nov. (Suriname), T. kolokoe sp. nov. (Suriname), T. luteomargo sp. nov. (Venezuela: Bolívar), T. microps sp. nov. (Suriname), T. pemon sp. nov. (Venezuela: Bolívar), and T. romanoae sp. nov. (Brazil: Roraima). Both morphological and molecular analyses support four clades within the genus, which are here diagnosed and described as species groups. New distributional records are provided for T. kusad Kohlenberg & Short, 2017 and T. sipaliwini Short & Kadosoe, 2011, both of which are recorded from Brazil for the first time. Previously restricted to the Guiana Shield region of South America, the distributional range of the genus is now broadly expanded to include localities as far south as the central Brazilian state of Goiás. Consistent with the biology of the previously described species, almost all the new species described here are associated with seepage and wet rock habitats. Remarkably, one species, T. fusus sp. nov., was collected in both seepage habitats as well as in the rotting fruits of Clusia Linnaeus (Clusiaceae), making it one of the few known acidocerines with terrestrial habits outside of the genus Quadriops Hansen, 1999. High-resolution images of most species are included, as well as a key to species groups, species, and habitat photographs.

ResumenEl género de escarabajos acuáticos detritívoros Tobochares Short & García, 2007 actualmente contiene 10 especies, incluyendo un taxón conocido, pero no descrito. Aunque el género fue revisado en 2017, trabajo de campo en curso, así como un concepto ampliado del género han llevado al reconocimiento de numerosas especies adicionales. Aquí presentamos una combinación de datos morfológicos y moleculares para revisar esta diversidad de Tobochares recientemente encontrada. Quince especies nuevas son descritas de Suramérica, elevando el número total de especies conocidas a 25: Tobochares akoerio sp. nov. (Surinam), T. arawak sp. nov. (Guyana), T. anthonyae sp. nov. (Venezuela: Bolívar), T. atures sp. nov., (Venezuela: Amazonas), T. benettii sp. nov. (Brasil: Amazonas), T. canaima sp. nov. (Venezuela: Bolívar), T. communis sp. nov. (Brasil: Amapá y Roraima, Guyana, Surinam, Venezuela: Bolívar), T. fusus sp. nov. (Brasil: Amapá, Guyana Francesa), T. goias sp. nov. (Brasil: Goiás), T. kappel sp. nov. (Surinam), T. kolokoe sp. nov. (Surinam), T. luteomargo sp. nov. (Venezuela: Bolívar), T. microps sp. nov. (Surinam), T. pemon sp. nov. (Venezuela: Bolívar), y T. romanoae sp. nov. (Brasil: Roraima). También encontramos soporte morfológico y molecular para cuatro clados dentro del género, los cuales son aquí diagnosticados y descritos como grupos de especies. Nuevos registros de distribución son provistos para T. kusad Kohlenberg & Short, 2017 y T. sipaliwini Short & Kadosoe, 2011, ambos registrados para Brasil por primera vez. Previamente restringido a la región del Escudo Guyanés de Suramérica, el rango de distribución del género es ahora ampliamente expandido para incluir localidades tan al sur como el estado de Goiás en el centro de Brasil. Consistentes con la biología de las especies previamente conocidas, casi todas las especies descritas aquí están asociadas con hábitats higropétricos o áreas de drenaje sobre rocas. Notablemente, una especie, T. fusus sp. nov., fue colectada tanto en hábitats higropétricos como en frutos en descomposición de Clusia Linneo (Clusiaceae), constituyéndose en uno de los pocos acidocerinos conocidos con hábitos terrestres fuera del género Quadriops Hansen, 1999. Se incluyen imágenes de alta resolución de la mayoría de las especies incluidas, una clave para los grupos de especies y las especies, así como fotografías de los hábitats.

Review of the genus Chasmogenus Sharp, 1882 of northeastern South America with an emphasis on Venezuela, Suriname, and Guyana (Coleoptera, Hydrophilidae, Acidocerinae).

The water scavenger beetle genus Chasmogenus Sharp, 1882 is reviewed in northeastern South America using an integrative approach that combines adult morphology and molecular data from the gene cytochrome c oxidase I (COI). Eighteen new species are described: Chasmogenus acuminatus sp. nov. (Brazil, French Guiana, Guyana, Suriname), C. amplius sp. nov. (Venezuela), C. berbicensis sp. nov. (Guyana), C. brownsbergensis sp. nov. (Suriname), C. castaneus sp. nov. (Venezuela), C. clavijoi sp. nov. (Venezuela), C. cuspifer sp. nov. (Venezuela), C. flavomarginatus sp. nov. (Venezuela), C. gato sp. nov. (Venezuela), C. guianensis sp. nov. (Suriname, Guyana), C. ignotus sp. nov. (Brazil), C. ligulatus sp. nov. (Suriname), C. lineatus sp. nov. (Venezuela), C. pandus sp. nov. (Brazil, French Guiana, Suriname), C. schmits sp. nov. (Suriname), C. sinnamarensis sp. nov. (French Guiana), C. tafelbergensis sp. nov. (Suriname), and C. undulatus sp. nov. (Guyana). We found genetic support for an additional new species in Guyana which is currently only known from females that we refer to as Chasmogenus sp. C. We examined the holotypes of the four species previously known from the region, and found that C. occidentalis García syn. nov. and C. yukparum García syn. nov. are conspecific with C. bariorum García, 2000 and are synonymized with that species, which is here redescribed. We redescribe C. australis García and expand the range of this species to include northern Brazil, Guyana, and French Guiana. All species are aquatic, with most being associated with forested streams and forest pools. Of the 21 species, more than half (11) are only known from a single locality indicating the genus may have many more micro-endemic species yet to be discovered in the region. Characters of the male genitalia are essential for confirming the identity of some species, consequently it is not always possible to make positive identifications of unassociated female specimens based on morphology alone. Habitus images are provided as well as a revised key to the genus for northeastern South America.

Hydaticus aequalis sp. n. and a new record of H. devexus Trémouilles, 1996 from Brazil (Coleoptera, Dytiscidae, Hydaticini).

Hydaticus aequalis sp. n. is described from Brazil, where it was recently discovered in the central lowlands region of the Amazon forest. The new species differs from all other Neotropical congeners by its uniformly brown dorsal surface and the shape of medial lobe. The dorsal habitus and male genitalia are illustrated, and a distribution map is provided. The habitat, a small stream and associated forest pool, is illustrated and described. In addition, a new record of H. devexus Trémouilles, 1996, previously known from a single specimen, is reported from the highlands of northeastern Brazil, and a modified key to Neotropical species of the genus is provided.

Rediscovery of the Neotropical water scavenger beetle Protistolophus spangleri Short with notes on its habitat and behavior (Coleoptera: Hydrophilidae: Hydrophilinae).

The water scavenger beetle genus Protistolophus Short contains a single species, P. spangleri Short, 2010, known from southern Venezuela. The genus was hitherto known only from a single partly-incomplete male specimen, making it one of the rarest and most poorly known aquatic hydrophilid genera in the world. Only one other New World aquatic hydrophilid genus, the Ecuadorian cave endemic Troglochares Spangler, is known from a single specimen or locality. In a phylogenetic analysis of the Hydrophilini based on adult morphology, the genus Protistolophus was resolved as the sister taxon to the remaining genera of the tribe, implying it is an ancient and possibly relict lineage-it possesses a very unusual combination of characters, including a very weakly developed mesoventral keel. It was the only genus not included in a recent molecular phylogeny of the Hydrophilini as no suitable material was available for DNA (Toussaint et al. 2017).

Three additional new genera of acidocerine water scavenger beetles from the Guiana and Brazilian Shield regions of South America (Coleoptera, Hydrophilidae, Acidocerinae).

Recent study of the water scavenger beetle subfamily Acidocerinae in the Neotropical region has uncovered numerous undescribed species that are not able to be placed in existing genera. Here, we describe three new genera to accommodate 17 of these new species from South America: Aulonochares gen. nov. for Aulonochareslingulatus sp. nov. (French Guiana, Suriname), Aulonocharesnovoairensis sp. nov. (Brazil), and Aulonocharestubulus sp. nov. (Brazil, Guyana, Suriname, Venezuela); Ephydrolithus gen. nov. for Ephydrolithushamadae sp. nov. (Brazil), Ephydrolithusminor sp. nov. (Brazil), Ephydrolithusogmos sp. nov. (Brazil), Ephydrolithusspiculatus sp. nov. (Brazil), and Ephydrolithusteli sp. nov. (Brazil); and Primocerus gen. nov. for Primoceruscuspidis sp. nov. (Venezuela), Primocerusgigas sp. nov. (Venezuela), Primocerusneutrum sp. nov. (Guyana, Suriname, Venezuela), Primocerusocellatus sp. nov. (Venezuela), Primoceruspetilus sp. nov. (Brazil), Primoceruspijiguaense sp. nov. (Venezuela), Primocerusmaipure sp. nov. (Venezuela), Primocerussemipubescens sp. nov. (Guyana), and Primocerusstriatolatus sp. nov. (Suriname). The genus Ephydrolithus gen. nov. is currently known to be restricted to seepages in the mountainous regions of the Brazilian Shield. Aulonochares gen. nov. and Primocerus gen. nov. are both currently only known from the Guiana Shield, though widespread in that region where they are associated with streams and seeps. We present differential diagnoses, maps, habitat details, and illustrations of all new genera and species here described.

ResumenEl estudio reciente de escarabajos acuáticos de la subfamilia Acidocerinae en la región neotropical, ha revelado numerosas especies no descritas que no pueden ser atribuidas a los géneros existentes. Aquí describimos tres géneros nuevos para acomodar 17 de estas especies nuevas de Suramérica: Aulonochares gen. nov. para Aulonochareslingulatus sp. nov. (Guyana Francesa, Surinam), Aulonocharesnovoairensis sp. nov. (Brasil), y Aulonocharestubulus sp. nov. (Brasil, Guyana, Surinam, Venezuela); Ephydrolithus gen. nov. para Ephydrolithushamadae sp. nov. (Brasil), Ephydrolithusminor sp. nov. (Brasil), Ephydrolithusogmos sp. nov. (Brasil), Ephydrolithusspiculatus sp. nov. (Brasil), y Ephydrolithusteli sp. nov. (Brasil); y Primocerus gen. nov. para Primoceruscuspidis sp. nov. (Venezuela), Primocerusgigas sp. nov. (Venezuela), Primocerusneutrum sp. nov. (Guyana, Surinam, Venezuela), Primocerusocellatus sp. nov. (Venezuela), Primoceruspetilus sp. nov. (Brazil), Primoceruspijiguaense sp. nov. (Venezuela), Primocerusmaipure sp. nov. (Venezuela), Primocerussemipubescens sp. nov. (Guyana), y Primocerusstriatolatus sp. nov. (Surinam). El género Ephydrolithus gen. nov. se restringe hasta ahora a hábitats higropétricos en las regiones montañosas del Escudo Brasileño. Aulonochares gen. nov. y Primocerus gen. nov. son ambos hasta ahora conocidos del Escudo Guyanés, no obstante, ampliamente distribuidos en esa región en la que están asociados con corrientes y hábitats higropétricos. Presentamos diagnosis diferenciales, mapas, detalles sobre los hábitats e ilustraciones para todos los géneros y especies que aquí se describen.

Three new genera of acidocerine water scavenger beetles from tropical South America (Coleoptera, Hydrophilidae, Acidocerinae).

Recent collecting efforts in the Neotropics have led to the discovery of numerous new species and lineages of aquatic beetles. Here, three new genera are described to accommodate fifteen new species of water scavenger beetles of the subfamily Acidocerinae from northern South America: Crucisternumgen. n. for C. escalerasp. n. (Venezuela), C. ouboterisp. n. (Guyana, French Guiana, Suriname, Venezuela), C. queneyisp. n. (French Guiana), C. sinuatussp. n. (Brazil), C. toboganensissp. n. (Venezuela), C. vanessaesp. n. (Suriname), and C. xingusp. n. (Brazil); Katasophistesgen. n. for K. charynaesp. n. (Peru), K. cuzcosp. n. (Peru), K. meridasp. n. (Venezuela) and K. superficialissp. n. (Ecuador); and Nanosaphesgen. n. for N. castaneussp. n. (Brazil), N. hesperussp. n. (Suriname), N. punctatussp. n. (Guyana), and N. tricolorsp. n. (Guyana, Suriname). It was also found that the monotypic Neotropical endemic genus Dieroxenus Spangler, 1979, syn. n. is congeneric with Chasmogenus Sharp, 1882 resulting in the single new combination Chasmogenus cremnobates (Spangler, 1979), comb. n.. Katasophistes meridasp. n. is known exclusively from seepage habitats, while the remaining taxa described herein are primarily associated with the margins of densely forested streams. Diagnoses, illustrations, distribution maps, and habitat summaries are provided for all new genera and species. A key to the genera of Acidocerinae of the New World is provided.

ResumenRecientes esfuerzos de colecta en el neotrópico han llevado al descubrimiento de numerosas especies y linajes nuevos de escarabajos acuáticos. Aquí se describen tres géneros nuevos, para acomodar quince especies nuevas de escarabajos acuáticos de la subfamilia Acidocerinae, del norte de Suramérica: Crucisternumgen. n. para C. escalerasp. n. (Venezuela), C. ouboterisp. n. (Guyana, Guyana Francesa, Surinam, Venezuela), C. queneyisp. n. (Guyana Francesa), C. sinuatussp. n. (Brasil), C. toboganensissp. n. (Venezuela), C. vanessaesp. n. (Surinam), y C. xingusp. n. (Brasil); Katasophistesgen. n. para K. charynaesp. n. (Perú), K. cuzcosp. n. (Perú), K. meridasp. n. (Venezuela) y K. superficialissp. n. (Ecuador); y Nanosaphesgen. n. para N. castaneussp. n. (Brazil), N. hesperussp. n. (Surinam), N. punctatussp. n. (Guyana), y N. tricolorsp. n. (Guyana, Surinam). También se encontró que el género Dieroxenus Spangler, 1979, syn. n., el cual es monotípico, neotropical y endémico, es congenérico con Chasmogenus Sharp, 1882, lo que resulta en la nueva combinación Chasmogenus cremnobates (Spangler, 1979), comb. n.. Katasophistes meridasp. n. se conoce exclusivamente de hábitats higropétricos, mientras que los taxa restantes que se describen aquí, están primordialmente asociados con los márgenes de corrientes densamente forestadas. Diagnosis, ilustraciones, mapas de distribución y un resumen de los hábitats, son provistos para todos los géneros y especies nuevas. Se provee además una clave para la identificación de géneros de Acidocerinae del nuevo mundo.

Review of the Helochares (Hydrobaticus) MacLeay of the New World (Coleoptera: Hydrophilidae: Acidocerinae).

New World species assigned to the Helochares subgenus Hydrobaticus MacLeay are reviewed based on adult morphology and DNA sequence data. Nine species are recognized, including five here described as new: Helochares (Hydrobaticus) laevis n. sp. (Mexico), H. (Hydrobaticus) nexus n. sp. (Ecuador, Panama, Venezuela), H. (Hydrobaticus) politus n. sp. (Guatemala), H. (Hydrobaticus) trujillo n. sp. (Venezuela), and H. (Hydrobaticus) zamora n. sp. (Ecuador). New records are provided for the three previously described species: Helochares (Hydrobaticus) championi Sharp, 1882 (Costa Rica, Guatemala, Nicaragua), H. (Hydrobaticus) maculicollis Mulsant, 1844 (United States), and H. (Hydrobaticus) normatus (LeConte, 1861) (United States to Costa Rica). A ninth species, known only from five poorly preserved female specimens from Peru, is left undescribed until additional material can be found. Most species are known to exhibit some parental care, with the egg case being attached to the abdomen of and carried by the female. Intraspecific genetic distances within several species are very high, in some cases more than 8% in the mitochondrial gene COI, suggesting there may be additional cryptic species remaining to be identified. All taxa are illustrated and a key to species is provided.

Notomicrus petrareptans sp. n., a new seep-dwelling species of Noteridae from Suriname (Coleoptera: Adephaga).

Notomicrus petrareptans sp. n. is described from an inselberg seepage in southwestern Suriname. This species is diagnosable by a combination of its weakly punctate elytra, respective shapes of the pro- and mesotarsal claws (males), and long and slender median lobe of the aedeagus. This is the first member of the subfamily Notomicrinae to be described from hygropetric seep habitats and only the second known seep-dwelling species of the family Noteridae. Diagnostic characters are illustrated and habitat images are provided.

Revision of the Neotropical water scavenger beetle genus Tobochares Short & García, 2007 (Coleoptera, Hydrophilidae, Acidocerinae).

The genus Tobochares Short & García, 2007 is revised. A combination of morphological and molecular data provide support for ten distinct species. Five new species are described: T. canaliculatussp. n. (Venezuela), T. canthussp. n. (Venezuela), T. emarginatussp. n. (Suriname), T. kusadsp. n. (Guyana), and T. pallidussp. n. (Venezuela). All four preexisting species are redescribed. A tenth species, known from a single female from Venezuela, is left undescribed pending the collection of additional specimens. New collecting records are provided for T. sulcatus Short & García, 2007 and T. kasikasima Short, 2013. Tobochares sipaliwini Short & Kadosoe, 2011 is newly recorded from Guyana. All species are associated with seepage or wet rock habitats, although some species have also been found along the margins of streams that flow over rocky substrates. High-resolution images including scanning electron micrographs are provided, as well as a key to species and habitat photographs.

Revision of the Neotropical water scavenger beetle genus Quadriops Hansen, 1999 (Coleoptera, Hydrophilidae, Acidocerinae).

The genus Quadriops Hansen, 1999 is revised and redescribed. The genus is found to contain six species, including two that are here described as new: Quadriops clusiasp. n. (Brazil, Guyana, Suriname) and Q. acroreiussp. n. (Suriname, French Guiana). Two species are found to be junior subjective synonyms of Q. depressus Hansen, 1999: Q. amazonensis García, 2000, syn. n. and Q. politus Hansen, 1999, syn. n. The male of Q. similaris Hansen, 1999 is described for the first time. New records are provided for Q. dentatus Hansen, 1999, Q. reticulatus Hansen, 1999, and Q. similaris. All species are described and illustrated in detail. Most species are confirmed as having a terrestrial way of life, with several species being found in rotten fruits, sap flows, and dead wood. Furthermore, we discuss ecological trends of the species given their collecting information.

ResumenEl género Quadriops Hansen, 1999 es revisado y redescrito. El género contiene seis especies, incluyendo dos que se describen aquí como nuevas: Quadriops clusiasp. n. (Brasil, Guyana, Surinam) y Q. acroreiussp. n. (Surinam, Guyana Francesa). Dos especies se sinonimizan con Q. depressus Hansen, 1999: Q. amazonensis García, 2000, syn. n. y Q. politus Hansen, 1999, syn. n. El macho de Q. similaris Hansen, 1999 se describe por primera vez. Se proveen nuevos registros para Q. dentatus Hansen, 1999, Q. reticulatus Hansen, 1999, y Q. similaris. Todas las especies son descritas e ilustradas en detalle. La mayoría de las especies presentan un modo de vida terrestre, con varias especies encontradas en frutos podridos, flujos de savia y madera muerta. Además, se discuten tendencias ecológicas de las especies dada su información de colecta.