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Male genitalia morphology in Myrmeleontidae has traditionally been insufficiently studied, although it has received increased attention for its diagnostic value in recent times. A neutral terminology has generally been applied in standard taxonomic practice, yet knowledge of an equivalent and stable terminology across taxa based on comparative morphology has been missing. Herein a detailed comparative morphology study with examples from most tribes within Myrmeleontidae, including owlflies (Ascalaphinae), attempts to relate external and internal genital structures based on a proposed groundplan for Neuroptera and Myrmeleontidae. We contend that a groundplan based on 10 abdominal segments, plus vestigial structures from an 11th segment, coherently depicts structural components across myrmeleontid taxa. A gonarcus, an element of Neuropterida amply referred in Neuroptera, is supported to represent the pair of abdominal appendages of segment X medially fused, with gonocoxite and gonostylus components. In most myrmeleontid taxa, basal (gonocoxites) and distal (gonostyli) components separate, with gonostyli positioned posteriorly with respect to gonocoxites, still united with translucent, lightly sclerotized tissue, forming a more or less conical structure, a proposed synapomorphy for the family. Ninth gonostyli are generally reduced (pulvini) and have migrated close to the base of gonarcus (10th gonocoxites). A pelta, also a potential synapomorphy for Myrmeleontidae, derives from paired setose surfaces of the 10th gonostyli, medially positioned (still evident in Bubopsis). Three structural types of gonarcus are diagnosed for illustrative purposes, as they may represent convergent constructs.

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A new species, Dilophochila glabrasp. nov. is described from the Sierra Norte, Oaxaca, Mexico. Diagnosis and im-ages (dorsal, lateral and ventral habitus, and genitalia) of the taxonomic characters are provided. Affinities with their clos-est congeners and the general distribution pattern of the genus are discussed, considering that it presents a typical Mountain Paleoamerican sub-pattern. The modifications in the mouthparts of this genus due to the specialization in the intake of pine needles are commented, as well as in two other different taxa within Anomalini.(AU)

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Resumen Introducción: La diversidad de una comunidad biológica es el resultado de procesos ecológicos e históricos, los cuales, analizados en conjunto, producen una mejor comprensión de las causas que la generan. Objetivo: Actualizamos y analizamos la diversidad específica y taxonómica de la ictiofauna del río Amacuzac, México. Métodos: Durante cinco temporadas de muestreo (2019-2020), recolectamos peces de diez sitios en el río y aplicamos un análisis de conglomerados a las variables del hábitat. Resultados: Recolectamos 7 638 individuos, siete de especies nativas y nueve no nativas, incluyendo Copadichromis borleyi, un nuevo registro para el Amacuzac. La riqueza por sitio osciló entre ocho y 13 especies. Las variables del hábitat definieron cuatro grupos. Las especies más abundantes fueron: Poeciliopsis gracilis, Poecilia maylandi y Amatitlania nigrofasciata. Las especies menos abundantes fueron: Pterygoplichtys pardalis, Ilyodon whitei, Copadichromis borleyi e Ictalurus punctatus. Las especies más relevantes fueron: A. nigrofasciata, Amphilophus istlanus, Andinoacara rivulatus, Notropis boucardi, Oreochormis sp., P. maylandi, P. gracilis y Thorichthys maculipinis. Las especies más restringidas fueron: Atherinella balsana, C. borleyi e I. punctatus. Conclusiones: Las especies en peligro de extinción, A. istlanus y N. boucardi, aun prevalecen en el río. Además, se muestra un aumento en el número de especies no nativas. Analizar la diversidad desde dos perspectivas, aporta una visión más completa de los cambios que se dan en el Río Amacuzac como consecuencia del establecimiento de especies, información que es importante para futuras estrategias de conservación.

Abstract Introduction: The diversity of a biological community is the result of ecological and historical processes, which, when analyzed jointly, produce a better understanding of the causes that generate it. Objective: We update and analyze the specific and taxonomic diversity of the ichthyofauna of the Amacuzac River, Mexico. Methods: During five sampling seasons (2019-2020) we collected fishes from ten sites in the river and applied a cluster analysis to habitat variables. Results: We collected 7 638 individuals; seven were native species and nine were non-native, including Copadichromis borleyi, a new record for the Amacuzac. Richness per site ranged from eight to 13 species. Habitat variables defined four groups. The most abundant species were Poeciliopsis gracilis, Poecilia maylandi and Amatitlania nigrofasciata. The least abundant species were: Pterygoplichtys pardalis, Ilyodon whitei, Copadichromis borleyi and Ictalurus punctatus. The most prevalent species were: A. nigrofasciata, Amphilophus istlanus, Andinoacara rivulatus, Notropis boucardi, Oreochormis sp., P. maylandi, P., gracilis and Thorichthys maculipinis. The most restricted species were: Atherinella balsana, C. borleyi and I. punctatus. Conclusions: Endangered species such as A. istlanus and N. boucardi are still prevalent in the river, but non-native species continue to increase. Analyzing the diversity from two perspectives provides a more complete view of the changes taking place in the Amacuzac River as a consequence of species establishment, information that is important for future conservation strategies.

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Results of an aquatic beetle survey at Volcán Tacaná, Mexico, are presented with five altitudinal levels in a monthly sampling regime, aiming to estimate both diversity and altitudinal distribution patterns of the aquatic beetle fauna. The first list of aquatic beetle species from this mountain is presented, comprising 40 species in 32 genera and nine families, with four species recorded for the first time from Mexico and six recorded for the first time from Chiapas. The aquatic beetle fauna is characterized by Elmidae with 20 species, Dytiscidae with eleven species, Dryopidae with three, and Epimetopidae, Hydraenidae, Hydrophilidae, Gyrinidae, Lutrochidae, and Noteridae with one species each. The species composition through the sampled altitudinal gradient (670-1,776 m) was not homogeneous, with the elmid genera Macrelmis, Heterelmis, Microcylloepus, and Austrolimnius present at all levels, while Hexanchorus, Neoelmis, and Onychelmis were present at levels 1-3 (673-1,214 m); dytiscids were mostly present at levels 4 and 5 (1,619-1,776 m), and dryopids were present only at levels 1-3. A Parsimony Analysis of Endemicity supports a general partition between altitudinal levels 1-3 and levels 4 + 5.

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The morphological limits of the genus Parabyrsopolis Ohaus (Coleoptera: Scarabaeidae: Rutelinae: Rutelini: Areodina) are redefined and Parabyrsopolis moroni new species is described from west-central Mexico. With this addition, the genus now includes five species that are distributed from southwestern United States of America to central Mexico. Diagnostic morphological characters and comparison with other Parabyrsopolis species are included, and some considerations about the morphological limits between Parabyrsopolis and Viridimicus Jameson are discussed.

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Neoscelis hexakrotes new species (Coleoptera: Scarabaeidae: Cetoniinae: Goliathini) is described from Guerrero, Mexico. Keys to identify male and female Neoscelis Schoch species and new distribution records for Neoscelis dohrni (Westwood) are provided.

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Chrysina chimalapensis new species (Coleoptera: Scarabaeidae: Rutelinae: Rutelini), from the region of Chimalapas, Oaxaca, Mexico is described and illustrated. A key to the species of the C. quiche species group is included. Plusiotis neotenochca Morón Nogueira is placed as a new junior synonym of Chrysina paulseni Hawks, and C. aenigmatica (Morón) as a new junior synonym of C. modesta Sturm. Chrysina benesi from Guatemala, and C. quetzalcoatli from Nicaragua are recorded as new country records. Chrysina quetzalcoatli Morón and C. triumphalis Morón are also recorded for the first time for the state of Oaxaca, Mexico, and C. victorina (Hope) for the state of Veracruz, Mexico.

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The origin and function of exaggerated traits exhibited by a great number of species with sexual dimorphism remain largely unexplored. The usual model considered as the evolutionary mechanism for the development of these structures is sexual selection. The nature of growth of the postocular flange (POF) in three species of the dobsonfly genus Platyneuromus (Megaloptera, Corydalidae, Corydalinae) is analyzed to explore sexual size dimorphism and allometric scaling. Results involve positive allometry of POF in males of two species, and negative allometry in males of one species, in general with a female-biased sexual dimorphism. We suggest an ancestral condition of dual incipient ornamentation in Platyneuromus, with a subsequent departure of size and shape of POF in males, triggered by sexual selection. Different sexual selection intensities may explain the parallel or divergent growth of POF within the scheme of dual ornamentation. Empirical behavioral data as well as a phylogenetic framework are necessary to clarify possible causes of phenotypic development, time of origin, and evolution of the POF.

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ABSTRACT Third stage larvae and pupae are described based on specimens collected in Mexico: Oaxaca (Cerro Zempoaltepetl), and Chiapas (Amatenango), respectively. Pupal characters are described for the first time for American Hopliinae. Habitus images and figures of diagnostic characters as well as comments on the differences between these larvae and those of Hoplia callipyge LeConte, 1856 and H. equina LeConte, 1880, the only Hopliinae larvae previously known in New World, are also included.

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Two new species of the genera Epectinaspis Blanchard and Strigoderma Burmeister from Central America, E. costaricensis new species and S. ngabe new species, are described and illustrated. For each species and their closest congeners, their diagnostic characters are discussed and the taxonomic keys for their determination are modified.

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Giesbertiolus curoei, new species is described from a female specimen collected in northwestern Panama. This species is compared with the three known species of Giesbertiolus Howden and with the genus Dialithus Parry. The genera Dialithus and Giesbertiolus are redefined to include this new species, and new diagnostic characters are provided for both. Illustrations of diagnostic characters and an identification key for the species of Giesbertiolus are provided.

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Callistethus tlapanecus, a new species collected in pine forest located at 2160 meters of altitude in eastern mountains of the state of Guerrero, Mexico is described. The morphological characters that distinguish it from other Mexican and Central American species are discussed. The diagnostic characters are illustrated, and a key to Mexican species of Callistethus is also included.

Se describe Callistethus tlapanecus, nueva especie colectada en bosques de pino situados a 2160 metros de altitud en las montañas orientales del estado de Guerrero, México. Se comentan los caracteres morfológicos que distinguen a esta especie de otras especies mexicanas y centroamericanas de Callistethus. Se ilustran los caracteres diagnósticos y se incluye una clave para separar las especies mexicanas de Callistethus.