Descriptions of larvae of Megadytes (Coleoptera: Dytiscidae: Dytiscinae): The hypothesis of monophyletic origin revisited

The three larval instars of Megadytes (Paramegadytes) glaucus (Brullé, 1838) and the third-instar larvae of M. (Bifurcitus) magnus Trémouilles & Bachmann, 1980 and M. (Trifurcitus) robustus (Aubé, 1838) are described and illustrated for the first time, with particular emphasis on the morphometry and chaetotaxy. A key to the subgenera of Megadytes Sharp, 1882 is presented. In a cladistic analysis of third-instar larval characters, Megadytes is resolved as non-monophyletic; the species of Cybistrini studied, except those included in the subgenus Trifurcitus Brinck, 1945, share three synapomorphies: (i) medial projection of frontoclypeus truncate apically, with many apical setae directed forwards; (ii) lateral projections of frontoclypeus project forwards, not flattened; and (iii) median process of prementum rounded apically. The clade composed of the subgenera Megadytes s. str., Paramegadytes Trémouilles & Bachmann, 1980 and Bifurcitus Brinck, 1945 along with Cybister lateralimarginalis (De Geer, 1774) is well supported by three synapomorphies: (i) head capsule subrectangular and (ii) distal third of mandible more strongly projected inwards, (iii) with a ring of long, hair-like setae. The two species of the subgenus Paramegadytes have bilobed lateral projections on the frontoclypeus. Megadytes (M.) marginithorax (Perty, 1830) is characterized by the very narrow notches between the medial and lateral projections of frontoclypeus. No synapomorphies were discovered to group together the two species of the subgenus Bifurcitus.Fil: Michat, Mariano Cruz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio de Entomologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Descriptions of larvae of Megadytes (Coleoptera: Dytiscidae: Dytiscinae): The subgenera Trifurcitus and Megadytes s. str., ground plan of chaetotaxy of the genus and phylogenetic analysis

The three larval instars of Megadytes (M.) carcharias Griffini and M. (Trifurcitus) fallax (Aubé) are described and illustrated in detail for the first time, with an emphasis on morphometry and chaetotaxy of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi. The ground plan of chaetotaxy of the genus Megadytes Sharp is described and illustrated based on three of the four recognised subgenera. First-instar larvae of Megadytes are characterised by the presence of a large number of additional sensilla on almost every part of the body. Primary chaetotaxy of the subgenera (Bifurcitus Brinck based on third instar) is very similar, with few differences including (1) shape of the setae on the anterior margin of the frontoclypeus; (2) presence or absence of a ring of multi-branched setae on distal third of mandible; and (3) number of setae on the urogomphus. A cladistic analysis of Dytiscidae, based on 169 larval characters and 34 taxa, indicates that: (1) Trifurcitus Brinck deserves generic status; (2) Cybistrini are not closely related to Hydroporinae; (3) the absence of a galea in Cybistrini is a secondary loss independent of that in Hydroporinae; (4) Cybistrini are well supported by many characters (including several aspects of first-instar chaetotaxy).Fil: Michat, Mariano Cruz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio de Entomologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Larval description and chaetotaxic analysis of dineutus sinuosipennis laporte, 1840, with a key for the identification of larvae of the tribe Dineutini (Coleoptera, Gyrinidae)

The larvae of the Malagasy whirligig beetle Dineutus sinuosipennis Laporte, 1840, identified using DNA sequence data, are described and illustrated for the first time, including detailed morphometric and chaetotaxic analyses of selected structures and a description of larval habitat. Larvae of the genus Dineutus Macleay, 1825 are diagnosed, and a key to identify the genera of the tribe Dineutini is presented. Larvae of Dineutus exhibit the characters traditionally recognized as autapomorphies of the Gyrinidae: body less sclerotized, egg bursters located on the parietal, one additional sensorial plate on the third antennomere, cardo and lacinia well developed, prementum completely divided, abdominal tracheal gills, and four terminal hooks on the pygopod. They also share with larvae of the other Dineutini genera these putative synapomorphies: numerous minute pore-like additional structures on the ultimate maxillary and labial palpomeres, coxal primary seta CO12 inserted submedially, and trochanteral primary seta TR2 absent. Larvae of Dineutus can be distinguished from those of other known genera of Dineutini by the posterior margin of the lacinia not dentate, tracheal gills plumose, parietal seta PA5 inserted relatively far from setae PA7–9, mandibular pores MNb and MNc inserted relatively far from each other, and tarsal seta TA1 inserted submedially.Fil: Michat, Mariano Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Gustafson, Grey T.. University of Kansas; Estados UnidosFil: Bergsten, Johannes. Swedish Museum Of Natural History; Sueci

The Juan Fernández diving beetle, Anisomeria Bistriata (Brullé 1835): habitats, communities and conservation

El archipiélago de Juan Fernández se sitúa en el océano Pacífico, aproximadamente a 600 km de la costa de Chile. Se ha sugerido que de no revertirse la degradación ambiental, la biota de estas islas pronto se verá severamente amenazada. Solamente se conocen tres especies de escarabajos buceadores (Dytiscidae) en Juan Fernández: Anisomeria bistriata (Brullé, 1835), la especie más notable dada su morfología particular, Rhantus signatus kuscheli Guignot, 1952, ambas endémicas de la isla Robinson Crusoe, y Lancetes backstromi Zimmermann, 1924, endémica de la isla Alejandro Selkirk. Con el fin de estudiar la abundancia y los hábitats de A. bistriata y R. s. kuscheli, hemos visitado la isla Robinson Crusoe. Los muestreos comprendieron pequeños esteros y algunos contenedores artificiales. Anisomeria bistriata fue recolectada en Bahía Cumberland y Plazoleta El Yunque, a altitudes de 80- 235 msnm, principalmente en contenedores artificiales, lo que posiblemente indique cierta afinidad por los hábitats lénticos. Hacia fines del verano, aproximadamente 95% de las larvas estaban en el tercer estadio, lo que podría indicar una marcada estacionalidad en el ciclo de vida de esta especie. Rhantus signatus kuscheli fue recolectado en Bahía Cumberland y Puerto Francés, a altitudes de 34-99 msnm. Contrariamente a A. bistriata, fue más frecuente en los esteros. Las larvas (la mayoría de primer estadio) fueron capturadas en el mismo estero que los adultos, en los sectores más vegetados. A pesar de la considerable degradación ambiental que ha sufrido la isla Robinson Crusoe, ambas especies no parecen severamente amenazadas.The Juan Fernández archipelago is situated in the Pacifi c Ocean, about 600 km of the coast of Chile. It has been suggested that if environmental degradation is not reversed, the biota of these islands will soon be severely threatened. Only three species of diving beetles (Dytiscidae) are known from Juan Fernández: Anisomeria bistriata (Brullé, 1835), the most remarkable species given its particular morphology, Rhantus signatus kuscheli Guignot, 1952, both endemic to Robinson Crusoe island, and Lancetes backstromi Zimmermann, 1924, endemic to Alejandro Selkirk island. In order to study the abundance and habitats of A. bistriata and R. s. kuscheli, we visited Robinson Crusoe Island. The samplings involved small creeks and some artifi cial containers. Anisomeria bistriata was collected in Bahía Cumberland and Plazoleta El Yunque, at altitudes 80-235 m asl, mainly in artifi cial containers, maybe refl ecting certain affi nity for lentic habitats. By late summer, about 95% of the larvae were third instars, which would argue in favour of a marked seasonality in the life cycle of the species. Rhantus signatus kuscheli was collected in Bahía Cumberland and Puerto Francés, at altitudes 34-99 m asl. Contrary to A. bistriata, it was more frequent in creeks. The larvae (most of them fi rst instars) were captured in the same creek as the adults, in the most vegetated portions. Despite the signifi cant environmental degradation than Robinson Crusoe island has supported, both species do not seem severely threatened.Fil: Michat, Mariano Cruz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio de Entomologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Balke, Michael. Ludwig Maximilians Universitat; Alemania. Zoologische Staatssammlung München; Alemani

Phylogenetic relationships and larval morphology of the recently described diving beetle genus Laccomimus (Coleoptera: Dytiscidae: Laccophilinae)

The larvae of the diving beetle genus Laccomimus Toledo & Michat, 2015 (Laccophilinae) are studied for the first time, based on detailed descriptions and illustrations of all instars of L. distinctus Toledo & Michat, 2015, with particular emphasis on morphometry and chaetotaxy. The phylogenetic relationships of this genus within the tribe Laccophilini are analyzed cladistically. Laccomimus is recovered as part of a clade that includes the genera Australphilus Watts, 1978, Neptosternus Sharp, 1882 and Laccophilus Leach, 1815 and is characterized by the presence of natatory setae on the tibia and tarsus, and within this clade it is a sister to the other genera. Third-instar larvae of Laccomimus and Africophilus Guignot, 1948 share the mediodistal insertion of the seta CO7 on the meso- and metacoxa, a short and spine-like seta TI6 on the metatibia, a ventrally sclerotized abdominal segment V and a short urogomphus. These characters are considered plesiomorphic and indicate a basal position of both genera within the Laccophilini. All instars of Laccomimus are characterized by the anterolateral lobes of the frontoclypeus clearly projecting beyond the anterior margin and the last abdominal segment strongly elongated. Diagnostic features of the first instar are: frontoclypeus unmodified posteriorly, lamellae clypeales thin and hair-like, pores ANe, MXb–d–f–i, LAb–c and seta TR3 absent, seta LA3 and an additional dorsal pore present on the prementum, abdominal tergites I–VII with anterior transverse carina, and ventral surface of the abdominal segment VI sclerotized.Fil: Michat, Mariano Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Toledo, Mario. Università di Parma; Itali

The larvae of Amarodytes duponti (Aubé) (Coleoptera: Dytiscidae: Hydroporinae), with comments on Bidessini larval morphology and chaetotaxy

Larval morphology of the Neotropical endemic dytiscid genus Amarodytes Régimbart is investigated. All three larval instars of A. duponti (Aubé) are described and illustrated with particular emphasis on morphometry and chaetotaxy. Larvae of A. duponti share with those of other Bidessini studied in detail the absence of the primary pore ABc. Contrary to other first instar Bidessini, A. duponti characterizes by the presence of an occipital suture and the absence of pores PAj and PAk. Amarodytes duponti is related to Allodessus bistrigatus (Clark) by the presence of secondary setae on the first urogomphomere, a unique feature among the Bidessini.Fil: Michat, Mariano Cruz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio de Entomologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alarie, Yves. Laurentian University; Canad

Description of the Second and Third Instars of Laccornellus lugubris (Aubé) (Coleoptera: Dytiscidae: Hydroporinae)

The second and third instars of Laccornellus lugubris (Aubé) are described and illustrated for the first time, including detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. Laccornellus Roughley and Wolfe shares with Canthyporus Zimmermann a similar shape and secondary setation of the last abdominal segment, the absence of secondary spine-like setae on the lateral margins of the parietal, and the presence of well-developed spinular pectens on the ventral surface of the femora (this last character also is shared with Laccornis Gozis). On the other hand, larvae of Laccornellus differ from those of Canthyporus, Laccornis, and Hydrovatus Motschulsky in the presence of secondary pores on the ventral surface of the prementum and of secondary setae on the tibia, metatarsus, and anterodorsal surface of femur. The known distributional range of L. lugubris is considerably expanded.Fil: Michat, Mariano Cruz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio de Entomologia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria; ArgentinaFil: Archangelsky, Miguel. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones en Ecología y Sistemática Animal; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria; Argentin

The last instar larva and pupa of Ora depressa (Coleoptera: Scirtidae), a marsh beetle with underwater pupation

In this contribution we describe and illustrate for the first time, detailed morphology and chaetotaxy of the last instar larva and the pupa of Ora depressa (Fabricius, 1801), and provide diagnostic characters and information on its biology. The last instar larva of O. depressa exhibits the characters traditionally recognized as diagnostic of the genus, i.e. the tip of the mandible obtuse, and the fourth maxillary palpomere long, almost as long as third palpomere. Ora depressa is characterized by a broadly elliptical body, which is widest at the metanotum, being brownish testaceous in color with several brown spots, having the dorsal surface mostly covered with numerous grooved scale-like setae and also several ungrooved scale-like setae, hair-like setae, club-like setae and pore-like sensilla distributed in a specific pattern, and the femur and tibiotarsus bearing a row of natatorial setae. The last instar larva of Ora depressa can be distinguished from those of the other known species of the genus by lobes of clypeolabrum being as long as wide and socket bristles with 2–6 inner teeth. The pupa of O. depressa differs from those of the other known species of the genus in the absence of pronotal horns and by the place where pupation occurs. Ora depressa pupates underwater, hanging from water’s surface with the aid of the laterally expanded pronotum which bears hydrophobic setation along the lateral margins.Fil: Libonatti, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Jorge, Gabrielle. Ministério da Ciência, Tecnologia, Inovações. Instituto Nacional de Pesquisas da Amazônia; BrasilFil: Archangelsky, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones en Ecología y Sistemática Animal; ArgentinaFil: Michat, Mariano Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

Larval description and phylogenetic placement of the Australian endemic genus Barretthydrus Lea, 1927 (Coleoptera: Dytiscidae: Hydroporinae: Hydroporini: Sternopriscina)

The larvae of the Australian endemic species Barretthydrus tibialis Lea, 1927 and Barretthydrus geminatus Lea, 1927 are described and illustrated for the first time, with detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. A parsimony analysis based on 118 informative larval characteristics of 34 species in all 10 tribes of the subfamily Hydroporinae was conducted using the program TNT. No clear larval morphological synapomorphies support the monophyletic origin of the tribe Hydroporini. Compared to other known larvae of Hydroporini, Barretthydrus Lea is postulated to share a closer phylogenetic relationship with Antiporus Sharp, which reinforces their inclusion in the subtribe Sternopriscina.Fil: Alarie, Yves. Laurentian University. Department of Biology; CanadáFil: Michat, Mariano Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Entomología; ArgentinaFil: Hendrich, L.. Zoologische Staatssammlung Munchen; AlemaniaFil: Watts, Chris H. S.. South Australian Museum; Australi

Morfología y quetotaxia de larvas neotropicales de Haliplus (Coleoptera: Haliplidae)

Larvae of 2 Neotropical species of Haliplus Latreille, 1802 (H. indistinctus Zimmermann, 1928 and H. subseriatus Zimmermann, 1921) are described and illustrated including detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, and legs. Except for the legs, this is the first treatment of larval primary chaetotaxy for the family Haliplidae. The larvae studied herein have 10 abdominal segments, with segment X forking into 2 caudal projections, 1 pretarsal claw, a clasping device on prothoracic legs, and numerous short tracheal gills on the body, characteristics typically found in haliplid larvae. Regarding primary chaetotaxy, they are characterized by the absence of several setae and pores which are commonly present among other families of Hydradephaga, namely seta FR6 on the frontoclypeus, seta PA16 on the parietal, setae AN2 and AN3 and pore ANg on the antenna, setae MX13 and MX14 on the maxilla, and seta CO6 on the coxa. Mandibular seta MN2 is also strongly developed as compared to other hydradephagans. The larvae of the 2 described species can be separated by comparing the distance from the base of segment X to the point at which it forks into caudal projections.Se describen e ilustran las larvas de 2 especies neotropicales de Haliplus Latreille, 1802 (H. indistinctus Zimmermann, 1928 y H. subseriatus Zimmermann, 1921), incluyendo análisis detallados de la morfometría y quetotaxia de la cápsula cefálica, apéndices cefálicos y patas. Excepto por las patas, este es el primer tratamiento de la quetotaxia primaria larval para la familia Haliplidae. Las larvas estudiadas presentan 10 segmentos abdominales, con el segmento X biburcado en 2 proyecciones caudales, 1 única uña pretarsal, 1 dispositivo de agarre en las patas protorácicas, y numerosas branquias traqueales cortas en el cuerpo, todas características típicamente encontradas en larvas de halíplidos. Con respecto a la quetotaxia primaria, están caracterizadas por la ausencia de varias setas y poros que están comúnmente presentes en otras familias de Hydradephaga, como la seta FR6 en el frontoclípeo, la seta PA16 en el parietal, las setas AN2 y AN3 y el poro ANg en la antena, las setas MX13 y MX14 en la maxila, y la seta CO6 en la coxa. Además, la seta mandibular MN2 está fuertemente desarrollada en comparación con la de otros hidradéfagos. Las larvas de las 2 especies descritas pueden separarse comparando la distancia desde la base del segmento X hasta el punto en el cual éste se bifurca en las proyecciones caudales.Fil: Michat, Mariano Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Entomología; ArgentinaFil: Archangelsky, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología. Laboratorio de Investigaciones en Ecología y Sistemática Animal; ArgentinaFil: Alarie, Yves. Laurentian University; Canad