Coleoptera: Hydrophilidae) 51 (Suppl.) 2011 Yûsuke Minoshima • Masakazu Hayashi
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AACTACTA EENTOMOLOGICANTOMOLOGICA MUSEI NATIONALIS PRAGAE Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae) 51 (suppl.) 2011 Yûsuke Minoshima • Masakazu Hayashi Hydrochara affinis Acta Entomologica Musei Nationalis Pragae Volume 51 (supplementum) Date of issue: June 30, 2011 Chairman of the editorial board: Josef Jelínek (Czech Republic) Editor-in-chief: Petr Kment (Czech Republic) Associate editors: Martin Fikáček (Czech Republic) Igor Malenovský (Czech Republic) English language editor: Grey T. Gustafson (USA) Advisory board: Jitka Aldhoun (United Kingdom) Zdeněk Laštůvka (Czech Republic) Michael Balke (Germany) Lubomír Masner (Canada) Jan Bezděk (Czech Republic) Wolfram Mey (Germany) David S. Boukal (Czech Republic) Carl W. Schaefer (USA) Freddy Bravo (Brazil) Aleš Smetana (Canada) Vladimir M. Gnezdilov (Russia) Alexey Yu. Solodovnikov (Denmark) Jiří Hájek (Czech Republic) Pavel Štys (Czech Republic) Petr Kočárek (Czech Republic) Sonja Wedmann (Germany) Published biannually by the National Museum, Václavské náměstí 68, CZ-115 79 Praha 1, Czech Republic. Scope of the journal: Acta Entomologica Musei Nationalis Pragae (AEMNP) publishes entomological papers focused on taxonomy, nomenclature, morphology, bionomics and phylogeny as well as catalogues, faunistic papers dealing with large areas and short notes. Manuscripts should be sent to: AEMNP journal offi ce, Department of Entomology, National Museum, Kunratice 1, CZ-148 00 Praha 4, Czech Republic. E-mails: [email protected], [email protected]. Journal web page: http://www.nm.cz/publikace/acta.php; http://www.aemnp.eu Typeset & design: M. Fikáček. Printed by H.R.G. spol. s r.o., Svitavská 1203, Litomyšl, Czech Republic. Distributed by the Department of Entomology, National Museum, Praha. Indexed in Biological Abstracts, EBSCO, Entomology Abstracts, SCOPUS, Zoological Record and Scientifi c Citation Index Expanded. ISSN 0374-1036 (Print) © Národní muzeum, Praha – 2011 ISSN 1804-6487 (Online) ISBN 978-80-7036-296-9 This is Supplementum 13 of the Acta Entomologica Musei Nationalis Pragae. Cover: Larva of Hydrochara affi nis (Sharp, 1873) (Coleoptera: Hydrophilidae). Drawn by Yûsuke Minoshima. Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae) Yûsuke Minoshima Masakazu Hayashi ACTA ENTOMOLOGICA MUSEI NATIONALIS PRAGUE volume 51 (supplementum) National Museum, Prague 2011 ACTA ENTOMOLOGICA MUSEI NATIONALIS PRAGAE Published 30.vi.2011 Volume 51(supplementum), pp. 1–118 ISSN 0374-1036 Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae) Yûsuke MINOSHIMA1) & Masakazu HAYASHI2) 1) Systematic Entomology, Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589 Japan; e-mail: [email protected] 2) Hoshizaki Green Foundation, Okinoshima 1659-5, Sono-chô, Izumo-shi, Shimane Pref., 691-0076 Japan; e-mail: [email protected] Abstract. Larval morphology of the Japanese representatives of the tribes Acidoce- rini, Hydrobiusini and Hydrophilini (Coleoptera, Hydrophilidae, Hydrophilinae) is described. Eleven species assigned to seven genera are studied: Agraphydrus narusei (Satô, 1960) (fi rst and third instars), Enochrus (Holcophilydrus) simu- lans (Sharp, 1873) (all instars), E. (H.) umbratus Sharp, 1884 (third instar), E. (Methydrus) japonicus (Sharp, 1873) (all instars), Helochares (Helochares) pallens (MacLeay, 1825) (all instars), H. (Hydrobaticus) anchoralis Sharp, 1890 (fi rst instar), H. (Hydrobaticus) nipponicus Hebauer, 1995 (all instars), Hydrobius pauper Sharp, 1884 (second and third instars), Hydrochara affi nis (Sharp, 1873) (fi rst and third instars), Hydrophilus (Hydrophilus) acuminatus Motschulsky, 1854 (all instars), and Sternolophus (Sternolophus) rufi pes (Fabricius, 1792) (all instars). Three aspects of larval morphology were evaluated for each species studied: (1) general morphology; (2) chaetotaxy of the head capsule and its appendages; (3) morphological transformations between instars. Primary chaetotaxy is rather stable among taxa and instars examined, thus we were able to distinguish primary and secondary sensilla even in the majority of the second and third instar larvae stu- died. Secondary chaetotaxy shows slight intraspecifi c variation. Presence/absence of secondary sensilla may be useful at least for distinguishing the fi rst larval instar from later instars, and often for distinguishing all three larval instars. The arran- gement of primary and secondary sensilla shows differences among the tribes and genera studied, and between species in Enochrus Thomson, 1859 and Helochares Mulsant, 1844. The pattern of character transformations between larval instars is rather constant among taxa examined. Generic keys of aquatic Hydrophilidae, tribes Acidocerini and Hydrophilini from Japan, and key to Japanese species of Enochrus and Helochares with known larvae are provided. Key words. Coleoptera, Hydrophilidae, Hydrophilinae, Acidocerini, Hydrobiu- sini, Hydrophilini, larva, morphology, chaetotaxy, morphological transformation, taxonomy, Japan 2 MINOSHIMA & HAYASHI: Larval morphology of Japanese Hydrophilidae Contents 1. Introduction .......................................................................................................... 3 2. Material and methods ......................................................................................... 4 3. General morphology of Japanese Acidocerini, Hydrobiusini and Hydrophilini .................................................................................................. 9 4. Systematics .................................................................................................. 15 4.1. Tribe Acidocerini ........................................................................................... 15 Key to the genera of the tribe Acidocerini from Japan ............................. 16 Genus Agraphydrus Régimbart, 1903 ....................................................... 17 Agraphydrus narusei (Satô, 1960) ..................................................... 17 Genus Chasmogenus Sharp, 1882 ............................................................. 26 Genus Enochrus Thomson, 1859 .............................................................. 26 Key to the known species of the genus Enochrus from Japan ........... 30 Enochrus (Holcophilydrus) simulans (Sharp, 1873) .......................... 30 Enochrus (Holcophilydrus) umbratus Sharp, 1884 ............................ 37 Enochrus (Methydrus) japonicus (Sharp, 1873) ................................ 41 Genus Helochares Mulsant, 1844 ............................................................. 50 Key to the known species of the genus Helochares from Japan ........ 53 Helochares (Helochares) pallens (MacLeay, 1825) .......................... 53 Helochares (Hydrobaticus) anchoralis Sharp, 1890 .......................... 61 Helochares (Hydrobaticus) nipponicus Hebauer, 1995 ..................... 64 4.2. Tribe Hydrobiusini ..........................................................................................73 Genus Hydrobius Leach, 1815 .................................................................. 74 Hydrobius pauper Sharp, 1884 .......................................................... 74 4.3. Tribe Hydrophilini ......................................................................................... 81 Key to the genera of the tribe Hydrophilini from Japan ........................... 83 Genus Hydrochara Berthold, 1827 ........................................................... 83 Hydrochara affi nis (Sharp, 1873) ...................................................... 83 Genus Hydrophilus Geoffroy, 1762 .......................................................... 91 Hydrophilus (Hydrophilus) acuminatus Motschulsky, 1854 ............. 91 Genus Sternolophus Solier, 1834 .............................................................. 99 Sternolophus (Sternolophus) rufi pes (Fabricius, 1792) ..................... 99 4.4. Key to the known genera of the aquatic Hydrophilidae from Japan ........... 108 5. Conclusions ....................................................................................................... 110 5.1. Chaetotaxy of the larval head ..................................................................... 110 5.2. Morphological transformations .................................................................. 113 6. Acknowledgements ............................................................................................ 114 7. References ........................................................................................................ 115 Acta Entomologica Musei Nationalis Pragae, 51(supplementum), 2011 3 1. Introduction The water scavenger beetle tribes Acidocerini, Hydrobiusini and Hydrophilini (i.e., representatives of the former tribe Hydrophilini sensu HANSEN (1991)) represent together one of the largest groups of the family Hydrophilidae, containing about a quarter of the known species (HANSEN 1999, SHORT & HEBAUER 2006, SHORT & FIKÁČEK 2011). The representatives of these tribes occur in various aquatic habitats including artifi cial ones such as paddy fi elds and adjacent ponds. The larvae are predatory, while the adults are mainly herbivores or omnivores, thus they play different roles in freshwater ecosystems during their development. Several different phylogenetic hypotheses