Larval morphology of the genus Hydrocassis Fairmaire (Coleoptera: Hydrophilidae)

Abstract

The larval morphology of the genus Hydrocassis Fairmaire, 1878 is described on the basis of three species of the genus: second instar of Hydrocassis jengi Satô, 1998, all instars of Hydrocassis lacustris (Sharp, 1884) and second and third instars of Hydrocassis uncinata Ji et Schödl, 1998; the former two belong to the Hydrocassis scapulata species group and the latter to the Hydrocassis scaphoides species group. Primary chaetotaxy of the larval head of Hydrocassis is described based on the first instar larvae of H. lacustris. Larval morphology of all genera of Sperchopsini with known larvae is summarized based on descriptions and figures from the literature, which are compared with Hydrocassis: larval morphology of Hydrocassis is similar to that of Sperchopsis, and the presumably closely related genus Ametor is distinguishable from Hydrocassis by characters of larval morphology. A key to the Sperchopsini genera on the basis of larval characters is provided.

Keywords:

• Coleoptera
• Hydrophilidae
• Sperchopsini
• larva
• Hydrocassis
• Hydrocassis jengi
• Hydrocassis lacustris
• Hydrocassis uncinata
• chaetotaxy

Acknowledgements

We thank Masahiro Sakai and Hiroyuki Yoshitomi (EUMJ) for giving us the opportunity to examine the museum collection of the Ehime University Museum, and Jun'ichi Fujiwara (Laboratory of Insect Science, Kobe University) for a valuable specimen of Hydrocassis jengi and information of habitat of the species. We also thank Masahiro Ôhara and Kazunori Yoshizawa (SEHU), Miguel Archangelsky (LIESA, Universidad Nacional de la Patagonia San Juan Bosco), Martin Fikáček (National Museum, Prague) and Hiroyuki Yoshitomi (EUMJ) for their kind advice and critical reading of the draft of the manuscript, and the two anonymous reviewers for their constructive criticisms. The first author thanks Hiroyuki Wakahara and his family for their kind support during the Laotian field work. This study was partly supported by Grant-in-Aid for JSPS Fellows to Y. Minoshima.