Hydrophilus Geoffroy, 1762

Minoshima, Yûsuke & Hayashi, Masakazu, 2011, Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae (suppl.) 51, pp. 1-118 : 91

Genus Hydrophilus Geoffroy, 1762

( Figs. 2C , 56–59 , 64C , 66D )

Diagnosis. Larvae of this genus are easily distinguishable from other Japanese genera of the Hydrophilini by their large body size; additional diagnostic characters are: (1) frontal lines U-shaped, forming a straight line in posterior part of the head ( Fig. 58A ); (2) nasale smooth ( Fig. 56C ); (3) epistomal lobes almost symmetrical, rounded ( Fig. 56C ); (4) mandibles asymmetrical, right mandible with two inner teeth, left mandible with one inner tooth ( Figs. 57 B–C); (5) abdominal segments with short setiferous projections on each side.

Figures

Fig. 2. Habitus of the larvae of Hydrophilini, dorsal view. A–B – Hydrochara affinis (Sharp, 1873): A – first instar; B – third instar. C – Hydrophilus acuminatus Motschulsky, 1854, third instar. D–E – Sternolophus (Sternolophus) rufipes (Fabricius, 1792): D – second instar; E – third instar.

Fig. 56. Head capsule of Hydrophilus acuminatus Motschulsky, 1854, first instar.A – dorsal view; B – ventral view; C – detail of anterior margin of head capsule, dorsal view.

Fig. 57. Head appendages of Hydrophilus acuminatus Motschulsky, 1854, first instar. A – antenna, dorsal view; B–C – mandibles, dorsal view; D – maxilla, dorsal view; E – maxilla, ventral view; F – labium, dorsal view; G – labium, ventral view.

Fig. 58. Hydrophilus acuminatus Motschulsky, 1854, third instar. A – head, dorsal view; B – spiracular atrium, dorsal view.

Fig. 59. Head appendages of Hydrophilus acuminatus Motschulsky, 1854, third instar. A – antenna, dorsal view; B – antenna, ventral view; C – detail of inner surface of intersegmental membrane between pedicel and flagellum; D – maxilla, dorsal view; E – maxilla, ventral view.

Fig. 64. Prosternum and mesothoracic legs of Hydrophilini species.A – prosternum of Hydrochara affinis (Sharp, 1873), third instar, ventral view. B–D – mesothoracic legs, first instar, anterior view: B – Hydrochara affinis (Sharp, 1873); C – Hydrophilus acuminatus Motschulsky, 1854; D – Sternolophus rufipes (Fabricius, 1792).

Fig. 66. Examples of morphological transformations between instars in the maxilla of the Acidocerini and Hydrophilini larvae. A–B – dorsal view, C – ventral view, D – dorsal (left side) and ventral (right side) views. A – Enochrus (Holcophilydrus) simulans (Sharp, 1873), B – Enochrus (Methydrus) japonicus (Sharp, 1873), C – E. simulans, D – Hydrophilus (Hydrophilus) acuminatus Motschulsky, 1854.