Enochrus, Thomson, 1859

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 : 30

Key to the known species of the genus Enochrus from Japan (all instars) 1

1. Secondary sensilla between PA6 and PA7 absent ( Fig. 13A ); mandible with two setae (MN1 and MN5) ( Figs. 14 B–C); distal part of outer face of stipes with two setae ( MX 5 and MX 6) ( Figs. 14 D–E); lateral face of mentum without stout setae ( Figs. 14 F–G). First instar. ............................................................................................................................... 3

– Secondary sensilla between PA6 and PA7 present ( Fig. 18 ); mandible with more than two setae ( Figs. 17 C–D); distal part of outer face of stipes with three setae ( Figs. 17 E–F); lateral face of mentum with stout setae ( Figs. 17 G–H). ............................................................. 2

2. Lateral face of mentum with two stout setae ( Figs. 15 H–I). Second instar. ................... 4

– Lateral face of mentum with more than three setae (usually four to five) ( Figs. 17 G–H). Third instar. ..................................................................................................................... 5

3 Prolegs with stout spines, the spines strongly curbed to apex ( Figs. 28 A–D). .................. ..................................................................... E. (Holcophilydrus) simulans ( Sharp, 1873)

– Prolegs with slender spines, the spines not strongly curved to apex ( Figs. 28 E–G). ......... ........................................................................... E. (Methydrus) japonicus ( Sharp, 1873)

4. Inner face of stipes with more than six stout setae ( Figs. 24 E–F); prolegs with slender spines ( Fig. 28F ). .............................................. E. (Methydrus) japonicus ( Sharp, 1873)

– Inner face of stipes with five stout setae ( Figs. 15 F–G); prolegs with stout spines ( Fig. 28B ). .......................................................... E. (Holcophilydrus) simulans ( Sharp, 1873)

5. Inner face of stipes with more than six stout setae ( Figs. 26 E–F); prolegs with slender spines ( Fig. 28G ). ............................................. E. (Methydrus) japonicus ( Sharp, 1873)

– Inner face of stipes with five stout setae ( Figs. 17 E–F); prolegs with stout spines ( Figs. 28 C–D). .............................................................................................................................. ............ E. (Holcophilydrus) simulans ( Sharp, 1873) and E. (H.) umbratus Sharp, 1884

Figures

Fig. 13. Head capsule of Enochrus (Holcophilydrus) simulans (Sharp, 1873), first instar.A – dorsal view; B – ventral view; C – detail of anterior margin of head capsule, dorsal view.

Fig. 14. Head appendages of Enochrus (Holcophilydrus) simulans (Sharp, 1873), 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. 18. Enochrus (Holcophilydrus) simulans (Sharp, 1873), chaetotaxy of head capsule, dorsal view.A–C – second instar larva. A – median part of head capsule; B–C – intraspecific variation of secondary sensilla between PA6 and PA7. D–F – third instar larva. D – median part of head capsule; E–F – intraspecific variation of secondary sensilla between PA6 and PA7. Secondary sensilla are marked by a black rhombus.

Fig. 17. Enochrus (Holcophilydrus) simulans (Sharp, 1873), third instar.A – clypeolabrum, dorsal view; B – antenna, dorsal view; C–D – mandibles, dorsal view; E – maxilla, dorsal view; F – maxilla, ventral view; G – labium, dorsal view; H – labium, ventral view.

Fig.15. Enochrus (Holcophilydrus) simulans (Sharp, 1873), second instar.A – clypeolabrum,dorsal view; B – antenna, dorsal view; C – antenna, detail of outer membranous area on pedicel, ventral view; D–E – mandibles, dorsal view; F – maxilla, dorsal view; G – maxilla, ventral view; H – labium, dorsal view; I – labium, ventral view.

Fig. 28. Prolegs of Enochrus Thomson, 1859 speci- es, ventral view. A–C – Enochrus (Holcophilydrus) simulans (Sharp, 1873): A – first instar; B – second instar; C – third instar. D – Enochrus (Holcophilydrus) umbratus Sharp, 1884, third instar. E–G – Enochrus (Methydrus) japonicus (Sharp, 1873): E – first instar; F – second instar; G – third instar.Photographs were taken with compound light microscope.

Fig. 24. Enochrus (Methydrus) japonicus (Sharp, 1873), second instar.A – clypeolabrum, dorsal view; B – antenna, dorsal view; C–D – mandibles, dorsal view; E – maxilla, dorsal view; F – maxilla, ventral view; G – labium, dorsal view; H – labium, ventral view.

Fig. 26. Enochrus (Methydrus) japonicus (Sharp, 1873), third instar. A – clypeolabrum, dorsal view; B – antenna, dorsal view; C–D – mandibles, dorsal view; E – maxilla, dorsal view; F – maxilla, ventral view; G – labium, dorsal view; H – labium, ventral view.