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 : 26

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