Key to the known species of the genus Helochares from Japan (all instars) 2

1. Secondary sensilla between PA6 and PA7 absent (Fig. 29A); mandible with two setae (MN1 and MN5) (Figs. 30 B–C); distal part of outer face of stipes with two setae (MX 5 and MX 6) (Figs. 30 D–E); lateral face of mentum without stout setae (Figs. 30 F–G). First instar. ............................................................................................................................... 2

- Secondary sensilla between PA6 and PA7 present (Figs. 34, 43); mandible with more than two setae (Figs. 33 C–D); distal part of outer face of stipes with three setae (Figs. 33 E–F); lateral face of mentum with stout setae (Figs. 33 G–H). Second and third instars. ......... 4

2. Epistomal lobe with one short scale-like seta and two short, trichoid to spiniform setae (Fig. 29C). ..................................................... H. (Helochares) pallens (MacLeay, 1825)

- Epistomal lobe with two short scale-like setae and two short, trichoid to spiniform setae (Fig. 36C). ....................................................................................................................... 3

3. Seta PA7 trichoid (Fig. 36A). ....................... H. (Hydrobaticus) anchoralis Sharp, 1890

- Seta PA7 scale-like (Fig. 38A). ............... H. (Hydrobaticus) nipponicus Hebauer, 1995

4. Epistomal lobe with one short scale-like seta and two short, trichoid to spiniform setae (Fig. 33A). ..................................................... H. (Helochares) pallens (MacLeay, 1825)

- Epistomal lobe with two short scale-like setae and two short, trichoid to spiniform setae (Fig. 42A). ............................................... H. (Hydrobaticus) nipponicus Hebauer, 1995