HYPHYDRINI, Sharp, 1880

Alarie, Yves, Michat, Mariano C. & Challet, Gilbert L., 2017, Larval Description and Phylogenetic Placement of the South African Endemic Genera Coelhydrus Sharp and Darwinhydrus Sharp (Coleoptera: Dytiscidae: Hydroporinae: Hyphydrini), The Coleopterists Bulletin 71 (2), pp. 389-401 : 397-398

KEY TO THE THIRD INSTARS OF HYPHYDRINI

GENERA

The following key was prepared to separate members of the Hyphydrini genera known in enough detail. However, because Hyphydrini is very speciose and the larvae of several genera are still unknown, the present key is preliminary. We propose it to provide a template upon which future descriptions can be compared.

1. Egg bursters present on frontocly- peus.................................................... Instar I

1 ′. Egg bursters absent on frontoclypeus ..... 2

2. Spiracles absent on mesothorax and abdominal segments I–VII ................. Instar II

2 ′. Spiracles present on mesothorax and abdominal segments I–VII (Instar III). ...... 3

3. Dorsal metafemoral natatory setae absent; procoxa with less than 15 secondary setae; femur with less than 8 natatory setae; tibia with less than 10 natatory setae; tarsus with less than 10 natatory setae; ratio A4/A3> 0.30; smaller species, HL less than 1.00 mm .............. 4

3 ′. Dorsal metafemoral natatory setae present; procoxa with more than 15 secondary setae; femur with more than 8 natatory setae; tibia with more than 10 natatory setae; tarsus with more than 10 natatory setae; ratio A4/A3 <0.30; larger species, HL more than 1.00 mm ......................................... 5

4. Frontoclypeus with several lateral notches well-visible in dorsal view (e.g., Fig. 5 ); siphon clearly constricted at point of insertion of urogomphus (e.g., Figs. 2 , 6 ); primary setae LA3, LA4, and LA5 articulated distally on prementum; ratio HL/LAS> 1.50; ratio MP/LP> 1.60; ratio LP2/LP1 <1.30; siphon lacking spine-like setae on ventral surface ....... Microdytes Balfour-Browne

4 ′. Frontoclypeus lacking lateral notches (e.g., Fig. 1 ); siphon not constricted at point of insertion of urogomphus; primary setae LA3, LA4, and LA5 articulated proximally on prementum; ratio HL/LAS <1.20; ratio MP/LP <1.40; ratio LP2/LP1> 1.50; siphon with at least 1 ventral spine-like setae on ventral surface ...... .... Desmopachria Babington

5. Frontoclypeus with several lateral notches well-visible in dorsal view ( Fig. 5 ); ratio MP/LP <1.90 ................................. 6

5 ′. Frontoclypeus lacking lateral notches ( Fig. 2 ); ratio MP/LP> 2.00 ....................... 7

6. Smaller species, HL <1.50 mm; ratio HL/LAS <2.20 ........ Darwinhydrus Sharp

6 ′. Larger species, HL> 1.80 mm; ratio HL/ LAS> 2.40 ................... Andex Sharp

7. Siphon elongated, not constricted at point of insertion of urogomphus; ratio HL/LAS <1.20; siphon with several spine-like setae on ventral surface; metathoracic leg <3.30 times HW ................. Hyphydrus Illiger

7 ′. Siphon short, clearly constricted at point of insertion of urogomphus ( Fig. 2 ); ratio HL/LAS> 2.40; siphon lacking spinelike setae on ventral surface; metathoracic leg> 3.50 times HW ..................... 8

8. Ratio MP/LP <2.20; ratio LAS/ HW> 1.20; larger species, HL> 1.60 mm ............. Primospes Sharp

8 ′. Ratio MP/LP> 2.40; ratio LAS/ HW <0.90; smaller species, HL <1.50 mm ............ Coelhydrus Sharp

Figures

Figs. 5–6. Darwinhydrus solidus, instar III. 5) Head capsule, dorsal view; 6) Abdominal segment VIII and proximal portion of urogomphi, dorsal view. Scale bars = 0.50 mm.

Figs. 1–2. Coelhydrus brevicollis, instar III. 1) Head capsule, dorsal view; 2) Abdominal segment VIII and proximal portion of urogomphi, dorsal view. Scale bars = 0.50 mm.