Hygrobia, Latreille, 1804

Michat, Mariano C., Alarie, Yves & Hendrich, Lars, 2014, Description of the third instar of Hygrobia nigra (Clark, 1862) (Coleoptera: Paelobiidae), with a key for the identification of mature larvae of Hygrobia Latreille, 1804 and phylogenetic analysis, Zootaxa 3827 (3), pp. 318-330 : 326

Key to the known third-instar larvae of Hygrobia

The reader is referred to Alarie et al. (2004) for figures regarding H. australasiae , H. hermanni and H. wattsi .

1. Frontoclypeolabrum broadly rounded, not distinctly produced into a nasale; ratio A3'/A4> 0.80; ratio LAS/HL> 1.90; ratio U/ LAS <0.80; meso- and metatibial natatory setae more abundant (> 135 and>130 respectively)............. .. H. hermanni

- Frontoclypeolabrum produced into a short nasale; ratio A3'/A4 <0.80; ratio LAS/HL <1.70; ratio U/LAS> 0.80; meso- and metatibial natatory setae less abundant (<125 and <105 respectively).......................................... 2

2. Meso- and metacoxa with 1 ventral secondary seta; protibia with more than 35 anteroventral secondary setae...... H. wattsi

- Meso- and metacoxa with more than 3 ventral secondary setae; protibia with less than 25 anteroventral secondary setae.... 3

3. Urogomphi longer (total length = 5.40 mm), more than 1.40 times LAS ( Fig. 17 ); coxae with a larger number of dorsal secondary setae (> 25,> 40 and> 50 respectively) ( Figs. 12–15 ); ratio A3'/A4> 0.50............................... H. nigra

- Urogomphi shorter (total length = 5.08 mm), less than 1.30 times LAS; coxae with a lesser number of dorsal secondary setae (<20, <20 and <25 respectively); ratio A3'/A4 <0.50............................................ H. australasiae

Figures

FIGURES 16–17. Hygrobia nigra, third-instar larva. 16, abdominal segments I–VII, dorsal aspect; 17, abdominal segment VIII and urogomphi, dorsal aspect. Scale bar = 0.80 mm.

FIGURES 12–15. Hygrobia nigra, third-instar larva. 12, left prothoracic leg, anterior aspect; 13, right prothoracic leg, posterior aspect; 14, left metathoracic leg, anterior aspect; 15, right metathoracic leg, posterior aspect. Numbers and lowercase letters indicate primary setae and pores respectively. Additional and secondary setae and pores not labeled. CO: coxa; FE: femur; PT: pretarsus; TA: tarsus; TI: tibia; TR: trochanter. Scale bars = 0.40 mm.