Mystonectes coelamboides, (Fall, 1923)

Alarie, Yves & Michat, Mariano C., 2025, Description of the mature larvae of the halophilic diving beetles Mystonectes coelamboides (Fall, 1923) and M. panaminti (Fall, 1923) and comparison with other known Deronectina (Coleoptera: Dytiscidae, Hydroporinae), Zootaxa 5666 (2), pp. 225-238 : 233-234

Description of larvae of M. coelamboides ( Fall, 1923)

( Figs 17–21 )

Source of material. The larvae studied were collected ex societate imaginis ( Fig. 16 ) at the following locality: USA: California. Inyo Co.: Death Valley National Park , Salt Creek , ca 20 km west of Furnace Creek , off CA Route 190, 11.iv.1999, 36°35.436′N 116°59.433′W, four instar III, Y. Alarie leg. The identification is safe as M. coelamboides was the only Deronectina species collected at that location .

Diagnosis: Instar III larva of M. coelamboides can readily be distinguished from that of M. panaminti by its larger size, HL = 0.99–1.05 mm, HW = 0.77–0.85 mm, U1 = 2.20–2.35 mm ( Table 1 ), higher number of secondary setae along anteroventral margin of metafemur (> 13) and metafemur as a whole (> 43) ( Table 2 ), and broader abdomen ( Fig. 17 ).

Body ( Fig. 17 ): Measurements and ratios that characterize the body shape are shown in Table 2 .

Head ( Fig. 18 ): HL = 0.99–1.05 mm, HW = 0.77–0.85 mm, FRL = 0.74–0.83 mm, OCW = 0.52–0.61 mm; ventroapical margin of frontoclypeus with 32–33 spatulate setae [= lamellae clypeales of Bertrand (1972)].

Thorax ( Figs 17 , 20–21 ): L3 = 2.78–2.88 mm.

Abdomen (Figs, 17, 19): LAS ( Fig. 19 ) = 0.36–0.39 mm. Urogomphus. U1 = 2.20–2.35 mm, U1+ U2 = 2.71–2.84 mm, U1/U2 = 4.19–5.59.

Chaetotaxy: Lateroventral margin of PA with 7–8 secondary spine-like setae ( Fig. 18 ); secondary leg setation detailed in Table 2 and Figs 20–21 .

Ecology: Salt Creek is part of Death Valley National Park. It is a significant water feature in the park, though it is often only a seasonal creek. Adult and larval specimens of M. coelamboides ( Figs 16–17 ) were collected along the creek margin.

Distribution: So far only known from a few scattered records in southeastern California and New Mexico, USA. ( Zimmerman & Smith 1975).

Figures

FIGURES 16–17. Mystonectes coelamboides (Fall, 1923): 16. adult habitus, dorsal aspect; 17. instar III habitus, dorsal aspect (specimen preserved in 75% alcohol for 36 years). Scale bars = 1 mm.

FIGURE 18–19. Mystonectes coelamboides (Fall, 1923), instar III: 18. head capsule, dorsal aspect; 19. abdominal segment VIII, dorsal aspect; PA, parietal. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bars = 0.2 mm.

FIGURE 20–21. Mystonectes coelamboides (Fall, 1923), instar III: 20. metathoracic leg, anterior surface; 21. metathoracic leg, posterior surface. CO, coxa; FE, femur; TA, tarsus; TI, tibia; TR, trochanter. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bar = 0.2 mm.