Mystonectes panaminti, (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 : 229

Description of instar III larva of M. panaminti ( Fall, 1923)

( Figs 3–15 )

Source of material. The larvae studied were collected ex societate imaginis ( Fig. 2 ) at the following locality: USA: California. Inyo Co.: Death Valley National Park , Badwater Basin , off Badwater Road , ca. 27 km south of California Route 190 , 11.iv.1999, 36°13.801′N 116°46.064′W, 15 instar III, Y.Alarie leg. The identification was safe as M. panaminti is the only dytiscid collected at that location .

Diagnosis: Instar III larva of M. panaminti can readily be distinguished from that of M. coelamboides by its smaller size, HL = 0.88–0.95 mm, HW = 0.65–0.71 mm, U1 = 1.98–2.20 mm ( Table 1 ), lesser number of secondary setae along anteroventral margin of metafemur (<12) and metafemur as a whole (<42) ( Table 2 ), and narrower abdomen ( Fig. 3 ).

Body ( Fig. 3 ): Measurements and ratios that characterize the body shape are shown in Table 1 .

Head ( Figs 4–13 ): HL = 0.88–0.95 mm, HW = 0.65–0.71 mm, FRL = 0.67–0.72 mm, OCW = 0.43–0.48 mm; ventroapical margin of frontoclypeus with 31–35 spatulate setae [= lamellae clypeales of Bertrand (1972)].

Thorax ( Figs 3 , 14–15 ): L3 = 2.47–2.68 mm.

Abdomen ( Figs 3 , 5–6 ): LAS ( Fig. 5 ) = 0.32–0.33 mm. Urogomphus ( Fig. 6 ). U1 = 1.98–2.20 mm, U1+ U2 = 2.20–2.50 mm, U1/U2 = 5.79–7.27.

Chaetotaxy: Lateroventral margin of PA with 6–8 secondary spine-like setae ( Fig. 4 ); secondary leg setation detailed in Table 2 and Figs 14–15 .

Ecology: Adult and larval specimens of M. panaminti ( Figs 2–3 ) were collected from water slowly flowing below salt crust.

Distribution: So far only known from Death Valley National Park, California, USA ( Zimmerman & Smith 1975).

Figures

FIGURES 2–3. Mystonectes panaminti (Fall, 1923): 2. adult habitus, dorsal aspect; 3. instar III habitus, dorsal aspect (specimen preserved in 75% alcohol for 36 years). Scale bars = 1 mm.

FIGURES 4–6. Mystonectes panaminti (Fall, 1923), instar III: 4. head capsule, dorsal aspect; 5. abdominal segment VIII, dorsal aspect; 6. urogomphus, dorsal aspect; PA, parietal. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bars = 0.2 mm.

FIGURES 7–13. Mystonectes panaminti (Fall, 1923), instar III: 7. antenna, dorsal aspect; 8. antenna, ventral aspect; 9. mandible, dorsal aspect; 10. maxilla, dorsal aspect; 11. maxilla, ventral aspect; 12. labium, dorsal aspect; 13. labium, ventral aspect; A3’, lateral process of antennomere 3; AN, antenna; gAN, antennal group; LA, labium: gLA, labial group; MN, mandible: MX, maxilla; gMX, maxillary group; sp, spinula. Numbers and lowercase letters refer to primary setae and pores, respectively: *, secondary seta. Scale bars = 0.1 mm.

FIGURES 14–15. Mystonectes panaminti (Fall, 1923), instar III: 14. metathoracic leg, anterior surface; 15. 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.