Sandracottus femoralis Heller, 1934

Alarie, Yves, Michat, Mariano C., Shaverdo, Helena & Hájek, Jiří, 2023, Morphology of the larvae of Sandracottus femoralis Heller, 1934, and S. mixtus (Blanchard, 1843) and phylogenetic comparison with other known Aciliini (Coleoptera: Dytiscidae, Dytiscinae), Zootaxa 5263 (3), pp. 301-334 : 305

Sandracottus femoralis Heller, 1934

( Figs 1–30 )

Source of material. The three instar I, four instar II and three instar III larvae studied were associated with adults collected at the following locality: Solomon Islands, Guadalcanal: ca. 3.5 km SE of Barana village (drying up stream in shaded gorge); 09˚29.8’S, 159˚59.5’E, leg J. Hájek. The identification is safe as S. femoralis was the only Sandracottus species found in that region.

Diagnosis. Larvae of S. femoralis can be distinguished from those of S. mixtus , the only other Sandracottus species described in detail, by the following combination of characters: antennomere 1 shorter than antennomere 3 (instar I) ( Figs 3–4 ; Table 1 ); antennomeres 1–2 densely covered with spinulae ( Figs 3–4 ); anterior process of prementum shorter relative to length of labial palpomere 1 ( Tables 1 , 3 , 5); pro- and mesofemur with less than 24 and 29 anteroventral additional natatory setae, respectively (instar I) ( Table 2 ).

Figures

FIGURES 1–2. Sandracottus femoralis Heller, 1934, head capsule, instar I: (1) dorsal aspect; (2) ventral aspect. EB, egg bursters; FR, frontoclypeus; LC, lamellae clypeales; PA, parietal; TP, tentorial pits. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bar = 0.5 mm.

FIGURES 3–5. Sandracottus femoralis Heller, 1934, head appendages, instar I: (3–4) antenna; (3) dorsal aspect; (4) ventral aspect; (5) mandible, dorsal aspect. AN, antenna; MN, mandible; sp, spinula. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bars = 0.1 mm.

FIGURES 6–9. Sandracottus femoralis Heller, 1934, head appendages, instar I: (6–7) maxilla; (6) dorsal aspect; (7) ventral aspect; (8–9) labium; (8) dorsal aspect; (9) ventral aspect. LA, labium; MX, maxilla. Numbers and lowercase letters refer to primary setae and pores, respectively; * = additional sensilla. Scale bars = 0.1 mm.

FIGURES 10–11. Sandracottus femoralis Heller, 1934, mesothoracic leg, instar I: (10) anterior surface; (11) posterior surface. CO, coxa; FE, femur; PT, pretarsus; TA, tarsus; TI, tibia; TR, trochanter. Numbers and lowercase letters refer to primary setae and pores, respectively; * = additional sensilla. Scale bar = 0.2 mm.

FIGURES 12–14. Sandracottus femoralis Heller,1934, instar I: (12–13) abdominal segment VIII; (12) dorsal aspect;(13) ventral aspect; (14) urogomphus, dorsal aspect. AB, abdominal segment VIII; UR, urogomphus. Numbers and lowercase letters refer to primary setae and pores, respectively. Spine-like spinulae on abdominal segment VIII not represented. Scale bars = 0.2 mm.

FIGURES 15–19. Sandracottus femoralis Heller, 1934, instar II: (15) parietale, ventral aspect; (16) antennomere I, dorsal aspect; (17) mandible, ventral aspect; (18) maxilla, dorsal aspect; (19) prementum, ventral aspect. Scale bars = 0.5 mm (Fig. 15), 0.1 mm (Figs 16–19).

FIGURES 20–21. Sandracottus femoralis Heller, 1934, instar II, mesothoracic leg: (20) anterior surface; (21) posterior surface. Scale bar = 0.2 mm.

FIGURES 22–24. Sandracottus femoralis Heller, 1934, instar III: (22) lateral habitus; (23) head capsule. dorsal aspect; (24) abdominal segments VII–VIII, dorsal aspect. Photos by Y. Alarie.

FIGURES 25–29. Sandracottus femoralis Heller, 1934, instar III: (25) parietal, ventral aspect; (26) antenna, dorsal aspect; (27) maxilla, dorsal aspect; (28–29) mesocoxa and mesotrochanter: (28) anterior surface; (29) posterior surface. Scale bars = 0.5 mm (25) and 0.2 mm (26–29).

FIGURE 30. Pool formed by the drying up of a stream on a clay bed covered with decaying leaves and twigs in Solomon Islands, Guadalcanal where larvae of Sandracottus femoralis Heller, 1943 were collected. Photo by J. Hájek.