Tropisternus (Pristoternus) ovalis Castelnau, 1840

Torres, Patricia L. M., Michat, Mariano C., Archangelsky, Miguel & Fernández, Liliana A., 2014, Description of immatures of the genus Tropisternus Solier, subgenus Pristoternus Orchymont (Coleoptera: Hydrophilidae), with emphasis on the chaetotaxy and morphometry of larval forms, Zootaxa 3790 (2), pp. 380-398 : 388-392

publication ID

https://dx.doi.org/10.11646/zootaxa.3790.2.6

publication LSID

lsid:zoobank.org:pub:9CE1C14D-7C9D-4480-BC43-F556259CF118

DOI

https://doi.org/10.5281/zenodo.5613783

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https://treatment.plazi.org/id/038987BE-5A39-FFB6-1BCA-7006FC375ABB

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scientific name

Tropisternus (Pristoternus) ovalis Castelnau, 1840
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Tropisternus (Pristoternus) ovalis Castelnau, 1840

( Figs. 3 View FIGURES 1 – 6 , 20– 31 View FIGURES 18 – 21 View FIGURES 22 – 28 View FIGURES 29 – 31 )

Material examined. Three egg cases, 8 larvae of instar I, 3 of instar II, 4 of instar III and 2 pupae were used for the descriptions. Breeding adults were collected at the following locality: Argentina: Corrientes Province, Mburucuyá National Park, I- 2008 (see Fig. 1 View FIGURES 1 – 6 in Torres et al. 2012).

Description, egg case ( Fig. 3 View FIGURES 1 – 6 ). Whitish, saccular, subcircular in cross section. Mast absent. Length = 3.7–3.9 mm, width = 3.5–3.7 mm, height = 2.6–2.8 mm; cap length = 2.2–2.5 mm.

Description, instar I ( Figs. 22–31 View FIGURES 22 – 28 View FIGURES 29 – 31 ). Color: head capsule testaceous, with yellowish areas around frontal sulci and on dorsolateral surface of parietale. Cephalic and thoracic appendages testaceous. Thoracic tergites testaceous with yellowish scattered maculae; thoracic sternites testaceous. Body: for morphometric measurements and ratios see Table 2 View TABLE 2 . Head capsule ( Figs. 22–24 View FIGURES 22 – 28 ): nasale with 7–8 teeth on anterior margin, without anteroventral denticles ( Fig. 24 View FIGURES 22 – 28 ). Mandibles ( Figs. 27–28 View FIGURES 22 – 28 ): distal tooth of retinaculum bifid or unifid apically, outer lateral surface slightly serrate. Labium ( Figs. 25–26 View FIGURES 22 – 28 ): anterolateral angles of mentum strongly projected forward. Dorsal surface of mentum with strong spinulae, central area with some scattered spinulae. Dorsal surface of second labial palpomere without spinulae. Chaetotaxy. Antenna ( Fig. 29 View FIGURES 29 – 31 ): seta AN 8 present.

Description, instar II. As instar I except for the following features. Color: head capsule with some maculae present around frontal sulci and on dorsolateral surface of parietale. Body: for morphometric measurements and ratios see Table 2 View TABLE 2 . Head capsule: nasale with two anteroventral denticles. Chaetotaxy. Head capsule: with 17–18 secondary setae distributed in the area between FR 1 and PA 7, and near PA 18. Outer gFR 2 setae spiniform. Mandibles: with 2 short secondary setae at the base and 29–35 secondary minute sensilla distributed mainly along dorsolateral surface. Antenna: A 1 with numerous secondary setae arranged as follows: 6–7 short setae on ventral surface, 2 slender setae and 14–15 stout spiniform setae on inner lateral surface, 6–7 setae on outer lateral surface, and two distal rings of long setae, apical one with 3 setae, the other with 7–8 setae. Maxilla: outer lateral surface of stipes with 2–4 hair-like secondary setae at the base, and 17–20 secondary setae unevenly distributed. Outer lateral surface of MP 1 with 1 distal secondary seta. Labium: Mt with 1 stout secondary seta on each anterolateral angle, 4–6 secondary setae on laterobasal surfaces, 10–12 stout secondary setae on dorsal surface, and 4–6 thin secondary setae on ventral surface.

Description, instar III. As instar II except for the following features. Body: for morphometric measurements and ratios see Table 2 View TABLE 2 . Chaetotaxy. Head capsule: 18–19 secondary setae with similar distribution as in instar II. Mandibles: with 2 short secondary setae at the base and 29–40 secondary minute sensilla distributed mainly along dorsolateral surface. Antenna: A 1 with numerous secondary setae arranged as follows: 4–7 short setae on ventral surface, 1–2 slender setae and 14–15 stout spiniform setae on inner lateral surface, 4–5 setae on outer lateral surface, and two distal rings of long setae, apical one with 3 setae, the other with 7–9 setae. Maxilla: outer lateral surface of stipes with 2–3 hair-like secondary setae at the base, and 14–18 secondary setae unevenly distributed. Labium: Mt with 1 stout secondary seta on each anterolateral angle, 6–9 secondary setae on laterobasal surfaces, 10–13 stout secondary setae on dorsal surface, and 6–10 thin secondary setae on ventral surface.

Description, pupa ( Figs. 20–21 View FIGURES 18 – 21 ). Similar to the pupa of T. latus except for the following features. Body: TL (excluding pronotal styli and cerci) = 5.0– 5.8 mm; MW = 2.8–3.1 mm. Thorax: pronotum with 18–19 styli distributed as follows: 4 on pronotal disc and 14–15 on lateral surfaces (8 large styli anteriorly, 2 on each posterolateral angle, and 4–5 styli posteriorly). Metasternal spine short. Abdomen: segments II–VII with 6 styli (4 in a transverse row on each tergum and 1 about six times longer on each pleural area); segment IX with 2 short, apically unifid cerci; segments II–VI with lateral tubercles or horn-like projections.

TABLE 2. Measurements (in mm) and ratios for the three larval instars of Tropisternus ovalis.

Measure Instar I Instar II Instar III
TL 3.30–3.50 4.00–7.50 10.50–12.00
MW 0.60–0.80 0.70–1.50 1.80–1.90
HL 0.46–0.47 0.60–0.72 0.85–0.89
HW 0.58–0.61 0.74 1.10–1.14
HL/HW 0.76–0.78 0.72–0.86 0.75–0.81
AL 0.50–0.51 0.71–0.73 0.84–0.91
A1L 0.28–0.29 0.46–0.47 0.57–0.61
A2L 0.12–0.13 0.14–0.15 0.14–0.16
A3L 0.10 0.11–0.12 0.13–0.14
A1L/(A2L+A3L) 1.22–1.26 1.77 2.07–2.15
HL/AL 0.90 0.83–0.86 0.93–1.06
HW/AL 1.16–1.19 1.16 1.25–1.31
SL 0.36–0.38 0.54–0.57 0.74–0.75
MPL 0.37 0.45–0.47 0.52–0.56
SL/MPL 0.96–1.00 1.21–1.22 1.32–1.45
MP1L 0.11 0.14–0.15 0.16–0.17
MP2L 0.03–0.04 0.04–0.05 0.06
MP2W 0.04 0.04 0.04–0.05
MP3L 0.11 0.14 0.16–0.18
MP4L 0.11–0.12 0.13 0.14–0.15
MP2L/MP2W 0.82–0.89 1.00–1.11 1.30–1.33
ML 0.73–0.75 0.99–1.01 1.27–1.31
LPL 0.11 0.13–0.14 0.15
LP1L 0.02 0.02–0.03 0.03–0.04
LP2L 0.08–0.09 0.10–0.11 0.11–0.12
LP2L/LP1L 3.40–3.60 3.67–4.20 2.75–4.00
LigL/LPL 0.54–0.57 0.46–0.58 0.63–0.67
MtW 0.17 0.25–0.26 0.36–0.38
PrmtW/PrmtL 0.99–1.00 0.85–0.88 0.72–0.75
PrmtW/MtW 0.52–0.54 0.40–0.45 0.32–0.36
LEG 1 L 1.19–1.27 1.72–1.75 2.38–2.44
LEG 2 L 1.25–1.34 1.77–1.89 2.53–2.57
LEG 3 L 1.43–1.44 1.95–2.00 2.85–2.90
LEG 3/LEG 1 1.13–1.20 1.13–1.14 1.17–1.22
LEG 3/LEG 2 1.07–1.15 1.06–1.10 1.11–1.14
LEG 1 (TITA/FE) 0.80–0.88 0.75–0.78 0.75–0.76
LEG 2 (TITA/FE) 0.79–0.81 0.69–0.73 0.68–0.70
LEG 3 (TITA/FE) 0.82–0.87 0.75–0.77 0.68–0.72
LEG 1 (CL/TITA) 0.63 0.54 0.45–0.48
LEG 2 (CL/TITA) 0.53–0.72 0.57–0.61 0.49–0.54
LEG 3 (CL/TITA) 0.63–0.64 0.49–0.55 0.51