Platambus Thomson 1859
Creators: name: Okada, Ryohei
name: Alarie, Yves
name: Michat, Mariano C.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Dytiscidae
Platambus

description: Description of the larvae of Platambus Thomson, 1859
Diagnosis. Larvae of Platambus are characterized by the following combination of characters: cephalic capsule with neck constriction (Figs 1, 2, 15, 16, 29, 30, 43, 44, 57–60); occipital suture absent; pore FRe absent (Figs 1, 15, 29, 43); A3 lacking a ventroapical spinula, A3’ protruding, bulge-like to finger-like (Figs 4, 18, 32, 46); galea present, stipes with additional setae present or absent (Figs 5–6, 19–20, 33–34, 47–48); prementum broader than long (Figs 7–8, 21–22, 35 –36,49–50); legs lacking natatory setae (Figs 61–68); femur with several additional setae (Figs 10–11, 24–25, 38–39, 52–53); setae FE5, TI6 and TI7 short, spine-like (Figs 11, 25, 39, 53); LAS subquadrate, siphon lacking (Figs 12–13, 26–27, 40–41, 54–55, 69–72); urogomphi composed of one urogomphomere, lacking secondary setae, with primary seta UR5 much shorter than seta UR 7 in instar I larva (Figs 14, 28, 42, 56).
Instar I(Figs 1–56, 73–75). Body. Subcylindrical, narrowing towards abdominal apex. Measurements and ratios that characterize the body shape are shown in Table 3.
Head. Head capsule (Figs 1–2, 15–16, 29–30, 43–44). HL = 0.64–0.92 mm; HW = 0.59–0.75 mm; FRL = 0.22–0.41 mm. Flattened, rounded or subovate, about as broad as long (HL/HW = 1.04–1.27), maximum width at level of stemmata, sides subparallel or slightly diverging posteriorly; neck constriction present; occipital suture absent; ecdysial line well marked, coronal line long, 0.45–0.65 times HL; occipital foramen broadly emarginate ventrally, HW/OCW = 1.74–2.47; frontoclypeus subtriangular, rounded mesally, extending medially beyond level of anterolateral lobes of frontoclypeus [= adnasalia of Beutel (1994)]; dorsal surface with two spine-like egg bursters [= ruptor ovi of Bertrand (1972)] posteriorly, less than half as broad basally than maximum width of antennomere 1; anterior margin with 10–16 spatulate setae [= lamellae clypeales of Bertrand (1972)] variable in size; gular suture not visible; ocularium present, with six stemmata, four visible dorsally and two ventrally, arranged into two curved vertical rows; tentorial pits visible ventrally on each side at about mid-length. Antenna (Figs 3–4, 17–18, 31–32, 45–46). Slender, shorter than HW (A/HW = 0.60–0.83), composed of four antennomeres; A1 and A4 the shortest (A4/A1 = 0.83–1.37); A3 the longest (A4/A3 = 0.58–0.94); A3’ protruding, bulge- or finger-like. Mandible (Figs 9, 23, 37, 51). Prominent, broad basally, distal half projected inwards, sharp apically, 0.44–0.53 times as long as HL; mandibular channel present. Maxilla (Figs 5–6, 19–20, 33–34, 47–48). Cardo small, subovate; stipes short, broad, with minute spinulae proximad to galea; galea well developed, subconical, lacinia absent; palpifer short, palpomere-like, with dorsodistal spinulae; palpus 3-segmented, shorter than antenna (A/MP = 1.13–1.37), MP1 and MP2 the shortest, subequal, MP3 the longest (MP3/MP2 = 1.51–2.06). Labium (Figs 7–8, 21–22, 35–36, 49–50). Prementum subrectangular, broader than long, with minute spinulae on dorsal and ventral surfaces; palpus elongate, 2-segmented, subequal to shorter than maxillary palpus (MP/LP = 1.08–1.47); LP2 longer than LP1 (LP2/LP1 = 1.17–2.00).
Thorax. Terga convex, pronotum slightly shorter than meso- and metanotum combined, meso- and metanotum subequal, wider than pronotum; protergite subrectangular, margins rounded, more developed than meso- and metatergites; meso- and metatergites transverse, with anterotransverse carina; sagittal line visible on the three tergites; thoracic sterna membranous, spiracles absent. Legs (Figs 10–11, 24–25, 38–39, 52–53). Long, well developed, composed of six segments (including pretarsus), L1 the shortest, L3 the longest; L3 = 1.61–2.37 mm, L3/HW = 2.66–3.48; CO robust, elongate, TR divided into two parts, FE, TI and TA slender, subcylindrical; pretarsus with two long, slender, slightly curved claws, posterior claw shorter than anterior one on L1 and L2, claws subequal in length on L3; claws lacking basoventral spinulae; TI and TA with marginal spinulae variably developed.
Abdomen. 8-segmented; segments I–VII sclerotized dorsally, membranous ventrally; tergites I–VII narrow, transverse, rounded laterally, with sagittal line, with anterotransverse carina, covered with minute spinulae in transverse rows; spiracles absent on segments I–VII; LAS (Figs 12–13, 26–27, 40–41, 54–55). Short, subquadrate, completely sclerotized, ring-like, with anterotransverse carina dorsally and laterally (LAS = 0.16–0.27 mm, LAS/HW = 0.25–0.37), covered with minute spinulae in transverse rows; siphon reduced to almost lacking. Urogomphi. (Figs 14, 28, 42, 56). U = 0.70–1.17 mm, U/HW = 1.18–1.68, one-segmented, longer than LAS (U/LAS = 4.11–6.00), without or with microspinulae.
Chaetotaxy (Figs 1–56). Similar to that of generalized Agabinae larva (Alarie 1995, 1998; Alarie & Larson 1998; Alarie et al. 1998, 2019; Michat & Archangelsky 2009) except for the following characteristics: seta FR5 close to pore FRd; pore ANi located more distally; A3 with one minute structure (possibly a spinula) posterior to seta AN2; a minute structure (possibly a pore) present on dorsal surface of A4; prementum with one or two additional setae on dorsal surface; seta FE1 inserted sub-medially; seta FE6 hair-like; femora with a variable number of additional setae (Table 1); despite thorough effort setae AB7 and AB14 could not be found, so they were coded as absent but with some hesitation; setae UR2 and UR3 contiguously inserted; seta UR4 either contiguously inserted to setae UR2 and UR3 or more distant; pore URc and one additional minute seta located near the articulation of setae UR5–UR8; setae UR5 and UR6 shorter than setae UR7 and UR8.
Instar II (Figs 76–78). As first-instar larva except as follows:
Head. HL = 0.95–1.35 mm; HW = 0.85–1.14 mm; FRL = 0.40–0.56 mm. Head capsule. Subovate to subtrapezoidal (HL/HW = 1.11–1.24, HW/OCW = 1.88–2.30); frontoclypeus with 20–31 spatulate setae; egg bursters lacking. Antenna. A/HW = 0.60–0.72; A4 the shortest, A3 the longest (A4/A3 = 0.44–0.66). Maxilla. MP3 the longest (MP3/MP2 = 1.17–1.54); Labium. MP/LP = 1.10–1.29; LP2 subequal or longer than LP1 (LP2/LP1 = 1.00–1.47).
Thorax. Legs. L3 = 2.56–3.64 mm, L3/HW = 2.89–3.43.
Abdomen. Segment VII completely sclerotized, ring-like; LAS = 0.34–0.57 mm, LAS/HW = 0.38–0.52. Urogomphi. U = 1.29–1.69 mm, U/HW = 1.27–1.62, longer than LAS (U/LAS = 2.56–4.12); U5, U6, U7 and U8 subequal or U8 slightly shorter than the others.
Chaetotaxy. Cephalic capsule with several minute secondary setae; parietale with 4–8 spine-like secondary setae on the lateral margin and several spine-like setae on ventral surface; mandible with one hair-like secondary seta along external margin, proximal to pore MNa, and some minute secondary setae along external margin; stipes with one minute secondary seta on ventral surface, near setae MX 2 and MX 3; prementum with one secondary pore on ventral surface, near seta LA1; CO with one secondary pore on posterior surface; LAS with numerous secondary setae on dorsal and lateral surfaces; secondary leg setation represented in Table 2.
Instar III (Figs 57–72, 79–82). As second-instar larva except as follows:
Head (Figs 57–60). HL = 1.40–1.99 mm; HW = 1.21–1.64 mm; FRL = 0.61–0.77 mm. Frontoclypeus with 26–51 spatulate setae in a double low along anterior margin. Antenna, A1, A2 and A3 the longest, subequal (A4/A3 = 0.29–0.53); A3’ bulge-like. Maxilla. MP1, MP2 and MP3 subequal in length; Labium. LP2 shorter to longer than LP1 (LP2/LP1 = 0.73–1.20).
Thorax. Spiracular openings present on mesothorax. Legs (Figs 61–68). L3 = 3.87–5.51 mm, L3/HW = 3.03– 3.81.
Numbers between slash marks refer to pro-, meso- and metathoracic leg, respectively.
......continued on the next page
Abdomen. Spiracular openings present on segments I–VII; LAS = 0.73–1.12 mm, LAS/HW = 0.55–0.77. Urogomphi (Figs 69–72). U = 1.88–2.78 mm, U/HW = 1.24–1.84; U/LAS = 1.88–2.86.
Chaetotaxy (Figs 57–72). Stipes with 1–2 minutes secondary setae; prementum with two secondary pores; CO with two secondary pores; Secondary leg setation represented in Table 1 and Figures 61–68.
description: Published as part of Okada, Ryohei, Alarie, Yves & Michat, Mariano C., 2019, Description of the larvae of four Japanese Platambus Thomson, 1859 (Coleoptera: Dytiscidae: Agabinae) with phylogenetic considerations, pp. 401-433 in Zootaxa 4646 (3) on pages 403-406, DOI: 10.11646/zootaxa.4646.3.1, http://zenodo.org/record/3351180