Neobidessodes limestoneensis (Watts & Humphreys)

Michat, Mariano C., Alarie, Yves & Watts, Chris H. S., 2010, Descriptions of the first-instar larva of the hypogaeic species Neobidessodes limestoneensis (Watts & Humphreys) and of the third-instar larva of Hydroglyphus balkei Hendrich (Coleoptera: Dytiscidae: Bidessini) with phylogenetic considerations, Zootaxa 2658, pp. 38-50 : 40-42

Neobidessodes limestoneensis (Watts & Humphreys) , first-instar larva

Source of material. Australia, Yilgarn, WA; Limestone Well, Three Rivers Station, 25°16’59’’S, 119°10’33’’E, 26/viii/2001; W. F. Humphreys, T. Karanovic & J. M. Waldock (Watts & Humphreys 2003).

Diagnosis. Body relatively soft, lightly sclerotized; occipital suture absent ( Fig. 1 ); occipital foramen small ( Figs 1–2 ); anteroventral margin of nasale with 14 digitiform lamellae clypeales ( Fig. 2 ); stemmata absent ( Fig. 1 ); A3 with a ventroapical spinula ( Fig. 4 ); mandible elongate, slender ( Fig. 5 ); MP longer than antenna; claws short ( Figs 10–11 ); pore PAj absent ( Fig. 2 ); ratios HL/HW, A3/A1, MNL/MNW, A/MP, MP2/ MP1, LP2/LP1, LAS/HW, U/LAS and U1/U2 ( Table 1 ).

limestoneensis balkei limestoneensis balkei

Instar I (n = 1) Instar III (n = 3) Instar I (n = 1) Instar III (n = 3)

HL (mm) 1.00 0.78–0.80 MP2/MP3 3.67 2.55–3.00 Description. Color. Uniformly pale, unpigmented, distal half of mandible light brown.

Body. Relatively soft, lightly sclerotized, subcylindrical, narrowing towards abdominal apex. Measurements and ratios that characterize the body shape are shown in Table 1 .

Head. Head capsule ( Figs 1–2 ). Longer than broad; surface spinulae absent; maximum width at level of egg bursters, without neck constriction; occipital suture absent; ecdysial line slightly visible, coronal line relatively short; occipital foramen small, broadly emarginate ventrally; posterior tentorial pits visible ventrally; FR elongate, lateral margins sinuate, with two lateral, spine-like egg bursters at mid-length; nasale moderately elongate, subtriangular, rounded apically, sinuate laterally, with one small branch at each side; ventrodistal surface with spinulae of different shapes, ventrolateral margin with robust spinulae ( Fig. 2 ); anteroventral margin of nasale with a half circle of 14 digitiform lamellae clypeales of different lengths, directed downward; stemmata absent. Antenna ( Figs 3–4 ). Elongate, composed of four antennomeres, shorter than HW; A1 and A4 the shortest, subequal, A3 the longest, with a ventroapical spinula; A3’ elongate.

Mandible ( Fig. 5 ). Elongate, slender, distal half projected inwards and upwards, apex sharp; mandibular channel present. Maxilla ( Figs 6–7 ). Cardo fused to stipes; stipes short, broad; galea and lacinia absent; MP very elongate, longer than antenna, composed of three palpomeres, MP3 the shortest, MP2 the longest. Labium ( Figs 8–9 ). Prementum small, subtrapezoidal, somewhat broader than long, without lateral spinulae, anterior margin slightly indented medially; LP elongate, composed of two palpomeres; LP2 markedly constricted at mid length, longer than LP1.

Thorax. Terga convex, pronotum slightly shorter than meso- and metanotum combined, meso- and metanotum subequal; protergite subovate, more developed than meso- and metatergite; meso- and metatergite transverse, covered with minute spinulae in transverse rows; all sclerites without anterotransverse carina; sagittal line not visible; sterna membranous; spiracles absent. Legs ( Figs 10–11 ). Long, composed of six articles sensu Lawrence 1991), L1 the shortest, L3 the longest; CO elongate, TR short, divided into two parts, FE, TI and TA slender, subcylindrical, PT with two short, robust, slightly curved claws; posterior claw shorter than anterior claw on L1 and L2, posterior claw longer than anterior claw on L3; TA and anterior surface of CO, mesoTI and metaTI covered with minute slender spinulae in transverse rows; ventral surface of TA and to a lesser extent TI with elongate spinulae.

Abdomen. Eight-segmented; segments I–VI sclerotized dorsally, membranous ventrally; segment VII completely sclerotized, ring-like (difficult to assess due to the lightly sclerotized body); tergites I–VI narrow, transverse, rounded laterally, sagittal line not visible; all sclerites without anterotransverse carina, covered with minute spinulae in transverse rows; spiracles absent on segments I–VII; LAS ( Figs 12–13 ) the longest, completely sclerotized, ring-like, covered with minute spinulae in transverse rows; siphon short, subconical. Urogomphus ( Fig. 14 ). Long, composed of two urogomphomeres; U1 longer than LAS, covered with minute spinulae in transverse rows; U2 narrow, setiform, shorter than U1.

Chaetotaxy. Similar to that of generalized Hydroporinae larva (Alarie & Harper 1990; Alarie et al. 1990; Alarie 1991; Alarie & Michat 2007) except for the following features: pore FRc submarginal, contiguous to seta FR7; pores PAd, PAe and PAj absent; pore PAg present; pore ANf absent; pore ANh distal; setae MX 4, MX 8, MX 9 and MX 10 absent; seta MX 1 inserted on the stipes; seta LA7 absent; seta TR 2 absent; pore FEa absent; several setae on FE and TI multi-branched; seta TI7 short, spine-like; pores ABa and ABc absent; seta AB9 very long; seta AB10 spine-like; we were unable to find pore ABd and setae AB7 and AB8; however, we could not establish if they are really absent due to the presence of spinulae on the siphon; setae UR2, UR3 and UR4 inserted far from each other; setae UR5, UR6 and UR7 elongate; seta UR8 inserted distally.

Figures

FIGURES 1 – 14. Neobidessodes limestoneensis, first-instar larva. 1, cephalic capsule, dorsal aspect; 2, cephalic capsule, ventral aspect; 3, antenna, dorsal aspect; 4, antenna, ventral aspect; 5, mandible, dorsal aspect; 6, maxilla, dorsal aspect; 7, maxilla, ventral aspect; 8, labium, dorsal aspect; 9, labium, ventral aspect; 10, metathoracic leg, anterior aspect; 11, metathoracic leg, posterior aspect; 12, abdominal segment VIII, ventral aspect; 13, abdominal segment VIII, dorsal aspect; 14, urogomphus, dorsal aspect. EB, egg burster; Sp, spinula; TP, tentorial pit. Scale bars = 0.10 mm.

Tables

TABLE 1. Measurements and ratios for the larvae of Neobidessodes limestoneensis and Hydroglyphus balkei. Measure Neobidessodes Hydroglyphus Measure Neobidessodes Hydroglyphus

HW (mm) 0.62	0.60–0.65	MP/LP	1.44	1.30–1.44
FRL (mm) 0.80	0.59–0.60	LP2/LP1	1.33	1.12–1.18
OCW (mm) 0.19	0.43–0.46	L3 (mm)	1.99	1.66–1.79
HL/HW 1.62	1.24–1.30	L3/L1	1.44	1.29–1.31
HW/OCW 3.29	1.39–1.49	L3/L2	1.08	1.15–1.17
COL/HL 0.21	0.23–0.27	L3/HW	3.22	2.71–2.76
FRL/HL 0.79	0.73–0.77	L3 (CO/FE)	0.91	0.89–0.93
A/HW 0.66	0.61–0.66	L3 (TI/FE)	0.67	0.63–0.64
A3/A1 2.14	1.75–1.93	L3 (TA/FE)	0.76	0.63–0.64
A3/A2 1.36	0.97–1.07	L3 (CL/TA)	0.22	0.42–0.45
A4/A3 0.53	0.31–0.36	LAS (mm)	0.33	0.40–0.42
A3’/A4 0.94	0.70–0.78	LAS/HW	0.54	0.64–0.66
MNL/MNW 5.10	3.80–4.50	U (mm)	1.28	1.46–1.61
MNL/HL 0.53	0.47–0.50	U/LAS	3.85	3.65–3.88
A/MP 0.90	1.16–1.19	U/HW	2.06	2.40–2.49
MP2/MP1 1.26	0.82–0.93	U1/U2	2.49	1.73–2.26