Libellago hyalina
Creators: name: Orr, Albert G. W.
name: Dow, Rory A.
name: Steinhoff, Philip O. M.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Chlorocyphidae
Libellago
Libellago hyalina

description: Libellago hyalina (Selys)
(Figs 4d, 5d, 7d, 8d, 9d, 11c, d, h, 14e,f, 15f, g, 16c, e, 17c, d, 18d)
Material examined. MALAYSIA, 1 ♂ F, 1 ♀ F (RMNH. INS.229046, RMNH. INS.229063), small stream in alluvial forest, park headquarters area, Gunong Mulu National Park, Miri Division, Sarawak, 4.0506N, 114.8148E, 7 i 2008 (RMNH. INS.229046), 15 i 2008 (RMNH. INS.229063), leg. S.G. Butler. BRUNEI, 1 ♂ F, supposition, in runnel in peat swamp forest near Sg. Badas, 4.57124N, 114.42616E, 23.v.1995, A.G. Orr leg.
Habitus: similar to H. biseriata but obviously smaller than both that species, and S. petiolata. Abdomen slightly more swollen. Differences in pattern of mottling on head and body may be significant but are difficult to define; antennae relatively shorter than other species and lacking dark spot at apex of pedicel. Caudal gills, very thin, strongly tapered and long.
Head: sagittate in dorsal view but long axis slightly shorter in proportion to head width than in other species (Fig. 5d) and less deep in lateral aspect (Fig. 7d). Antennae 7-segmented but relatively short (1.11 times maximum head width); scape with mainly longer setae; pedicel lacking dark apical mark. Labrum as in H. biseriata but slightly more rounded with only 9–10 setae on the ‘moustache’. Genae with collection of very small sub-acute tubercles (Fig. 7d). Mask short, articulation resting between posterior part of coxae of prothorax (Fig. 8d); prementum narrow basally, gradually flared anteriorly with margins of anterior half slightly convex; lateral margins with strong recurved spines on distal 2/3 rd (Fig. 9d) interspersed with short setae (Fig. 11c); anterior median lobe as in H. biseriata but median cleft long with sides closely appressed; inner (lower) branch of palpal lobe strongly hooked (Fig. 11c); maxillae (Fig. 12d) very similar to H. biseriata, but two sub-basal supplementary spines on major (4 th) apical spine well separated and all three supplementary spines relatively longer and thinner (Fig. 12h). Mandibles (Figs 14e, f, 15e, f) lacking supplementary denticles, right with four well defined teeth on incisor lobe with small shoulder dorsally, ventrally with subapical marginal denticle as usual; molar crest on right well developed with two small short sharp denticles, lower one with narrow chisel tip (Figs 14e, 15f); left incisor lobe with five regular evenly spaced teeth; left molar crest broad and raised, rather flat ending in straight edge with 9 denticles, end ones distinctly longer, (Figs 14f, 15e). A strong outer basal seta on both mandibles as in other three species (not visible in 14e).
Thorax: prothorax saddle-shaped with anterior and posterior flanges as in other species (Fig. 5d), but relatively narrower and with both pairs of dorsal tubercles broad based and large. Marking (not illustrated) indistinct but always with narrow pale band pale between two anterior tubercles on prothorax. Wing sheaths slightly spatulate, not completely obscuring abdomen at sides, forewing reaching middle of S6, hindwing almost to hindmargin of S6 (Fig. 4d). Legs long and thin, metafemur almost reaching hindmargin of S7, proportions similar to H. biseriata; two rows of pectinate setae on the venter of the tarsus.
Abdomen: squat and swollen medially, dark with indistinct dark mottling (not figured). Ventrolateral margin of S9 with 6–9 strong, curved spines but no significant spines on venter or ventral margin (Figs 16c, 17c, d); S10 with 4–5 strong ventrolateral spines and 4–6 smaller spines on hind-margin S10 (Figs 16c, e, 17c, d). Male gonapophyses (Fig. 17c,d) short and conical, well separated, arising near posterior margin S9 and reaching beyond hind margin. Outer female gonapophyses (Figs 16c, e) arising from near base of S9 and extending beyond hind margin of S10 to about level of epiproct tip (Fig. 16e), ventral margin with series of sparse heavy spines to about level of midpoint of S10, thence continuing slightly upward to a sharp point, aligned with inner apophyses but terminating before tip of latter (Fig. 16e); inner apophyses smooth, curved smoothly and upward to a rounded point extending only a little beyond outer apophyses and epiproct. Epiproct, short, subconical, not obviously different from other species studied. Caudal spikes about 65% body length, slightly swollen at base then thin and tapered almost uniformly to a point (Fig. 18d); bearing numerous backward facing sharp curved spines, heavy setae, and also long fine setae impossible to assess accurately.
Measurements (in mm): body length excluding antennae, caudal appendages and gills 9.3; lateral caudal gills 5.2; head width 2.57; prementum 1.45; palpal lobe (to tip of dorsal branch) 0.49; movable hook 0.37; maxillae base to distal hook of galeolacinea (1.15), maxillary palp (0.46); mandibles long axis (0.64); antenna 1.17, 0.45, 0.45, 0.30, 0.25, 0.15, 0.09 (total 2.86).
Remarks. Larvae of L. hyalina are easily distinguished from the other three species studied by their size, their shorter prementum with strong lateral spines and by the lack of any dark coloration at the tip of the pedicel. The long thin caudal spikes with slight basal swelling thence evenly tapered to a point are also distinctive. They differ from S. petiolata rather subtly in the form of the caudal spikes which are thinner and slightly bulbous at base, and in having much shorter antennae, far fewer spines on the venter of the terminal abdominal segments, and in the shorter female genital apophyses with the outer aligned with the inner. As a rule the inner mouthparts, the mandibles and maxillae are extremely conservative and therefore it is noteworthy that distinct differences were found between L. hyalina and the other genera studied, especially in the left mandible. These characters are however difficult to observe and not particularly useful for diagnosis.
description: Published as part of Orr, Albert G. W., Dow, Rory A. & Steinhoff, Philip O. M., 2024, Descriptions of larvae of four mainly DNA barcode-matched species of chlorocyphids from south-east Asia (Odonata: Chlorocyphidae) with notes on the generic and species level larval identification of Oriental region members of the family., pp. 301-337 in Zootaxa 5486 (3) on pages 324-327, DOI: 10.11646/zootaxa.5486.3.1, http://zenodo.org/record/13210005