Huosoma latiloba (Yu, Yang & Bu, 2008)

Yang, Guo-Hui, Orr, Albert G. & Zhang, Hao-Miao, 2022, Descriptions of the larvae of Huosoma Guan, Dumont, Yu, Han & Vierstraete 2013 from China (Odonata: Coenagrionidae), Zootaxa 5134 (3), pp. 426-434 : 427-428

Huosoma latiloba (Yu, Yang & Bu, 2008)

( Figs 1 , 2a ; 3a–n ; 5 ; 7a )

Material examined. 1♀, 2♂♂ larvae, 6.X.2020, Huadianba (25.54°N, 100.00°E, 2,920 m a.s.l.), XiZhou Town , Dali City, Yunnan Province, China, Guo-Hui Yang leg. Huadianba is on Mt Cangshan in Dali, Yunnan. There are many streams and pools in the surrounding mountains . 1♀ and 1♂ larvae were collected and successfully raised to emergence.

Habitus: Body small (body length including caudal lamellae 15–18mm long), smooth and moderately stout, lacking distinct bands or marks, with broad paddle-shaped caudal lamellae ( Figs 1 , 7a ). Males and females are very similar except for presence of an ovipositor in the latter.

Head: Wider than long, maximum width 1.9–2.1 times length. Compound eyes black and prominent. Occiput light brown, with occipital lobes rounded but rather bulbous ( Fig. 2a ); antenna filiform, 7–segmented, length of successive antennal segments (mm): 0.10, 0.10, 0.25, 0.35, 0.25, 0.25, 0.3 ( Fig. 3a ). Labium ochreous, prementum basally narrow, anteriorly expanded strongly and nearly evenly; anterior margin strongly projected as obtuse isosceles triangle, apex forming 115° angle (dorsal view), with fine marginal denticles; prementum length about 4.1 times wider than base, maximum breadth 0.7 length; row of 3–4 long, strong setae sub-medially on upper side of prementum (N=3) ( Figs 3b, c ). Labial palp long and narrow, distinctly expanded apically, upper margin with eight very long, strong setae set in raised sockets ( Fig. 3d ); movable hook incurved, but only ca 3/5 length of longest palpal seta ( Figs 3d , 5 ); palp terminating in broad securiform ‘comb’ separated by shallow notch from short ventral hook slightly exceeding margin of comb in length. Mandibles brown, teeth black blown, formula: L 1+234+50y ab R 12345 ab, molar crest absent both right and left mandibles, incisor teeth rounded, 2> 3> 5> 4> 1, additional tooth y on the right mandible ( Figs 3e–h ). Maxillae long, with dense long setae present on the distal one-thirds of its length ( Figs 3i–j ).

Thorax. Brown, smooth without distinct bands or marks. Prothorax rectangular. Synthorax trapezoidal and elongate. Legs moderately long and slender, the femur of hind leg reaching to middle of S4. Wing cases parallel, outer wing cases reach to the hind margin of S4, inner cases a little shorter.

Abdomen. Brown, smooth with black brown markings. Lateral spines absent. Ovipositor of female extending beyond the end of S10 ( Figs 3k–l ). Caudal lamellae half as long as abdomen, broadly paddle-shaped ending in a short white filament, especially on outer lamellae, margins with well separated low serrations; surface marked with irregular black blotches, especially visible near base. Maximum length:width ratio 2.6 in lateral lamellae and 2.4 in median lamella ( Figs 3m –n ).

Measurements (mm). Larvae (N=3), body length (excluding caudal lamellae) 12–13.5; length of abdomen (excluding caudal lamellae) 8–9; maximum head width 2.5–2.8; length of hind femur 3.5–4; lateral caudal lamella 4.5–5.

Biological notes. The larva of H. latiloba was found in a pool in a small mountain stream, with numerous hydrophytes ( Fig. 7a ). Breeding adults often appear at the edge of nearby streams ( Fig. 6c ). The flight season ranges from June to September.

Figures

FIGURE 1. Final instar larva H. latiloba habitus.

FIGURE 2. Heads of larvae of two species of Huosoma in dorsal view. (a) H. latiloba; (b) H. tinctipenne.

FIGURE 3. Morphological details of the final stadium larva of H. latiloba: (a) left antenna; (b) prementum, ventral view; (c) same, dorsal view; (d) right labial palp, inner surface; (e) right mandible, posterior view; (f) same, inner surface; (g) left mandible, posterior view; (h) same, inner surface; (i) left maxilla; (j) right maxilla; (k) female ovipositor, lateral view; (l) same, ventral view; (m) lateral lamella, lateral view; (n) median lamella, lateral view.

FIGURE 5. Labial palp of Huosoma latiloba: left, anterior view in situ on prementum; right, showing detail, (a) inner length of comb; (b) width of comb; (c) palpal hook (measurement terminology corresponding with Brochard & van der Ploeg 2013).

FIGURE 6. Labial palp of Huosoma tinctipenne: left, anterior view in situ on prementum; right, showing detail, (a) inner length of comb; (b) width of comb; (c) palpal hook (measurement terminology corresponding with Brochard & van der Ploeg 2013).

FIGURE 7. Larvae and adults of two Huosoma species: (a) male larva of H. latiloba; (b) emerging adult male of H. latiloba; (c) mating pair of H. latiloba, Mt. Cangshan, Dali City, Yunnan Province (photo by Guo-Hui Yang); (d) larva of H. tinctipenne ready to feed on the larvae of Chironomidae; (e) final stadium larva of H. tinctipenne; (f) adult female of H. tinctipenne, Yunlong County, Dali City, Yunnan Province (photo by Guo-Hui Yang).