Synchroa chinensis Nikitsky, 1999

Jiang, Ri-Xin, Huang, Xiu-Dong, Yang, Lin, Chang, Zhi-Min, Long, Jian-Kun & Chen, Xiang-Sheng, 2022, Description of the mature larva and pupa of Synchroa chinensis Nikitsky, 1999 (Coleoptera, Synchroidae), Zootaxa 5219 (1), pp. 83-91 : 84-88

Synchroa chinensis Nikitsky, 1999

Synchroa chinensis Nikitsky, 1999: 478–479 , figs 6–8. Type locality: China, Sichuan, Qingchengshan .

Distribution: China: Sichuan, Shaanxi, Gansu, Guizhou (new distributional record).

Specimens examined. Larvae (4 ex), pupae (2 ex), adults (8 ex, 2♂♂, 4♀♀). 2 larvae, 1 pupa, 3 adults (1♂, 2♀♀), labeled ‘ China: Guizhou, Guiyang City (aeffi市), Huaxi District ( AE Ḿ区), Shilihetan (十m河Ḃ), 05.III.2022, H: 1100 m, Ri-Xin Jiang leg.’ ( GUGC); additional label of pupa: 1ex, labeled ‘ 31.III.2022 pupated’; additional label of adults: 2 ex (1 ♂, 1♀), labeled ‘ 31.III.2022 pupated, 08.IV.2022 enclosed adult’; 1 ex (1♀), labeled ‘ 05.IV.2011 pupated, 12.IV.2022 enclosed adult’ . 2 larvae, 1 pupa, 5 adults (1♂, 4♀♀), labeled ‘ China: Guizhou, Guiyang City (aeffi市), Huaxi District ( AE Ḿ区), Huaxi Park ( AE Ḿ公园), 12.IV.2022, H: 1060 m, Ri-Xin Jiang & Xiu-Dong Huang leg.’ ( GUGC); additional label of pupa: 1 ex, labeled ‘ 16.IV.2022 pupated’; additional label of adults: 3 ex (1♂, 2ff #), labeled ‘ 18.IV.2022 pupated, 23.IV.2022 enclosed adult’; 2 ex (2ff #) labeled ’ 20.IV.2022 pupated, 27.IV.2022 enclosed adult’ .

Descriptions

Larva (mature stage). Body ( Fig. 1 ) elongate and nearly parallel-side, light brown both dorsally and ventrally, with antennae, labrum, clypeus, mandibles and urogomphi dark brown. Integument covered with scattered fine setae.

Head. ( Figs 2A–C ). Weakly prognathous, posterior edge of head capsule slightly emarginate; widest near basal 1/3 and weakly constricted anterior to occipital foramen, slightly narrower than prothorax; lateral sides rounded. Upper and lower surfaces of head shiny, dorsal surface modified with thin crease at anterior 1/3. Epicranial stem short; frontal arms U-shaped, about 2/3 length of head capsule, apical half sinuous and meeting a pair of dark brown spots; inner part of frontal arms with a pair of medium-length setae at middle. Frons smooth; epicranial plates light brown, surface smooth and modified with thin and shallow crease, and with sparse short and few long erect setae; lateral portion with both short and long erect setae, denser than dorsal part; ventral portion with several long erect setae and sparse short setae. Each side with five stemmata, anterior three located near antennal base. Frontoclypeal suture absent; clypeus dark brown, transverse, surface shiny with thin crease, and three pairs of long erect setae, the setae usually symmetrically distributed but asymmetrically in some specimens, apical margin weakly curved. Labrum ( Fig. 3A ) free, transverse, widest at middle; dorsal surface of labrum smooth; disc with three pairs of long erect setae; apical margin rounded protruded at middle, with three short setae, side parts with round margins, covered with several pairs of different length erect setae; lateral margins finely curved; ventral surface with a pair of medial spines; four pairs of sensory papillae symmetrically located ( Fig. 3B ) near medial spines; each side of apical margin with three short anterior spines. Antenna ( Fig. 2F ) 3-segmented; antennomere I shorter than antennomeres II and III, widest, narrower from base to apex; antennomere II and III about same in length; antennomere III with two sensoria, the larger one about half length of antennomere III, palpiform; another one much shorter than antennomere III, conical. Mandibles ( Figs 2D & E ) strong and simple, asymmetrical, broad at base and narrowing to apex; broadbased prostheca strong, anterior part distinctly projecting from left mandible, short and rounded on right mandible. Ventral mouthparts ( Figs 3C & D ) retracted; cardo transverse, divided by internal ridge; stipes distinctly longer than wide, disc with sparse setae of different lengths; apical and inner sides of mala setose, apical angle with several distinct unci. Maxillary palp 3-segmented, palpomere I longest, covered with several setae of different lengths; palpomere II and III about the same length, palpomere II with several setae near apex, palpomere III without setae and narrowing from base to apex, apically rounded. Submentum nearly trapezoidal, finely narrowed at middle. Mentum trapezoidal, widest at base, disc with a pair of long setae. Prementum nearly triangular, with a pair of long setae on disc, apex rounded; apical sclerome molar-like.

Thorax. Thoracic tergite transverse, pronotum longer than meso- and metanotum combined, light brown, surface shiny and modified with thin crease, disc with sparse short setae, laterally with long erect setae. Meso- and metanotum with patches of asperities, separated by median line, completely separated on mesonotum and apically confused on metanotum. Presternum well defined, short and near fusiform, basal margin rounded, disc with a pair of erect setae of medium length. Spiracles oval, prothorax and metathorax without spiracles. Coxal cavities widely separate.

Legs. ( Figs 4A–C ). Legs well developed, 5-segmented. Surface covered with dense setae of different lengths; setae on anterior part much shorter on average than on posterior part. Posterior parts of meso- and metacoxa, trochanter and femur covered with dense asperities associated with each seta.

Abdomen. Abdomen about three times as long as thorax. Tergites I–V covered with patches of asperities, separated by median line and confused near apex in tergites I–IV, not confused in tergite V. Other tergites and all sternites without asperities, covered with sparse setae of medium length. Sternite IX with a pair of small but well developed projections at base. Urogomphi simple, distinctly acute in lateral view, without spiracles.

Measurements (in mm; n = 4): HL: 1.81–2.07; HW: 2.85–3.10; PL: 1.97–2.17; PW: 3.06–3.39; MSL: 0.55– 0.67; MSW: 3.01–3.30; MTL: 0.91–1.08; MTW: 2.90–3.10; AT9L: 1.59–1.90; AT9W: 1.78–2.11.

Pupa (midterm development). Body ( Figs 5A–C ) mainly creamy-yellowish, dark brown at apices of mandible and urogomphi; eye, antenna and apical half of elytra brown. Dorsum slightly convex, sides subparallel to segment VII of abdomen.

Head. Head hypognathous ( Figs 5A–C , 6B ), hidden from dorsal view. Dorsal surface smooth and modified with transverse crease and sparse granules, bearing setae of different lengths. Frons and vertex covered with sparse granules bearing long erect setae, setae on other parts much shorter. Apical margin of clypeus straight, surface with 9 granules bearing short setae. Labrum nearly trapezoidal, with apical margin straight, surface covered with dense short and thin setae. Each eye large, oval, brown. Antenna long and thick, antennomeres II–XI apically circled with small granules, without setae.

Thorax. Pronotum ( Figs 5A–C , 6B ) transverse, surface smooth, disc modified with transverse crease, and sparse granules bearing short setae. Anterior margin straight, lateral margins strongly curved, all of them with dense granules bearing long setae. Posterior margin parabolic, without granules or setae. Anterior angles rounded, posterior angles acute. Mesonotum and metanotum narrower than pronotum, without modification, surface smooth, apical half of elytra darker than other parts of thorax.

Legs. Legs ( Fig. 5A ) simple, surface smooth; apex of femora with a row of small granules bearing long setae in ventral surface; apex of tibiae with a distinct spine, meso- and metatarsus obviously longer than protarsus.

Abdomen. Abdominal spiracles round. Discs of tergites I–V with dense small granules bearing short setae ( Fig. 5B , 6A & C ), granules and setae of tergite VI sparser than tergites I–V. Lateral margins of tergite I with two short projections each bearing a short seta; lateral margins of tergite II–V with three curved projections, the basal one without seta, the other two projections bearing a long seta; lateral margin of tergite VI with four curved projections, the first basal one is obviously shorter than others, basal two projections without setae, other two bearing a long seta; lateral margins of tergites VII & VIII with two curved projections each bearing a long seta; apical margins of tergites VII & VIII rounded; tergite IX posteriorly rounded with a pair of apically sclerotized urogomphi, each with three short projections bearing long setae, lateral margins with dense short projections bearing long setae. Sternites III–VI with three pairs of small projections located near apical margin, each bearing a long seta. Sternites VII and VIII with round apex, apical margin with two pairs of small projection each bearing a long seta.

Figures

FIGURE 1. Habitus of mature larva of Synchroa chinensis Nikitsky. A. Dorsal view; B. Lateral view; C. Ventral view. Scale bars: 5 mm.

FIGURE 2. Diagnostic features of mature larva of Synchroa chinensis Nikitsky. A. Head, dorsal view; B. Ditto, ventral view; C. Ditto, lateral view; D. Left mandible, dorsal view; E. Right mandible, dorsal view; F. Antenna. Scale bars: 1 mm in A–C, 0.5 mm in D–F.

FIGURE 3. Diagnostic features of mature larva of Synchroa chinensis Nikitsky. A. Labrum, dorsal view; B. ditto, ventral view; C. Ventral mouthparts, dorsal view; D. ditto, ventral view. Scale bars: 0.1 mm in A & B; 0.5 mm in C & D.

FIGURE 4. Diagnostic features of mature larva of Synchroa chinensis Nikitsky. A. Proleg, ventral view; B. Mesoleg, ventral view; C. Metaleg, ventral view; D. Abdominal segment 9, dorsal view; E. ditto, lateral view; F. ditto, ventral view. Scale bars: 0.5 mm in A–C; 1 mm in D–F.

FIGURE 5. Habitus of pupa of Synchroa chinensis Nikitsky. A. Dorsal view; B. Lateral view; C. Ventral view. Scale bars: 5 mm.

FIGURE 6. Diagnostic features of pupa of Synchroa chinensis Nikitsky. A. Abdominal segments III–VI, lateral view; B. Head and pronotum, lateral view; C. Modification of abdominal segment IV. Scale bars: 2 mm in A & B; 1 mm in C.