Trachythorax yunnanensis Gao & Liang, 2021

Bresseel, Joachim & Constant, Jérôme, 1893, Review of the Oriental stick insect genus Trachythorax Redtenbacher, 1908 with two new species from Vietnam and comments on egg parasitism and morphological counteradaptations (Phasmida, Lonchodidae, Necrosciinae), Belgian Journal of Entomology 120, pp. 1-56 : 24-33

Trachythorax yunnanensis Gao & Liang, 2021 stat. nov.

( Figs 9 , 15–22 )

Trachythorax maculicollis yunnanensis GAO & LIANG, 2021: 2 [described and figured].

MATERIAL EXAMINED. VIETNAM: (35♂♂, 23♀♀): 1♂, 1♀: Dak Nong Prov., Dray Sap. 12°29’45”N 107°54’47”E, 1–4.viii, 2019 , GTI Project, Leg. J. Constant & J. Bresseel, I.G.: 34.048 ( RBINS); 34♂♂, 22♀♀: same data, ex breeding T. Bollens 2020. (29♂♂, 17♀♀: RBINS; 5♂♂, 5♀♀: VNMN); eggs: same data , T. Bollens 2020. ( RBINS) .

LAOS: 1♂, 1♀: Province de Khammouane, rivière Hin Boun, Ban Nathan, Camp de l’Agame , Piège Malaise géant, bioqui: forêt de vallée, 17°59.733’N 104°49.395’E, 17–22.V.2012, IBCFL , Operation Canopée, radeau des cîmes, H.P. Aberlenc leg. ( RBINS) .

PHOTOGRAPHIC RECORDS. THAILAND: 1♀ ( Fig. 22 A–B ): Surat Thani prov., Ban Chalok Lam , 9°46'57"N 100°00'22"E, 9.VII.2014, A. Giudici .

LAOS: 1♂, 1♀ ( Fig. 22 C ): Luang Prabang prov., Chompet district, Ban Charn Ti, Pha Tad Ke botanical gardens, 19°53'18"N 102°07'51"E, 12.V.2020, E. Jansen .

COMMENTS. The species was originally treated as a subspecies of T. maculicollis ( Westwood 1848) by GAO & LIANG (2021), from which it was differentiated by the yellow colouration of the membrane between the pronotum and head in both sexes ( Fig. 20 C–E ) and the slightly shorter wings. Comparison of specimens ( Figs 15–18 ) and eggs ( Fig. 19 ) from Dak Nong Province in Central Vietnam matching the description provided by GAO & LIANG (2021) with ‘typical’ specimens of T. maculicollis from different localities throughout Vietnam, Cambodia and Thailand, show a distinctly more elongate anal segment in females of yunnanensis ( Fig. 18 ) when compared to T. maculicollis ( Fig. 28 F ). Furthermore, captive breeding of both ‘ yunnanensis ’ from Dak Nong Province, Vietnam ( Fig. 20 ) and of ‘typical maculicollis ’ from Phnom Aural, Cambodia ( Fig. 28 B–G ) has shown that the colour of the membrane is a stable character that does not show any variation over the generations ( BAXTER, 2002; T. Bollens, pers. comm., February 2021). Finally, considering the new records from Vietnam ( Fig. 21 ), Thailand ( Fig. 22 A–B ) and Laos ( Fig. 22 C ) available for yunnanensis , it appears that its distribution overlaps that of T. maculicollis ( Figs 9 , 29 ). Based on this data, T. yunnanensis stat. nov. is here upgraded as a valid species instead of being a subspecies of T. maculicollis . For measurements of T. yunnanensis see Table 3.

SUPPLEMENTARY DESCRIPTION.

NYMPH ( Fig. 20 F ).

Newly hatched nymphs are much similar to those of T. maculicollis ( Fig. 28 G ). Setose and predominantly grey-brown. Head with black spot between eyes and between bases of antennae; anterior portion yellowish, posterior portion grey-brown; eyes black; antennae pale. Pronotum with minute black spots anterolaterally, posteromedially and near base of fore legs. Mesopleura with minute black marking. Legs with apex of femora and tibiae black, otherwise coloured like body.

BIOLOGY ( Fig. 21 ). In Vietnam, the species was collected in tropical rainforest growing on volcanic soil, at medium altitude. Only one pair was observed in the field, at night, hanging from the leaves of a tree some 2–3 m above ground at the margin of the forest along a trail. Males and females are able to fly and the female can fly with the male attached to her back in copula.

In captivity (T. Bollens pers. comm., 2020), the species accepts Euonymus spp. ( Celastraceae ) as an alternative food plant. The females lay their egg clutches which hatch after about 2 months of incubation at 21–24°C. The nymphs of a single clutch will hatch over several days, at dawn or early morning, but not during the night, and they often do not stay on the food plants at daytime. The adult males and females show a characteristic defensive reaction when they feel disturbed or threatened: they bend the head ventrally, which reveals two membranous areas with a bright yellow to soft orange warning colour. The species also has a defensive spray which is clear and has a slightly foul smell.

DISTRIBUTION. The species is currently known from China (Yunnan Province), Laos, Thailand (Surat Thani Province) and Vietnam (Dak Nong Province) ( Fig. 9 ).

Figures

Fig. 9. Trachythorax spp. distribution map.

Fig. 15. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., ♂ (RBINS). A, habitus, dorsal view. B, habitus, ventral view. C, head and thorax, dorsal view. D, habitus, lateral view. E, head and thorax, dorsolateral view.

Fig. 16. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., ♂ (RBINS). A, terminalia, dorsal view. B, terminalia, lateral view. C, terminalia, ventral view.

Fig. 17. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., ♀ (RBINS). A, habitus, dorsal view. B, habitus, ventral view. C, head and thorax, dorsal view. D, habitus, lateral view. E, head and thorax, dorsolateral view.

Fig. 18. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., ♀ (RBINS). A, terminalia, dorsal view. B, terminalia, lateral view. C, terminalia, ventral view.

Fig. 19. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., eggs (RBINS). A, dorsal view. B, lateral view. C, anterolateral view. D, ventral view. E, anterior view. F–G, egg clutch. of = opercular flap; fr = frills.

Fig. 20. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., ex breeding. © Tim Bollens. A, ♂, dorsal view. B, ♀, dorsolateral view. C, ♂, head and thorax, dorsolateral view. D, ♂, head and thorax, dorsal view. E, ♀, head and thorax, dorsolateral view. F, newly hatched nymph.

Fig. 21. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., in situ. A, mating pair, dorsal view. B, ♀, head and thorax, dorsal view. C, ♀, lateral view. D, host plant.

Fig. 22. Trachythorax yunnanensis Gao & Liang, 2021 stat. nov., A–B, ♀ from Prov. Surat Thani. © A. Giudici. C, ♂,♀ from Luang Prabang Prov., Laos. © E. Jansen.

Fig. 28. Trachythorax maculicollis (Westwood, 1848) from Cambodia. A, mating pair, Kampot, 12.III.2009. © R. Overtoom. B–G, Kampong Speu prov, Phnom Aural, ex breeding T. Bollens. B, ♂, dorsal view. C, mating pair, lateral view. D, ♂, head and thorax, dorsal view. E, ♀, head and thorax, dorsolateral view. F, ♀ terminalia, dorsal view. G, newly hatched nymph. B–E, G. © T. Bollens. F. © J. Constant.

Fig. 29. Trachythorax maculicollis (Westwood, 1848) distribution map with data from specimens in RBINS.