Trachythorax Redtenbacher, 1908

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 : 5-7

Genus Trachythorax Redtenbacher, 1908

Trachythorax REDTENBACHER, 1908: 507 [described]. Type species: Phasma maculicollis Westwood, 1859 by subsequent designation by BROCK (1995).

Trachythorax – SHIRAKI, 1935: 78 [recorded from Taiwan]. — BRADLEY & GALLIL, 1977: 183 [higher taxonomy]. — BROCK, 1995: 93 [recorded from Malaysia, designation of type species]. — SELLICK, 1997: 116 [egg structure]. — FRITZSCHE, 1999: 80 [recorded from Thailand]. — ZOMPRO, 2004: 322 [catalogued]. — OTTE & BROCK, 2005: 336 [catalogued]. — HENNEMANN et al., 2008: 40 [recorded from China]. — CHEN & HE, 2008: 409 [key to Chinese species]. — MANDAL & YADAV, 2010: 21 [recorded from India]. — SEOW-CHOEN, 2017: 88 [recorded from Singapore]. — SEOW-CHOEN, 2018: 392 [recorded from Sumatra].

DIAGNOSIS. The genus Trachythorax differs from all other known genera of Necrosciinae by the following combination of characters:

1) Head and thorax smooth, back of head can be swollen to almost conical ( Figs 5 F–G , 10 E , 12 E , 20 C–E , 27 D , 28 D–E , 31 C ).

2) Inflatable and brightly coloured membrane between pronotum and head, usually the anterior margin of the pronotum has the same colouration ( Figs 5 F–G , 14 , 20 C–D , 24 B–C , 28 D ).

3) Females have the mesonotum at best 2× longer than the pronotum.

4) Tegmina short, not reaching median segment; alae fully developed and allowing sustained flight, anal area never brightly coloured.

5) Subgenital plate of females spoon-shaped and notched apically; not reaching apex of abdomen ( Figs 4 B–C , 13 B–C , 18 B–C , 27 F–G ).

6) Anal segment of males with two distinct hooks posteroventrally ( Figs 2 B–C , 11 B–C , 16 B– C ).

7) Poculum very short, slightly flattened, not reaching base of vomer ( Figs 2 B–C , 11 B–C , 16 B–C ).

8) Vomer distinct, elongate triangular and up-curving, ending in a single spine ( Figs 2 C , 11 C , 16 C ).

9) Strong sexual dimorphism concerning size with male distinctly smaller than the females; body length of males maximum 60% of females ( Figs 7 A–B , 11 , 21 A , 25 C–D ).

10) Posterior pole of the eggs glued to the surface of plants, sometimes with distinct specialisations on the opercular collar ( Figs 6 , 32 ).

The raised posterior portion of the mesonotum in females is a morphological character shared with the Southeast Asian Necrosciini genera Calvisia Stål, 1875 and Loxopsis Westwood, 1859 . The conical head typical for the genus Loxopsis can also be found in several representatives of Trachythorax and in Calvisia (Conocalvisia) .

SPECIES INCLUDED (15):

Trachythorax albomaculatus sp. nov.

Trachythorax auranticollis sp. nov.

Trachythorax chinensis ( Redtenbacher, 1908)

Trachythorax expallescens Redtenbacher, 1908

Trachythorax fuscocarinatus Chen & He, 1995

Trachythorax gohi Brock, 1999

Trachythorax illaesa ( Redtenbacher, 1908) stat. rev. comb. nov. Trachythorax incertus Redtenbacher, 1908

Trachythorax longialatus Cai, 1989

Trachythorax maculicollis ( Westwood, 1848)

Trachythorax planiceps Redtenbacher, 1908

Trachythorax sexpunctatus ( Shiraki, 1911)

Trachythorax sparaxes ( Westwood, 1859)

Trachythorax unicolor Redtenbacher, 1908

Trachythorax yunnanensis Gao & Liang, 2021 stat. nov.

BIOLOGY. Species were found in different biotopes, ranging from mountain evergreen rainforests to dry and severely disturbed habitats. All species are capable of good flight. Most of the time when an adult female is observed, it is accompanied by the much smaller male, and females can easily fly transporting the attached males on their backs. Males also open their wings during flight in copulation.

DISTRIBUTION. Currently known from a wide range in South-east Asia: Sri Lanka, India, Bangladesh, Myanmar, Thailand, Vietnam, Cambodia, Peninsular Malaysia, Singapore, Indonesia (Sumatra and Java), southern China (including Hainan) and Taiwan.

NOTES. The taxonomy of the genus is currently poorly resolved with several taxa, e.g. T. chinensis ( Redtenbacher, 1908) from China (Sichuan), T. expallescens Redtenbacher, 1908 from Sri Lanka, T. fuscocarinatus Chen & He, 1995 from Hainan, T. incertus Redtenbacher, 1908 from Vietnam (North Vietnam), T. longialatus Cai, 1989 from China (Sichuan) and T. unicolor Redtenbacher, 1908 from Java in need of revision and accurate re-description (see comments below), therefore a key to the species of Trachythorax is not included.

Figures

Fig. 5. Trachythorax albomaculatus sp. nov., in culture. A, mating pair, dorsal view. B, mating pair, ventral view. C, mating pair, lateral view. D, ♂, dorsal view. E. ♂, lateral view. F, ♂, head and thorax, dorsolateral view. G, ♀, head and thorax, dorsolateral view. H, ♂, ventral view. I, newly hatched nymph, dorsal view. J, subadult ♂ nymph. K, ♀ nymph.

Fig. 10. Trachythorax auranticollis sp. nov., holotype ♂ (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. 12. Trachythorax auranticollis sp. nov., paratype ♀ (RBINS). A, habitus, dorsal view. B, habitus, ventral view. C, head and thorax, dorsal view. D, habitus, lateral view. E, head and thorax, lateral view. F, head and thorax, dorsolateral view.

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. 27. Trachythorax longialatus Cai, 1989, HT ♀. A, habitus, dorsal view. B, habitus, ventral view. C, labels. D, head and thorax, dorsal view. E, terminalia, dorsal view. F, terminalia, lateral view. G, terminalia, ventral view. © NKUM.

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. 31. Trachythorax sparaxes (Westwood, 1859), South India, Tamil Nadu, 2018. © H. Sankaraman. A, mating pair, dorsal view. B, mating pair, dorsolateral view. C, ♀, head and thorax, dorsal view.

Fig. 14. Trachythorax auranticollis sp. nov., maiting pair, in Dong Nai Biosphere Reserve.

Fig. 24. Trachythorax gohi Brock, 1998 in Khao Sok N.P., Thailand. A–B, ♀, dorsal view. C, ♂, dorsal view. D, ♀ nymph. A–B, D. © C. Hübner. C. © L. Day.

Fig. 4. Trachythorax albomaculatus sp. nov., paratype ♀ (RBINS). A, terminalia, dorsal view. B, terminalia, lateral view. C, terminalia, ventral view.

Fig. 13. Trachythorax auranticollis sp. nov., paratype ♀ (RBINS). A, terminalia, dorsal view. B, terminalia, lateral view. C, terminalia, ventral view.

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

Fig. 2. Trachythorax albomaculatus sp. nov., holotype ♂ (RBINS). A, terminalia, dorsal view. B, terminalia, lateral view. C, terminalia, ventral view.

Fig. 11. Trachythorax auranticollis sp. nov., holotype ♂ (RBINS). A, terminalia, dorsal view. B, terminalia, lateral view. C, terminalia, ventral view.

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

Fig. 7. Trachythorax albomaculatus sp. nov., in Kon Chu Rang Nature Reserve. A, mating pair, dorsal view. B, mating pair, dorsolateral view. C, ♀, head and thorax, dorsolateral view. D, mating pair in habitat.

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. 25. Trachythorax illaesa (Redtenbacher, 1908) stat. rev. comb. nov. A, HT ♂, dorsal view and labels. © MNHN. B, ♂, Karnataka State, Mangalore, IX.2018. © Jitesh Pai. C–F, mating pairs. C, Matale, Laggala- Pallegama, Sri Lanka. 3.iv.2018. © Pieter Prins, iNaturalist, observations/37204645. D, Maharashtra State, Amboli, 2020. © Varad Giri. E, Karnataka State, Puttur, X.2018. © Abhijith APC. F, Karnataka State, Agumbe, X.2020. © Vishwanath Gowda.

Fig. 6. Trachythorax albomaculatus sp. nov., eggs. A–C, freshly laid eggs by wild ♀ paratype (pics by J. Constant). D–F, eggs laid by ♀ paratype (pics by B. Kneubühler). D, egg clutch. E–F, anterior view. of = opercular flap; op = operculum; lf = lateral flap; lvf = lateroventral flap.

Fig. 32. Trachythorax spp. Egg forms and parasites A–B, Trachythorax maculicollis (Westwood, 1848). A, egg clutch with parasitoid wasp, Ankor Wat, Cambodia, 24.XI.2013. © P. Bertner. B, Con Dao Island, Vietnam, 2012. © B. Kneubühler. C–F, Trachythorax illaesa (Redtenbacher, 1908) stat. rev. comb. nov. C, Agumbe, Karnataka state, X.2020. © V. Gowda. D–F, hatched eggs with parasitoid wasp, Nagla trail, Mumbai, Maharashtra state, 2018. © Prajwal Ullal. G–H, Trachythorax albomaculatus sp. nov. © B. Kneubühler.