The genus Thoradonta in Thailand (Orthoptera: Tetrigidae: Scelimeninae) with description of two new species

ABSTRACT The genus Thoradonta Hancock (Orthoptera: Tetrigidae: Scelimeninae) is newly reported from Thailand. Two new species of the genus, Thoradonta lativertexoides sp. nov. and Thoradonta spiculobaoides sp. nov., are described and illustrated with photographs and compared with similar species. A taxonomic review of the genus Thoradonta is provided and a key to all known species of the genus is given.


Introduction
The family Tetrigidae (or the superfamily Tetrigoidea: Orthoptera: Insecta) currently comprise 1828 accepted species and 83 accepted infraspecific names (some species published in 2015 are not included, http://www.gbif.org/species), and they can be found worldwide except for the polar regions.
In this study we report the genus Thoradonta Hancock as new for Thailand. Two new species, Thoradonta lativertexoides Zha and Kang sp. nov. and Thoradonta spiculobaoides Zha and Kang sp. nov., are introduced with descriptions and illustrations and compared with similar taxa. We also provide a taxonomic review of the genus Thoradonta. A key to all known species of the genus is given.

Type species
Thoradonta dentata Hancock, 1909 Generic characteristics (updated) Body size small, vertex equal to or wider than one eye, frontal ridge distinctly protruding between antennae. Antennae filiform, inserted between or below lower anterior margins of eyes. Eyes globular and prominent, lateral ocellus situated in or slightly below middle of anterior margin of eye. Distal segments of maxillary palpus slightly compressed. Pronotal disc covered with many nodules; mid-keel undulate, partially lamellate and erected before shoulders; pronotum slightly uplifted between shoulders; a pair of abbreviated carinae present between shoulders; hind process of pronotum wedgeshaped, not reaching, reaching or surpassing beyond apex of hind femur; posterior angle of lateral lobe of pronotum distinctly laminate and expanded, apex spine-like or acute dentate and extending transversely or obliquely backward, but few species truncate or subtruncate. Tegmina ovate, hindwing present or absent (Thoradonta butlini). First segment of hind tarsus generally longer than third.
Relationship to other genera The genus Thoradonta Hancock was placed in Scelimeninae (Tetrigidae) based on: (1) filiform antenna; (2) in profile frontal ridge protruding in arch-like manner between base of antennae; (3) posterior angle of lateral lobe of pronotum lamellate and expanded, apex generally spine-like.
The genus Thoradonta is closely related to the genus Criotettix Bolivar, 1887, the former differs from the latter mainly by: (1) lateral margins of pronotum behind humeral angles distinctly folded upwards; (2) partial mid-keel lamellate and erected before shoulders. Male Body size small, covered with numerous small granules and many nodules ( Figure 1A, B).
Head not protruding over level of pronotal surface; vertex about 2.0 times one eye in width, anterior margin straight, protruding forwards to same level of anterior margins of eyes, lateral margins folded upwards but not surpassing beyond top of eyes ( Figures 1B,  2B); median carina conspicuous and protruding in anterior half, which is visible before eyes in profile, while obscure or absent in posterior half; vertex and frontal ridge roundly protruding, excessively concave between lateral ocelli, and then excessively protruding in an arch-like manner between antennae, longitudinal furrow slightly wider than first segment of antenna in width (Figure 2A). Antenna filiform, 15-segmented, inserted slightly below lower margins of eyes, length of longest segment (segment IV) about six times its width. Eyes globose, protruding but not above level of pronotum ( Figure 2B); lateral ocellus situated slightly below middle of anterior margin of eye ( Figure 2A). Pronotum very coarse, covered with numerous small granules and many nodules; anterior margin straight, lateral keels erected, contracted backward, sometimes undulate in lateral view. Mid-keel not reaching anterior margin of pronotum, interrupted before shoulders, in profile upper margin distinctly undulate. These sinusoidal waves lamellate and erected, first highest, with intumesced base, both sides of intumescence with a pair of big nodules at margins of pronotum; second lamella very short and low; third lamella longest and undulate, its peak nearly of same height as first; on both sides pronotal disc distinctly concave followed by a pair of long oblique nodules, and lateral margins of pronotum distinctly folded upwards; the latter lamellae becoming lower backward and disappearing on distal part, three or four lamellae are visible and they connect with nodules of both their sides, respectively ( Figure 1A, B). Humeral angle obtuse, with a pair of abbreviated carinae between shoulders, pronotum slightly uplifted between shoulders ( Figure 1B); hind process of pronotum long cone-shaped, nearly reaching top of hind tibia, apex truncate ( Figure 1A, B); posterior angles of lateral lobes of pronotum extending outwards, distal part slightly oblique backward, fore margin of posterior angle smooth while hind margin with small teeth, apex spine-like; posterior margin of each lateral lobe with two concavities. Tegmina ovate, 2.2 times as long as wide, apex rounded. Hindwing surpassing slightly beyond top of hind process of pronotum. Upper and lower margins of fore and mid femora undulate, with fine teeth; width of basal mid femur slightly wider than width of tegmen, middle femur distinctly narrowed from basal to distal side, and basal part thicker than distal part. Hind femur about 2.6 times as long as wide, upper and lower margins dentate, outer side and upper side with a series of nodules respectively; upper margin with a triangular protrusion before antegenicular, antegenicular isolated and long triangular, its apex nearly rightangled, genicular denticle fingered extending backward and apex triangular ( Figure 2D). Width of distal hind tibia slightly wider than basal, outer side with four to six spines, inner side with four spines; first segment of hind tarsus about 1.3 times longer than third, third pulvillus longer than first and second, apices of all pulvilli sharp. Subgenital plate short cone-shaped ( Figure 2C), apex bifurcate and bidentate.
Body dark brown. Antenna brown and colour of distal segments darker; hindwings black; fore and mid femora and tibiae with three yellowish brown bands, bands of femora obscure; lower outside of hind femur black, centre of inner side of hind femur dark brown; hind tibia with two long yellowish brown bands.

Female
Unknown.

Etymology
The new species epithet is derived from Thoradonta lativertex, which means it is similar to that species.

Distribution
Thailand (Chiang Rai). Male Body size small, covered with numerous small granules and many nodules ( Figure 3A-B).
Head not protruding over level of pronotal surface; vertex 1.5-1.6 times as wide as one eye, anterior margin straight, protruding but not surpassing anterior margins of eyes,   excessively concave between lateral ocelli, and then excessively archedly protruding between antennae, longitudinal furrow about as wide as first segment of antenna ( Figure 4B). Antenna filiform, 15-segmented, inserted slightly below lower margins of eyes ( Figure 4B), length of longest segment (segment IV) about six times its width. Eyes globose, protruding but not above level of pronotum; lateral ocellus situated slightly below middle of anterior margin of eye. Pronotum very coarse, covered with numerous small granules and many nodules; anterior margin straight, lateral keels erected, slightly contracted backward, sometimes interrupted in middle or distal part excessively contracted inward ( Figure 4A). Mid-keel not reaching anterior margin of pronotum, otherwise nearly complete, in profile upper margin distinctly undulate with wave peaks becoming lower backward and disappearing in distal area. These sinusoidal waves lamellate and erected, first highest, with intumesced base, both sides of intumescence with a pair of big nodules at margins of pronotum; second lamella longest and undulate, on both sides pronotal disc distinctly concave followed by a pair of long oblique nodules, and lateral margins of pronotum distinctly folded upwards; the latter mid-keel with about seven or eight lamellae, no less than four are visible and they connect with nodules of both their sides respectively ( Figure 3A, B). Humeral angle obtusely angled, with a pair of abbreviated carinae between shoulders, pronotum slightly uplifted between shoulders ( Figure 3A, B); hind process of pronotum long cone-shaped, surpassing slightly beyond top hind femora, distal part slightly upcurved and apex truncate ( Figure 3A, B); posterior angles of lateral lobes of pronotum extending outwards, distal part nearly transverse or slightly oblique backward, fore margin of posterior angle smooth while hind margin with small teeth, apex spine-like; posterior margin of each lateral lobe with two concavities. Tegmina ovate, 2.3 times as long as its width, apex rounded ( Figure 5C). Hindwing not reaching top of hind process of pronotum but slightly surpassing beyond top of hind femur ( Figure 3A). Upper and lower margins of fore and mid femora undulate, with fine teeth; mid femur wider than tegmen and fore femur, middle femur distinctly narrowed from basal to distal side, and basal part thicker than distal part ( Figure 5A, C). Hind femur about 2.5 times as long as wide, upper and lower margins dentate, outer side and upper side with a series of nodules; upper margin with a triangular protrusion before antegenicular, antegenicular isolated and long triangular, its apex nearly right angled, genicular denticle fingered extending backward and apex nearly quadrate ( Figure 5B). Hind tibia distally slightly wider than basally, outer side with five to seven spines, inner side with for or five spines; first segment of hind tarsus 1.3-1.4 times (variable in different specimens) longer than third, third pulvillus about as long as second and slightly longer than first pulvillus, apices of all pulvilli sharp ( Figure 5D). Subgenital plate short cone-shaped, apex bifurcate and bidentate ( Figure 4D).
Body dark brown. Antenna brown and colour of distal segments darker; hindwings black; fore and mid femora and tibiae with three yellowish brown bands, bands of femora obscure; lower outside of hind femur black, centre of inner side of hind femur dark brown; hind tibia with two long yellowish brown bands.

Female
Slightly larger than male. Upper margin of fore femur arched, distinctly narrowed from basal to distal side; width of mid femur slightly narrower than width of tegmen, not narrowed or thicker from basal to distal area ( Figure 3C). Ovipositor: length of upper valvulae about 4.0 times its width, outer margins of upper and lower valvulae with small saw-like teeth ( Figure 4E). Posterior margin of subgenital plate: middle triangularly protruding, sometimes this protrusion folded inward, forming a basal concavity and a protrusion on both sides, and even the triangular protrusion invisible in ventral view ( Figure 4F).

Etymology
The new species epithet is derived from Thoradonta spiculoba, which means it is similar to that species.

Discussion
Both new species were collected in moist and stony environments near ponds in tropical rain forest of northern Thailand. Interestingly, they share striking similarities not only in some body structures, such as face, legs, male subgenital plate etc, but also with regard to their habitat. Without doubt their habitat environments have affected evolution of the shape of their bodies to a large degree. Podgornaya (1994) indicates two forms of wings (brachypterous and macropterous) as occurring in T. spiculoba specimens collected from Vietnam. Similarly we find the length of the hind process of pronotum varying distinctly in Tetrix japonica (Bolívar) (Tetriginae) specimens collected in China. Generally, some important structures, such as width of vertex, lateral lobes of pronotum and surface of pronotum, vary in different species of the genus Thoradonta. So in identifying species of the genus, we should not simply regard lengths of wings or hind process of pronotum.
Unfortunately for the genus Thoradonta, there are only three nucleotide sequences, T. yunnana (EU414829, mtDNA-COI), T. spiculoba (EU368564, mtDNA-16S) and T. nodulosa (EU414812, mtDNA-COI), submitted in NCBI databases up to now. For studying the phylogeny of the genus, apart from morphological or behavioural characters, more studies on molecular systematics need be carried out in future.

Disclosure statement
No potential conflict of interest was reported by the authors.