Description of four new species of the subgenus Tachycines (Gymnaeta) Adelung, 1902 (Orthoptera: Rhaphidophoridae) from caves in China and additional notes on some previously known species

In this paper, four new cave-dwelling species of the subgenus Tachycines (Gymnaeta) from Guangxi, Hunan and Jiangxi are described, i.e., Tachycines (Gymnaeta) quadratus sp. nov., Tachycines (Gymnaeta) shiziensis sp. nov., Tachycines (Gymnaeta) sparsispinus sp. nov. and Tachycines (Gymnaeta) papilious sp. nov. The female of Tachycines (Gymnaeta) liboensis Zhu, Chen & Shi, 2020 is recorded for the first time. Moreover, images illustrating the morphology of the four new and three previously described species are provided.

This paper describes four new species from caves in Guangxi, Hunan and Jiangxi. Images showing the morphology of the four new and three previously described species are provided.

Material and methods
Specimens were preserved in 75% ethanol and measured by Vernier caliper. Morphological structures were examined using a Leica M205A stereo microscope and a Leica DFC450 digital imaging system was used to acquire morphological images. The photos were edited with Adobe Photoshop CC 2018. Type specimens are kept at the Museum of Hebei University, Baoding, China (HBU).
The following conventions were adopted for the specimen measurements: body length from apex of fastigium verticis to posterior margin of the last abdominal tergite; pronotum length from anterior margin of pronotum to posterior margin along midline; fore femur length from base of fore femur to apex of genicular lobe; hind femur length from base of hind femur to apex of genicular lobe; hind tibia length from base of hind tibia to apex; hind basitarsus length from base of hind basitarsus to apex; ovipositor length from base of subgenital plate to apex of ovipositor.  Adelung, 1902 Tachycines (Gymnaeta) quadratus sp. nov. urn:lsid:zoobank.org:act:A76373AC-5FF4-4ED9-8496-A4180B9D1456 Figs 1, 8A-B

Diagnosis
The new species is similar to Tachycines (Gymnaeta) sonlaensis Gorochov, 1990 with regard to the dorsal sclerite of the male genitalia, but differs from the latter by: projection of fastigium verticis is fully reduced; hind tibia has a lower number of dorsal spines (only 11-13 inner spines and 10-14 outer spines instead of 30-40 spines in T. (G.) sonlaensis); interno-dorsal spine is distinctly shorter than hind basitarsus instead of nearly equal in length to hind basitarsus in T. (G.) sonlaensis.

Etymology
The name of the new species derives from the Latin word 'quadratus' referring to the dorsal sclerite of the male genitalia quadrate being quadrangular.
THorax. Pronotum long, anterior margin straight, posterior margin arcuate; lateral lobes longer than high, ventral margin arc-shaped. Mesonotum and metanotum short, posterior margin of mesonotum arcuate, posterior margin of metanotum straight. Legs. Fore coxa with one small spine; femur unarmed on ventral surface, internal genicular lobe with one small spine, external genicular lobe with one long spine; tibia with one inner spine and one to two outer spines on ventral surface, apex with one pair of ventral spines, between paired ventral spines with one small spine. Mid femur unarmed on ventral surface, internal and external genicular lobes with one long spine each; tibia with only one outer spine on ventral surface, apex with one inner spine on dorsal surface and one pair of ventral spines, between paired ventral spines with one small spine. Hind femur unarmed on ventral surface, internal and external genicular lobes unarmed; tibia with 11-13 inner spines and 10-14 outer spines on dorsal surface, arranged sparsely, with one pair of dorsal spines in subapical area, and at apex with one pair of dorsal spines and two pairs of ventral spines, interno-dorsal spine distinctly shorter than hind basitarsus. Hind basitarsus unarmed on dorsal surface, ventral surface with bristles.
MaLe aBdoMen. Posterior margins of all abdominal tergites relatively straight, abdominal sterna with conical tubercles. Epiproct tongue-shaped, paraproct simple, nearly triangular in lateral view. Cercus slender, conical, apex acute. Genitalia with six membranous lobes, apical area of dorso-median lobe with one pair of small lobes, lateral sclerite indistinct, dorso-lateral lobes nearly equal in length to dorsomedian lobe, ventro-lateral lobes nearly equal in length to dorso-lateral lobes, ventro-median lobe short; dorsal sclerite quadrate. Subgenital plate quadrangular, transverse and broad, middle area with conical tubercle, posterior margin straight.
FeMaLe aBdoMen. Ovipositor longer than half the length of hind femur, slightly curved upward, dorsal margin smooth, apical area of ventral margin denticulate. Subgenital plate nearly triangular, both sides of basal area with one triangulate lobe, apex acute.

Diagnosis
The new species is similar to other congeneric species in appearance, but it can easily be distinguished by the shape of the dorsal sclerite of the male genitalia, the dorsal sclerite being trapezoidal, the basal part narrow, with one deep concavity, and the posterior margin being broad and slightly concave.

Etymology
The name of the new species refers to the type locality.

Description Male
Body. Slightly smaller than in other congeneric species.
Legs. Fore coxa with one small spine; femur unarmed on ventral surface, internal genicular lobe unarmed, external genicular lobe with one long spine; tibia with only two outer spines on ventral surface, apex with one pair of ventral spines, between paired ventral spines with one small spine. Mid femur unarmed on ventral surface, internal and external genicular lobes with one long spine each; tibia unarmed on ventral surface, apex with one pair of ventral spines, between paired ventral spines with one small spine. Hind femur unarmed on ventral surface, internal and external genicular lobes unarmed; tibia with 23-24 inner spines and 21-24 outer spines on dorsal surface, with one pair of dorsal spines in subapical area, and at apex with one pair of dorsal spines and two pairs of ventral spines, interno-dorsal spine slightly shorter than hind basitarsus. Hind basitarsus with one apical spine on dorsal surface, ventral surface with bristles.
MaLe aBdoMen. Posterior margins of all abdominal tergites relatively straight, abdominal sterna without obvious conical tubercles. Epiproct tongue-shaped, paraproct simple, nearly triangular in lateral view. Cercus extremely long, conical, apex acute. Genitalia with six membranous lobes, apical area of dorso- median lobe with one pair of small lobes, lateral sclerite slender, reaching subapex of dorso-median lobe, dorso-lateral lobes slightly longer than dorso-median lobe, ventro-lateral lobes much shorter than dorso-lateral lobes, ventro-median lobe short; dorsal sclerite trapezoidal, basal part narrow, with one deep concavity, posterior margin broad and slightly concave. Subgenital plate quadrangular, posterior margin slightly concave.

Female
Unknown.

Etymology
The name of the new species is formed from the Latin words 'sparsus' ('scattered') and 'spina' ('spine'), referring to the low number of dorsal spines on the hind tibia. Paratypes CHINA • 2 ♂♂, 1 ♀; same collection data as for holotype; HBU.
Legs. Fore coxa with one small spine; femur unarmed on ventral surface, internal genicular lobe unarmed, external genicular lobe with one long spine; tibia with one inner spine and two outer spines on ventral surface, apex with one pair of ventral spines, between paired ventral spines with one small spine. Mid femur unarmed on ventral surface, internal and external genicular lobes with one long spine each; tibia with one inner spine and one to two outer spines on ventral surface, apex with one pair of dorsal spines and one pair of ventral spines, between paired ventral spines with one small spine. Hind femur unarmed on ventral surface, internal and external genicular lobes unarmed; tibia with six to eight inner and outer spines on dorsal surface each, subapical area unarmed, and at apex with one pair of dorsal spines and two pairs of ventral spines, interno-dorsal spine distinctly shorter than hind basitarsus. Hind basitarsus unarmed on dorsal surface, ventral surface with bristles. MaLe aBdoMen. Posterior margins of all abdominal tergites relatively straight, abdominal sterna without obviously conical tubercles. Epiproct tongue-shaped, paraproct simple, nearly triangular in lateral view. Cercus slender, conical, apex acute. Genitalia with six membranous lobes, apical area of dorso-median lobe with one pair of small lobes, lateral sclerite short, basal area broad, gradually narrowing to apex, dorso-lateral lobes nearly equal in length to dorso-median lobe, ventro-lateral lobes nearly equal in length to dorso-lateral lobes, ventro-median lobe short; basal margin of dorsal sclerite narrow, truncate, posterior margin with one broad concavity. Subgenital plate quadrangular, posterior margin relatively straight.
FeMaLe aBdoMen. Ovipositor longer than half the length of hind femur, slightly curved upward, dorsal margin smooth, apical area of ventral margin denticulate. Subgenital plate nearly triangular, both sides of basal area with one triangulate lobe, apex blunt.

Description Male
Body. Medium-sized.
Legs. Fore coxa with one small spine; femur unarmed on ventral surface, internal genicular lobe with one small spine, external genicular lobe with one long spine; tibia with one inner spine and two outer spines on ventral surface, apex with one outer spine on dorsal surface and one pair of ventral spines, between paired ventral spines with one small spine. Mid femur unarmed on ventral surface, internal and external genicular lobes with one long spine each; tibia with one inner spine and one outer spine on ventral surface, apex with one pair of dorsal spines and one pair of ventral spines, between paired ventral spines with one small spine. Hind femur unarmed on ventral surface, internal genicular lobe with one spine, external genicular lobe unarmed; tibia with 104 inner spines and 114 outer spines on dorsal surface, with one pair of dorsal spines in subapical area, and at apex with one pair of dorsal spines and two pairs of ventral spines, interno-dorsal spine markedly shorter than hind basitarsus. Hind basitarsus with one apical spine on dorsal surface, ventral surface without bristles.
MaLe aBdoMen. Posterior margins of all abdominal tergites relatively straight, abdominal sterna with distinct conical tubercles. Epiproct semicircular, paraproct simple, nearly triangular in lateral view. Cercus extremely long, conical, apex acute. Genitalia with six membranous lobes, basal area of dorsomedian lobe forming a protuberance, apical area with one pair of small lobes, lateral sclerite narrow, crescent shaped, dorso-lateral lobes slightly longer than dorso-median lobe, ventro-lateral lobes shorter CoLoraTion. Body uniformly yellowish-brown. Eyes black.

Female
Unknown.

Descriptive notes of the female
Ovipositor nearly equal in length to half the length of hind femur, slightly curved upward, dorsal margin smooth, apical area of ventral margin denticulate. Subgenital plate nearly triangular, both sides of basal area with one triangular lobe, apex blunt.

Remarks
The female of this species is recorded and described here for the first time. (Rampini & Di Russo, 2008) Figs 6, 8I-J

Discussion
Gymnaeta was erected as a genus by Adelung (1902). Karny (1934) considered it as a subgenus of Tachycines. Gorochov & Storozhenko (1992) compared the genus Diestrammena with the genus Tachycines and thought that the structure of their male genitalia was very similar. The most remarkable difference between them was the number of spines on the hind tibia, which was unstable in this subfamily. Therefore, Gorochov & Storozhenko (1992) insisted that the number of spines on the hind tibia is completely inappropriate to be used to differentiate genera and transferred the subgenus Gymnaeta to the genus Diestrammena. Moreover, according to the minor differences in the structures of male genitalia, the subgenus Tachycines may also have to be placed in the genus Diestrammena. However, Qin et al. (2018) followed Karny's classification system and supposed that the arrangement of spines on the hind tibia could be used to identify not only the two genera but also other genera in Aemodogryllini. Therefore, they reinstated the status of the genus Tachycines and retransferred the subgenera Gymnaeta and Tachycines from the genus Diestrammena to the genus Tachycines (Qin et al. 2018). At present, species belonging to the subgenus Gymnaeta can easily be identified according to the male genitalia and the absence of spines on the hind femora. The most controversial question is whether the spines on the hind tibia could be used as a generic character to classify Diestrammena and Tachycines. In the absence of sufficient evidence to clarify this issue, no changes have been made to the current classification system and the species are temporarily placed in the genus Tachycines. More evidence is needed for further study.
The South China Karst is one of the world's biodiversity hotspots with an abundant diversity of species (Shu et al. 2013;Monro et al. 2018). Up to now, approximately 145 species of Rhaphidophoridae are recorded from China, among which only 25 species are described from caves.
Cave crickets have developed some characteristics to adapt to cave life, such as a light body color, different degrees of degenerated eyes and fastigium verticis, longer appendages, etc. This fauna represents a good model to study biogeographical issues (Weckstein et al. 2016), and especially to discuss the current distribution pattern of cave species in relation to the geology and the geomorphology, as well as to analyze the relationships between epigean and subterranean species.
However, habitats of cave systems are easily destroyed and cannot be recovered and many undescribed species are in danger of extinction (Jaffé et al. 2016;Borges et al. 2019).