Xistrella Bolívar, 1909

Xin, Lei & Deng, Weian, 2019, A new species and a new record of Xistrella from China (Orthoptera: Tetrigidae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 59 (2), pp. 453-462 : 454-457

Xistrella Bolívar, 1909

Xistrella Bolívar, 1909:400 . Type species: Xistrella dromadaria Bolívar, 1909 , by original monotypy.

Xistrella: GÜNTHER (1939: 145) ; SHISHODIA (1991: 94); BLACKITH (1992: 198); OTTE (1997: 67); JIANG & ZHENG (1998: 305); LIANG & ZHENG (1998:105); WANG (1999: 200); ZHENG (2005:131); DENG et al.(2007: 122); STOROZHENKO (2014: 47) ; DENG (2016: 119).

Redescription. General characters and coloration. Body generally moderately elongate, narrow and smooth. Colouration uniformly dark brown or yellow.

Head not exerted or exerted above pronotal surface. In dorsal view, fastigium of vertex between eyes of variable width – either 1) narrower than or 2) equal to or 3) wider than width of compound eye; anterior margin of fastigium truncate, not surpassing anterior margin of eye; median carina of vertex visible anteriorly; fossulae slightly deep or not; lateral margins of vertex slightly raised above dorsal margin of eyes as horns or not. In frontal view, frontal costa bifurcated between compound eyes, just behind paired ocelli, scutellum (longitudinal furrow) either 1) narrower than or 2) equal to or 3) slightly wider than antennal groove (AG) diameter. In lateral view, frontal ridge concave and invisible between eyes, protruding anteriorly and broadly rounded between antennal grooves; lateral (paired) ocelli located from lowest third of compound eye height to between lower margins of eyes. Antennae long, filiform, antennal grooves (AG) inserted far below or slightly below inferior margin of compound eyes. Eyes globose.

Pronotum smooth and finely granulated, in dorsal view AMP truncated, small FL1, FM; pronotal discus subulate posteriorly and extending beyond apex of hind femora; dorsum elevated behind shoulders like a hump or flat; pronotal MC of variable shape – either 1) MC of pronotum compresso-elevated, upper margin of pronotum in profile with one to two swellings anteriad of shoulders, MM1 like a hump and large, PM small (e.g. X. stylata , X. motuoensis , X. hunanensis , X. dromadaria and X. cliva ) or 2) MC of pronotum straight (e.g. X. aruna , X. dohrni and X. ophthalmica ) in profile. PML of pronotum with tegminal and ventral sinus, PML of pronotum produced outwards (e.g. X. dubia ) or turned downwards (e.g. X. dromadaria ), or obliquely truncate behind and right angled (VL). Tegmina long oval, apex round. Wings generally extending to apex of pronotal process.

Legs. Fore and middle femora slightly compressed, margins finely serrated, with carinated and straight or undulated dorsal and ventral margins. Hind femora elongate, MC finely serrated; 1stTL and 3rdTL equal in length; all pulvilli of PT1 equal in length.

Differential diagnosis. Xistrella can be easily distinguished from other genera of the subfamily Metrodorinae by a vertex not narrowly truncate in frontal view, depressed between the eyes, vertex horn drawn out or not; antennae clearly inserted below the inferior margin of eyes and considerably long; pronotum between the shoulders strongly elevated to an obtuse gibbosity or slightly elevated in the posterior part of shoulders.

Xistrella Bolívar, 1909 is morphologically similar to the genera Xistra Bolívar, 1887 and Mazarredia Bolívar, 1887 , as well as to the genera Paraphyllum Hancock, 1913 and Bermania Storozhenko, 2012 . In Xistra , the vertex horn is distinctly raised above the dorsal margin of eyes and the vertex is deeply depressed between eyes in frontal view; pronotum between the shoulders is not elevated to an obtuse gibbosity (in frontal view, the vertex horn slightly raised above the dorsal margin of eyes or not and the vertex slightly depressed or not depressed between eyes; pronotum between the shoulders generally strongly elevated to an obtuse gibbosity in Xistrella ). In Mazarredia , head is distinctly exerted above the pronotal surface; antennae short, antennal grooves inserted between the ventral margins of the compound eyes (head not exerted or a little exerted above the pronotal surface; antennae long, antennal groove inserted below the ventral margin of eye in Xistrella ). In Paraphyllum , pronotum has strongly raised median carina, usually with leaf-like depression; the anterior margin is produced over the head in profile (pronotum never evenly depressed in a leaf-like pattern, the anterior margin truncated and not produced over the posterior margin of the compound eyes in Xistrella ). In Bermania , pronotum has strongly angularly projecting FM in dorsal view; FM almost reaches the anterior edge of eyes (pronotum in dorsal view with truncated anterior margin; FM is not produced over the posterior edge of eyes).

Species composition. There are 15 species distributed in the tropics and subtropics of China, India, Indonesia (Java, Sulawesi, Sumatra), Sri Lanka, Myanmar, Nepal, Malaysia, and the Philippines ( Table 1 ) ( CIGLIANO et al. 2019).

Key to species of Xistrella Bolívar, 1909

The following identification key is based upon the keys of GÜNTHER (1939), SHISHODIA (1991), and DENG et al. (2007). Xistrella emeiensis ( Zheng, 1995) and X. guandongensis ( Liang, 1990) were described based on larvae; identity of both species is questionable and requires revision. Therefore, these two species are excluded from the identification key.

1 Pronotum slightly elevated between or behind shoulders like hump, but not compresso-elevated. ............ 2

– Pronotum flat; in profile upper margin of pronotum straight or undulate or compresso-elevated in form of hump between shoulders. ............................................ 3

2 Vertex as broad as eye; humeral angle obtusely produced; dorsum of pronotum smooth or finely granulose; pronotum slightly elevated between shoulders like hump. ............................ X. arorai Shishodia, 1991

– Vertex slightly narrower than eye; humeral angle roundly produced; dorsum of pronotum granulose and rugulose; pronotum slightly elevated behind shoulders like hump. .................................................. ...................................... X. siangensis Shishodia, 1991

3 In profile upper margin of pronotum straight (see http://orthoptera.speciesfile.org/Common/basic/ ShowImage.aspx?TaxonNameID=1101091&ImageID=151020). ................................................................... 4

– In profile upper margin of pronotum undulate ( Fig. 2C ) or compresso-elevated in form of hump between shoulders ( Figs 1 a‒d). ................................................... 8

4 Lateral margins of vertex elevated above upper margin of compound eye (see http://orthoptera.speciesfile. org/Common/basic/ShowImage.aspx?TaxonNameID=1101091&ImageID=151018); promedial conspicuous. ................................. X. aruna Ingrisch, 2001

– Lateral margins of vertex not elevated above level of upper margin of compound eye (see http://orthoptera. speciesfile.org/Common/basic/ShowImage.aspx?TaxonNameID=1101084&ImageID=213619); promedial inconspicuous. ............................................................... 5

5 Midfemur wider than tegmina, lower margins of middle femora undulate. ................................................ ..................................... X. javanensis ( Günther, 1937)

– Midfemur narrower than or equal in width to tegmina, lower margins of middle femora straight. .............. ........................................................................................ 6

6 Width of vertex equal to width of eye;width of scutellum narrower than diameter of antennal grooves (see http://orthoptera.speciesfile.org/Common/basic/ ShowImage.aspx?TaxonNameID=1101085&ImageID=230732). ............. X. ophthalmica ( Bolívar, 1909)

– Width of vertex narrower than width of eye; width of scutellum equal to diameter of antennal grooves (see http://orthoptera.speciesfile.org/Common/basic/ ShowImage.aspx?TaxonNameID=1101089&ImageID=230688). ................................................................... 7

7 Lateral margins of vertex reaching upper margin of eye; hind wings reaching apex of pronotal process. .... ......................... X. dohrni palawanica Günther, 1939

– Lateral margins of vertex reaching middle of eye; hind wings far surpassing apex of pronotal process. ............ ................................. X. dohrni dohrni Günther, 1939

8 In profile upper margin of pronotum undulate. ....... 9

– In profile upper margin of pronotum compresso-elevated in form of a hump between shoulders. ......... 10

9 Upper margin of pronotum before shoulders with two swellings and undulate in profile, promedial and first metamedial are connected ( Fig. 2C ); antennae inserted far below inferior margin of eye ( Figs 2C,H ); lower margins of middle femora undulate. ............................. .................. X. dubia ( Brunner von Wattenwyl, 1893)

– Upper margins of pronotum each with hump before shoulders and hind shoulders in profile, promedial and first metamedial are not connected ( Fig. 4B ); antennae inserted slightly below inferior margin of eye ( Fig. 4C ); lower margins of middle femora straight. ....................... ...................................... X. hainanensis Deng sp. nov.

10 Lateral margins of vertex slightly elevated above upper margin of compound eye; lower margins of fore and middle femora undulate. .. X. stylata ( Hancock, 1907)

– Lateral margins of vertex not elevated above level of upper margin of compound eye; lower margins of fore and middle femora straight. ...................................... 11

11 Vertex narrower than eye; median carina of pronotum compresso-elevated in form of triangular hump between shoulders ( Figs 1 a‒b). ..................................... 12

– Vertex as broad as eye; median carina of pronotum compresso-elevated in form of arched hump between shoulders ( Figs 1 c‒d). ................................................ 13

12 VL right angle; width of basal part of hump equal to length of tegmina in profile. ............................................ ............................................ X. motuoensis ( Yin, 1984)

– VL obtuse-rounded; width of basal part of hump bigger than length of tegmina in profile. ............................ ........................................... X. hunanensis Wang, 1999

13 Height of pronotal hump (first metamedial) smaller than width of tegmina; upper margin of pronotum between shoulders slightly arched elevated in profile. .... .......................................... X. wuyishana Zheng, 1991

– Height of pronotal hump (first metamedial) larger than or equal to width of tegmina; upper margin of pronotum between shoulders distinctly elevated in form of hump in profile. ............................................ 14

14 PM not distinct; height of pronotal hump (first metamedial) equal to width of tegmina. ................................ ....................................... X. dromadaria Bolívar, 1909

‒ PM distinct; height of pronotal hump (first metamedial) larger than width of tegmina. ..................................... ....................................................... X. cliva Zheng, 1991

Figures

Fig. 2. Xistrella dubia (Brunner von Wattenwyl, 1893).A – body of male, dorsal view; B – body of female, dorsal view; C – body of male, lateral view; D – body of female, lateral view; E – right antenna; F – head, dorsal view; G – head, frontal view; H – head and pronotum, lateral view; I – left fore femur, lateral view; J – left middle femur, lateral view; K – left hind femur, lateral view; L – left hind tibia, dorsal view; M – left posterior tarsi, lateral view. Scale bar = 1 mm.

Fig. 1. Morphology of Xistrella species. a – X. motuoensis Yin, 1984, body, lateral view; b – X. hunanensis Wang, 1999, body, lateral view; c – X. wuyishana Liang, 1991, body, lateral view; d – X. cliva Liang, 1991, body, lateral view.Drawings according to: a –YIN (1984); b – WANG (1999); c, d – ZHENG (1991).

Fig. 4. Xistrella hainanensis Deng, sp. nov., female, holotype: A – body, dorsal view; B – body, lateral view; C – head and pronotum, lateral view; D – head, frontal view; E – head, dorsal view; F – head, lateral view; G – right antenna; H – left fore femur, lateral view; I – left middle femur, lateral view; J – left hind femur, lateral view; K – left posterior tarsi, lateral view; L – subgenital plate, ventral view. Scale bar = 1 mm