Psilogryllacris tchancha, Hugel, 2009

Hugel, Sylvain, 2009, Gryllacrididae and Tettigoniidae (Insecta, Orthoptera, Ensifera) from Espiritu Santo, Vanuatu, Zoosystema 31 (3), pp. 525-576 : 544-548

Psilogryllacris tchancha n. sp.

( Figs 8 ; 9 )

TYPE MATERIAL. — Vanuatu. Sanma Province, Espiritu Santo Isl., Peavot, Mt Nouresororo, 14°59’26”S, 166°45’14”E, 636 m alt., forêt de brume, sur plante de sous-bois, nuit, Exped. Santo 2006, 22.X.2006, coll. T. Robillard, ♀ holotype (TR-301, SH-035) ( MNHN- ENSIF2187).

TYPE LOCALITY. — Vanuatu, Sanma Province, Espiritu Santo Isl., Peavot, Mt Nouresororo, 14°59’26”S, 166°45’14”E, 636 m alt.

DISTRIBUTION. — Vanuatu, Sanma Province, Espiritu Santo Isl., Butmas, Tankara plateau.

ETYMOLOGY. — After Tchancha [t∫an∫a], the name given in Peavot to Gryllacridids.

HABITAT AND LIFE HISTORY TRAITS. — Not documented.

DIAGNOSIS. — Compared to other Psilogryllacris species. Body length within genus range; limbs short for the genus: FIII: 12.2 mm (12.3-13.8 mm in P. dalbertisi ( Griffini, 1909) ; similar for P. omissa Karny, 1937 [ Karny 1925, 1931]; 13.5 mm in P. rugifrons ( Karny, 1931) ; 15.4 mm in P. maculiventris ( Karny, 1931)) ; FW short: 16.4 mm (28.5-35 mm in P. dalbertisi ; similar for P. omissa [ Karny 1925, 1931]; 32.3 mm in P. rugifrons ; 34.7 mm in P. maculiventris ).

Head rounded in frontal view ( Fig. 8A ; not rounded in P. omissa , P. dalbertisi and P. rugifrons ); wider than pronotum in dorsal view (not wider than pronotum in P. omissa and P. dalbertisi ; not or inconspicuously brighter in P. rugifrons ); median ocellus inconspicuous (clearly distinct in other Psilogryllacris species ). FW not exceeding the body posterior apex (much longer in all species of the genus).

Psilogryllacris tchancha n. sp. differs from the superficially close Papuogryllacris adoxa ( Karny, 1928) by: M and Cu not fused (M and Cu fused on FW basal third); R strongly furcated (4 bifurcations in Psilogryllacris tchancha n. sp. vs. 2 in Papuogryllacris adoxa ); female SGP triangular with a minute emargination (rounded with a wide emargination in Papuogryllacris adoxa ).

MEASUREMENTS. — See Table 3.

DESCRIPTION

In addition to generic characters.Body length within the range of the genus. Head ( Fig. 8A ): rounded, oboval in frontal view, distinctly broader than the thorax; fastigium frontis distinctly wider than the scapus; face maximal width (in frontal view, below the eyes) 3 times (min: 3.5; max: 4.0; holotype: 4.0; allotype: 3.9) as wide as the fastigium frontis (measured above antennal sockets); median and lateral ocelli inconspicuous.

Thorax. Pronotum:maximal width 1.2 times wider than maximal length; anterior margin weakly convex (in dorsal view), arched (in frontal view); posterior margin almost strait, with a weak median concavity (in dorsal view), slightly arched (in posterior view); anterior sulcus deep on the lateral lobes and distinct on the discus; posterior sulcus very shallow on the discus; both sulci are converging on the lateral lobes; prozona (anterior to anterior sulcus) elevated; metazona (posterior to posterior sulcus) narrower than the anterior part of the pronotum.

Wings. FW ( Fig. 9A, B ): with 3 or 4 precostal veins; R divided in 5 or 6 veins (4 or 5 bifurcations); M contacting R at the FW base, M simple (not divided) on the right FW, divided and refused on the left FW apex; Cu simple on the left FW, divided in 3 veins (2 bifurcations); 6 A veins.

Legs. Forelegs and mid legs with the usual spurs formula (4 pairs of subapical + 1 pair of apical spurs ventrally, and one single apical spur on TII dorsally); subapical spurs distinctly reduced( Fig.8B, C ;distinctly shorter than the tibia width). Hind legs: femora 2.9 times as long as wide ( Fig. 8F ); FIII with 2 or 3 ventral inner spines; FIII with 7 or 8 spines; TIII with 5 dorsal inner spines; with 4 or 5 ventral outer spines.

SEXUAL DIMORPHISM

Male

Unknown.

Female

Sternite preceding the SGP (VII): bearing a process on the anterior margin of the sternite, directed backwards; longer than the SGP length ( Fig. 8D, E ); the base of the process is weakly sclerotized; the apex of the process is sclerotized, forms a plate with moderately converging borders, and with a triangular notch on the apex; the subgenital plate is wider than longer, triangular, with a triangular notch on the apex.

Colour

The general colour is brown, without strong black patterns, except on the fastigium. Head: face with a creamish median vertical line from the clypeus to the middle of the fastigium frontis, with poorly defined borders; clypeus cream; antennal sockets cream, eyes posteriorly surrounded by a light band; fastigium verticis borders with black lines joined on the fastigium frontis by an horizontal black line. Pronotum with indistinct pale and dark patterns. FW veins and veinlets brown, darker than the cells. HW hyaline, except the most anterior apical cells coloured as the FW cells.Legs without black patterns; hind leg with creamish and brown longitudinal patterns on the external side.

GENERIC ASSIGNATION OF P. TCHANCHA N. SP.

Karny (1937) grouped under this genus four species having in particular: long wings; particularly short ventral subapical spurs on TI and TII; the usual subapical spurs number (4 in addition to apical spurs) on TI, and usually 4 (seldom 3) spurs on TII.

Apart from its shorter wings, P. tchancha n. sp. exactly corresponds to Karny’s (1937) definition of this genus, and we therefore described it under Psilogryllacris .

Papuogryllacris Griffini, 1909 is defined in particular as having long wings too, but only 3 subapical spurs of normal size on TI and TII. Nevertheless, P. adoxa ( Karny, 1928) has distinctly reduced TI and TII subapical spurs (3 on TI and 2 on TII) and distinctly short wings and body size for the genus. For these reasons, Karny (1928) raised doubts on the affinities of P. adoxa to Papuogryllacris taxon (at this time considered as a subgenus). Interestingly, P. adoxa superficially resembles to Psilogryllacris tchancha n. sp. (size, head shape and width, short wings, short TI-TII subapical spurs, short and thick TIII, emarginated female SGP, short cerci, shape and ovipositor length). Papuogryllacris adoxa might therefore be related to Psilogryllacris tchancha n. sp., but male characters of both species and a thorough redefinition of Psilogryllacris and Papuogryllacris would be required to define whether these two species should be grouped under a new genus. Importantly, Karny (1928) described a P. adoxa variety ( var. tenuispina ) with long subapical spurs suggesting that spur length might not be stable and should be considered with caution (moreover, in some genera, given species are also displaying a spur reduction but to a lesser degree, it is the case for Nannogryllacris heurnii Karny, 1930 having reduced subapical spurs in TII).

Figures

FIG. 8. — Psilogryllacris tchancha n. sp., female holotype: A, face in frontal view; B, external view of left tibia I (note the short proximal spurs); C, posterior view of left tibia II (note the short proximal spurs); D, left side view of female terminalia; E, ventral view of female terminalia; F, lateral view of left femur III. Scale bars: A, B, C, E, 1 mm; D, F, 5 mm.

FIG. 9. — Psilogryllacris tchancha n. sp., female holotype forewing: A, left forewing; B, right forewing. Note the difference in venation. The grey dotted lines correspond to the claval fold. Scale bar: 10 mm.