Xyela curva Benson, 1938

Blank, Stephan M., Shinohara, Akihiko & Altenhofer, Ewald, 2013, <strong> The Eurasian species of <em> Xyela </ em> (Hymenoptera, Xyelidae): taxonomy, host plants and distribution </ strong>, Zootaxa 3629 (1), pp. 1-106 : 30-31

Xyela curva Benson, 1938

Xyela curva Benson, 1938: 35–36 , ♂, type locality: Austria, Weissenbach an der Tristing [= Weissenbach on river Triesting]. Xyela curvae: Zombori 1974: 238 (misspelling).

Xyela graeca: Schedl 1997 : fig. 2b (misidentification).

Description. Female. Color. Head yellow with brown and black pattern: two dark brown stripes along the frontal furrows meeting black ocellar and postocellar area and dark longitudinal spot in middle of frons always present; kidney-shaped spots on vertex usually separate from black postocellar area ( Fig. 42 ). Antennae dark brown to black, a little paler below. Thorax dorsally brown with pale pattern on pronotum, mesonotal lobes and mesoscutellum, tegulae pale, mesepisternum largely pale brown. Abdominal terga dark brown to brown, sterna often paler, lateral parts of terga 8 and 9+10 and hypopygium pale, valvifer 2 mostly dark brown, membrane between valvifer 2 and valvula 3 white, valvula 3 black or dark brown ( Fig. 92 , 118 ). Legs pale brown, posterior coxae pale, more or less their base and longitudinal ventro-lateral line dark. Wing membrane slightly infuscate, venation and pterostigma pale brown.

Morphology. Fore wing 4.7–5.2 mm long, 2.15–2.30 times longer than ovipositor sheath, vein Rs+M 150–350 µm long, 2r-m meeting Rs proximal to furcation of Rs1 and Rs2 ( Fig. 4 ). Synantennomere 3 780–930 µm long, antennomere 4 210–250 µm long and 6.5–7.5 times longer than wide distally. Article 3 of maxillary palp 530–630 µm long, 1.45–1.65 times longer than scape and about as wide as synantennomere 3. OOL: POL = 1.85–2.20: 1. Ovipositor sheath 2.05–2.30 mm long, valvula 3 1.50–1.70 times longer than valvifer 2 and 6.5–7.5 times longer than wide at basis ( Fig. 92 , 118 ). Valvula 3 of ovipositor sheath compressed in cross section, pale membranous area about as long as basal width of valvula 3, valvula 3 almost parallel-sided in basal and medial part, in distal part dorsal edge sloping down to round tip, sensilla field present and directed distad, with 7–8 setae ( Fig. 93 ). Ovipositor ( Fig. 124 ) curved downwards. Valvula 1 of ovipositor compressed, aulax terminating preapically, with preapical small tooth, ventral edge sloping up to tip, with ca 13 oblique closely spaced annuli in distal 0.2, without serrulae, olistether with 7–9 setae. Left and right valvulae 2 fused along dorsal edge up to distal 0.1. Valvula 2 with dorsal margin engraved, abruptly tapering in distal 0.1 after an inconspicious widening, darker than valvula 1, in distal half with ca 13 mostly vertical annuli, in distal 0.4 with ca 13 evenly spaced sclerotizations each enclosing 1–2 sensilla campaniformia. Posterior tibia 1.05–1.20 mm long, all claws with delicate subapical tooth.

Male. Color. Similar to female (see Fig. 43 for color pattern of head). Stripes along supraantennal furrows often smaller, antennae usually pale brown. Hypopygium and often preceding sterna pale brown.

Morphology. Fore wing 4.0– 4.6 mm long, Rs+M ca 110–200 µm long, 2r-m meeting Rs proximal to furcation of Rs1 and Rs2. Synantennomere 3 840–1,000 µm long, antennomere 4 280–350 µm long and 8.5–10.5 times longer than wide distally. Article 3 of maxillary palp 500–580 µm long, 1.35–1.55 times longer than scape and about as wide as synantennomere 3. OOL: POL = 1.65–2.00: 1. Longitudinal apodeme of basiparamere curved, basal portion in lateral position, harpe about as long as wide in lateral view ( Figs 155–156 ). Lower ergot on valvular stalk present, usually erect. Valviceps (1.60–)1.75–1.85 times longer than wide on medial lobe, lateral lamella vertical with proximal edge convex and distal base concave, proximal lobe of penis valve 0.14–0.17(–0.19) times as long as valviceps and ca 0.95–1.00 times as high as medial lobe, excision on lower edge 0.15–0.21 as deep as width of medial lobe, valviceps on medial lobe 1.00–1.20 times wider than on distal lobe, 2 distal flagella present, tip of longer flagellum reaching 1.05–1.15(–1.25) width of distal lobe ( Fig. 136 ). Valviceps without median longitudinal sclerotization, medial lobe evenly rounded, with 8–12(–19) cone-like sensilla along proximal part of upper edge and of lateral surface, upper edge between medial and distal lobe with numerous setae. Posterior tibia 1.00– 1.15 mm long, all claws with delicate subapical tooth.

Barcodes. GUID AAQ3776 (3♀).

Type material. Holotype ♀: [round label with red margin:] “Type”; “Weissenbach a. d. Tristing 5.83”; [leg.] “Kolazy”; “ Julii det. Konow”; “Holotype Xyela curva sp. nov. ♀ det. R. B. Benson 1937”; [red:] “Typus”; “ Xyela curva Benson ♀ det. S. M. Blank”. Left antenna, left middle and hind legs and ovipositor sheath missing. NMW . Paratypes: 1♀ 2♂, BMNH, NMW (other paratypes not checked) .

Host plant. Pinus cembra L. ( Liston 1995), P. mugo Turra ( Liston 1995) , Ο P. nigra ssp. laricio Poir (= P. laricio calabrica (Loud.) Cesca et Peruzzi , reported by Turrisi 2007), ● P. nigra ssp. nigra Arn. (17♀ 34♂ from 6 reared samples), ● P. nigra ssp. pallasiana Lamb. (22♀ 22♂ from 7 reared samples, 1 larva identified by barcoding), Ο P. nigra ssp. salzmannii Dunal , P. sylvestris L. ( Beneš 1975).

Biology. The flimsy, transparent cocoon was described by Schedl (1997). We have not been able to identify the mode of silk secretion unambiguously when observing X. curva larvae producing a cocoon below a pane of glass. The larvae make a cavity in the soil and cover its wall with cocoon material by repeatedly touching the surface with the stretched labio-maxillar complex and the chewing mandibles. Secretion of a liquid or a thread from the mouth or from the abdominal tip has not been observed, but possibly only a small amount of material is discharged. A histological or ultrastructural study is required to decide, whether labial glands or malpighian tubules of the larva produce the secretion during cocoon-spinning. For additional data on the biology of X. curva see Blank (2002).

Geographic distribution. Austria, Belgium ( Liston & Blank, 2006), Croatia, Czech Republic, France, Germany ( Blank & Burger 1996), Great Britain ( Liston & Blank, 2006), Greece, Hungary, Italy (for records from Sicily see Turrisi 2007), Netherlands, Slovakian Republic, Spain, Turkey ( Fig. 11 ). Benson’s (1961) record from Switzerland is a misidentication of a X. obscura female.

Remarks. Female Xyela curva are similar to X. exilicornis but have a longer ovipositor, and the pale and dark pattern of valvula 2 is more extensive. The ventral excision of the valviceps is round in X. curva but angular in other representatives of the group. In females from Austria and Germany the dark stripes along the frontal furrows are usually wider than the kidney-shaped spots, and sometimes the frontal area becomes diffuse brown, whereas in Greek and the, palest, Turkish specimens the stripes may be as small as the diameter of an ocellus and the frontal area predominantly yellow. The generally paler males exhibit a similar geographic variation of the dark pattern of the face as the females.

A complete barcoding sequence was obtained for three imagines of X. curva . The specimens display an intraspecific variation of 1.40 % and are placed at an interspecific distance of 11.29 % to the next neighbor X. alpigena ( Fig. 23 ).

The type material corresponds well with our concept of the species. Males and females have been associated by means of extensive material either reared or swept from Pinus nigra .

Imagines were reared several times from Pinus nigra ssp. nigra in Austria and Germany, and from ssp. pallasiana in Greece and Turkey. For a larva extracted from P. nigra ssp. pallasiana a short COI sequence (282 bp) could be obtained. The barcoding analysis placed this larva in the cluster of X. curva ( Fig. 23 ). Pinus nigra ssp. laricio and ssp. salzmannii are additionally supposed to be hosts due to geographical coincidence of these pine subspecies with X. curva in southern Italy and on the Iberian Peninsula (differentiation of subspecies following Barbéro et al. 1998). Beneš (1975) reported P. sylvestris . This should be deleted, because there is no indication of rearing. Liston’s (1995) records of P. cembra and P. mugo are most likely based on Benson’s (1961) misidentification of X. curva (actually X. obscura ) from 1,800 m altitude in the Swiss National Park.

Figures

FIGURE 11. Records of Xyela curva (480 specimens from 67 collection sites) and natural distribution of the host plant, Pinus nigra (solid line, combined from Meusel et al. 1965 and Barbéro et al. 1998). Additional record included for Sicily (Turrisi 2007).

FIGURE 23. Barcoding analysis of Xyela species. The tree is primarily based on specimens for which COI sequences longer than 600 bp and including less than three ambigous nucleotides could be obtained. Some shorter sequences have been added to associate sexes or larvae with imagines. Each specimen is labelled as follows: “Xyela ...”—species name; “DEIGISHym ...”—unique identification number of specimen in DEI collection; “Male / Female”—sex, larva if no sex is indicated; e.g., “661” / “603” / “658” ...—base pairs [bp] sequence length; “[0n] / [1n] / [2n]”—0–2 ambiguous nucleotides included in sequence; e.g., “Austria, Karnten [= Kärnten, Carinthia]”—country and province of origin of specimen; “BOLD: ...”—globally unique identifier (GUID). The label “Xyela 005 P. sabiniana sp.” refers to larvae obtained from Pinus sabiniana which here are identified as X. bakeri.

FIGURES 42–65. Color pattern of head of Xyela species: X. curva group, X. rasnitsyni group, X. julii group (part). Legend: HT—holotype; NT—neotype; PT—paratype.

FIGURES 86–94. Ovipositor sheath, sensilla pattern and sensilla plate (spl) at the apex of the ovipositor sheath. 86, Xyela helvetica. 87, X. longula, arrows indicate the modified hairs at apex of valvula 1. 88, X. lugdunensis. 89, X. meridionalis. 90–91, X. alpigena. 92–93, X. curva. 94, X. densiflorae.

FIGURES 105–120. Ovipositor sheaths of Xyela species. All figures at same scale. Legend: HT—holotype; NT—neotype; PT—paratype.

FIGURES 2–5. Measurements and terminology of wing venation (see explanations on pp. 8–10). 2, Xyela rasnitsyni (paratype), ovipositor sheath (embedded in glycerine and therefore valvula 3 a little wider compared to dry, pinned specimens). 3, X. alpigena, penis valve. 4, X. curva, wings. 5, X. lugdunensis (paratype of X. nigroabscondita), fore wing.

FIGURES 121–125. Distal section of ovipositors. 121, Xyela longula. 122, X. alpigena. 123, X. occidentalis (paratype). 124, X. curva. 125, X. rasnitsyni (paratype). Arrowheads in Figs 123–124 indicate preapical small tooth on dorsal edge of valvula 1.

FIGURES 146–156. Penis valves of Xyela species (X. julii group, part), and male external copulatory apparatus of Xyela in ventral and lateral view. 153–154, X. longula (penis valves removed). 155–156, X. curva (penis valves and volsellae removed). Legend: bpa—basiparamere, br—basal ring, gon—gonomacula, har—harpe, lap—lateral apodeme, vol—volsella. Figs 147, 150 and 152 reproduced from Blank et al. (2005).

FIGURES 136–145. Penis valves of Xyela species: X. curva group, X. julii group (part). Figs 138–139 and 141 reproduced from Blank et al. (2005).