Necremnus metalarus, (WALKER)

Gebiola, Marco, Bernardo, Umberto, Ribes, Antoni & Gibson, Gary A. P., 2015, An integrative study of Necremnus Thomson (Hymenoptera: Eulophidae) associated with invasive pests in Europe and North America: taxonomic and ecological implications, Zoological Journal of the Linnean Society 173 (2), pp. 352-423 : 375-378

publication ID	https://doi.org/ 10.1111/zoj.12210
persistent identifier	https://treatment.plazi.org/id/293AD62E-FF87-3439-10EC-FAE6FDD9FCE8
treatment provided by	Felipe
scientific name	Necremnus metalarus
status

Treatment

NECREMNUS METALARUS (WALKER) View in CoL ( FIGS 26–39 View Figures 26–31 View Figures 32–39 )

Eulophus Metalarus Walker, 1839: 187–188 View in CoL . ♀ lectotype (BMNH, here designated).

Type material

Walker (1839) described Eulophus metalarus based on at least seven females and males, the description also including six varieties, collected from the Isle of Wight, and Holywood, near Belfast, Northern Ireland. The BMNH has at least two females indicated to form part of the type series. Two are point-mounted and have a rectangular card below the point to help protect the specimen. One has the following four labels: (1) a circular, purple-bordered label with ‘LECTOTYPE’; (2) a rectangular, handwritten label with ‘ Eulophus metalarus Walker’ handwritten on one side and ‘Stood under this name in old B.M. Coll. C. Waterhouse’ printed on the other side; (3) a rectangular label with ‘ Eulophus metalarus Walker LECTOTYPE: ♀ M. de V. Graham det. 1958’ partly printed and handwritten; and (4) a square label with ‘B.M. TYPE HYM. 5.2506’. This female is complete ( Figs 26, 27 View Figures 26–31 ) although the head is collapsed and covered with a white substance that obscures the sculpture ( Fig. 30 View Figures 26–31 ). The other has a circular, blue-bordered label with ‘PARALECTOTYPE’ and the same double-sided label as the specimen labelled as the lectotype. Head sculpture is visible in this female, but it lacks the apical funicular and clava of the left antenna and has the left fore wing torn and curled at the level of the stigmal vein. Both females are typical for the species in having a single infuscate region behind the stigmal vein ( Fig. 29 View Figures 26–31 ), the tegulae dark brown apically but more translucent yellowish basally ( Fig. 28 View Figures 26–31 ), and the dorsellum and propodeum quite strongly reticulate ( Fig. 31 View Figures 26–31 ). In order to stabilize the concept of the name we designate the best-preserved female, the one with Graham’s lectotype label, as the lectotype of E. metalarus , and the one with his paralectotype label as the paralectotype.

The general collection contains another similar pointmounted female with the same double-sided label as the other two specimens, a circular label with ‘38/ 7\12/65’ on three separate lines, and a small rectangular label with ‘Clermont’. This female is not part of the original type series because it is from Clermont , France ( Walker, 1846a) .

Redescription

Female

Body length 1.8–3.3 mm. Head and mesosoma dark green, coppery lustre dorsally ( Figs 34, 35 View Figures 32–39 ). Antenna ( Fig. 38 View Figures 32–39 ) with scape dark, pedicel and flagellum dark brown. Tegula partly or rarely entirely yellow, usually dark brown apically and lighter, translucent yellowish basally ( Fig. 28 View Figures 26–31 ). Legs ( Figs 27 View Figures 26–31 , 32 View Figures 32–39 ) with meso- and metatibiae almost entirely dark although usually narrowly pale basally, the paler region typically somewhat broader ventrally than dorsally so as not to be distinctly and uniformly differentiated. Hind leg with tarsus sometimes entirely brown, but usually basal tarsomere white to yellowish-brown at least basally and apical three tarsomeres brown or increasingly dark brown. Fore wing usually with at least faint brownish infuscation behind stigmal vein extending at most half width of wing ( Fig. 29 View Figures 26–31 ), although sometimes completely hyaline ( Fig. 36 View Figures 32–39 ) or rarely with broad, faint brownish region behind marginal vein basally, posteriorly the latter region extended obliquely to merge with brownish region behind stigmal vein to form broadly U-shaped infuscate region. Gaster dark brown.

Head in dorsal view ( Fig. 34 View Figures 32–39 ) 1.1–1.2 × as broad as mesoscutum and 2.2–2.5 × as broad as long; in frontal view ( Fig. 30 View Figures 26–31 ) transverse-oval, 1.2–1.35 × wider than high; temple 0.12–0.2 × as long as eye length. POL 1.8– 2 × OOL, OOL 1.85–2.15 × OD. Eyes 1.3–1.5 × as high as broad, separated by 0.9–1.1 × their height, with very short, sparse hairs. Gena straight to weakly convex, strongly converging, malar space 0.37–0.42 × height of eye. Mouth opening 1.4–1.5 × as broad as malar space. Frons flattened on sides, weakly reticulate, with very short hairs, without piliferous punctures.

Antennae ( Figs 30 View Figures 26–31 , 38 View Figures 32–39 ) inserted with ventral margins of toruli at level of ventral margins of eyes. Scape 5.5– 6.5 × as long as broad, 0.73–0.9 × as long as height of eye, not reaching median ocellus. Pedicel + flagellum 1.1–1.25 × as long as breadth of head ( Fig. 30 View Figures 26–31 ) and 1.25–1.35 × as long as breadth of mesoscutum. Pedicel in profile 1.8–2.15 × as long as broad. Funicle with two anelli and three funicular segments, funicular segments decreasing in length, funicle proximally slightly (1.1–1.3 ×) stouter than pedicel, distally very slightly thickening (F3 1.1–1.35 × as broad as F1) and slightly compressed; F1 distinctly longer (1.7–2.15 ×) than pedicel; F1 + anelli 1.8–2.3 × as long as pedicel; F1– F3 3–3.4, 2–2.65, and 1.65–2.15 × as long as broad, respectively. Clava three-segmented, acute apically, slightly (1.05–1.1 ×) broader than F3, 2.6–3.15 × as long as broad, and 0.8 × as long as F2 + F3; clava with C1 1–1.4 × as long as broad and 0.4–0.45 × length of clava. Flagellum with sensilla placed in three or rarely four irregular rows on F1, in two or rarely three irregular rows on F2 and F3, and in two rows on C1; with short, dense, decumbent setae.

Mesosoma in dorsal view ( Figs 34, 35 View Figures 32–39 ) 1.6–1.9 × as long as broad, in lateral view ( Fig. 32 View Figures 32–39 ) 1.9–2.15 × as long as high with propodeum sloping at about 40– 45° with respect to plane of mesoscutum and scutellum. Pronotum 0.2–0.3 × as long as mesoscutum. Mesoscutum transverse, 1.5–1.75 × as broad as long, and 1–1.27 × as long as scutellum; with slightly raised, moderately strong reticulation, the reticulations isodiametric. Scutellum convex, 1–1.15 × as long as broad, sculpture of scutellum and axillae finer and not as strong as mesoscutum. Dorsellum ( Figs 35, 37 View Figures 32–39 ) usually quite strongly mesh-like reticulate. Propodeum ( Figs 35, 37 View Figures 32–39 ) medially 1.35–1.7 × as long as dorsellum and 0.4–0.5 × as long as scutellum; typically comparatively strongly sculptured, quite distinctly mesh-like reticulate except sometimes in smaller individuals, with distinct median carina over most of length; without or with variably distinct oblique angulation or carinate plica partly between spiracle and foramen; callus with long, white setae; spiracles obliquely oval, separated from metanotum by 0.3–0.5 × smallest diameter.

Fore wing ( Fig. 36 View Figures 32–39 ) 2.35–2.6 × as long as broad. Costal cell 0.95–1.1 × as long as marginal vein; ventrally with a complete row of setae and some sparse setae apically, and dorsally with a short row of six to eight setae apically. Submarginal vein dorsally with 13–20 setae. Marginal vein 2.8–3.4 × as long as stigmal vein. Stigmal vein moderately thin basally; stigma elongate, hardly thickened. Postmarginal vein 1.25–1.5 × as long as stigmal vein and 0.3–0.47 × as long as marginal vein. Basal fold pilose; basal cell open posteriorly, dorsally bare and ventrally with variable number of minute setae near submarginal vein. Speculum broad, closed posteriorly. Fore wing with moderately dense, dark pilosity beyond the speculum; marginal fringe short. Hind wing rounded at apex.

Gaster ( Fig. 34 View Figures 32–39 ) ovate, 1.9–2.3 × as long as broad, 1.1–1.3 × as long as mesosoma, 0.85–1.05 × as long as head plus mesosoma, and 0.93–1 × as broad as mesosoma; acute apically with syntergum transverse, 0.4–0.55 × as long as broad. Ovipositor slightly protruding. Hypopygium reaching 0.33–0.45 × length of gaster. Other features not detailed in description as in N. artynes .

Male ( Fig. 27 View Figures 26–31 )

Similar to female except in structure of antennae and gaster, and hyaline wings. Antenna ( Fig. 39 View Figures 32–39 ) with flagellar rami long, with long, hair-like setae and with mps. Fore wing hyaline. Tegula variably distinctly and extensively yellow basally to entirely yellow. Legs ( Fig. 27 View Figures 26–31 ) with similar colour pattern as female or up to about basal half of meso- and metatibiae pale. Metanotum with dorsellum shallowly mesh-like reticulate to meshlike coriaceous. Propodeum mesh-like coriaceous or at most sculpture defined by very weakly raised lines; spiracle slightly separated from metanotum.

Distribution

Europe, and introduced in North America ( Noyes, 2013). We sequenced specimens from France and Italy, the latter a new country record.

Hosts

Coleophora laricella (Hübner) ( Lepidoptera : Coleophoridae ) on Larix europaea Philip Miller (Pinaceae) based on sequenced specimens. Noyes (2013) recorded Col. laricella as well as Coleophora pennella (Denis & Schiffermüller) [= Coleophora onosmella (Brahm) ] plus other species in Gelechiidae , Gracillariidae , Lyonetiidae , and Yponomeutidae and plant associates in nine families. Confirmed host records based on examined specimens in the BMNH are Argyresthia thuiella (Packard) (Yponomeutidae) , Leucoptera (= Lithocolletis ) spartifoliella (Hübner) ( Lyonetiidae ), and Phyllonorycter scopariella (Zeller) (Gelechiidae) . Other confirmed host records based on specimens in R. R. Askew’s collection are Coleophora serratella (L.) on Betula , Coleophora vitisella Gregson on Vaccinium vitis-idaea L., Phyllonorycter quinqueguttella (Stainton) on Salix repens L., and Mompha miscella (Denis & Schiffermüller) (Momphidae) on Helianthemum sp. (Cistaceae) .

Discussion

We sequenced only two individuals that we identified as N. metalarus ( NM 63 and NM151), insufficient to form a proper morphological species concept. Nonetheless, within the N. artynes group, typical females of N. metalarus are uniquely distinguished by having a comparatively coarsely sculptured, reticulate dorsellum and propodeum ( Figs 35, 37 View Figures 32–39 ) in combination with almost entirely dark metatibia ( Figs 27 View Figures 26–31 , 32 View Figures 32–39 ). Owing to their metatibial colour pattern, broad speculum, and propodeal spiracles separated slightly from the metanotum, females, particularly those with entirely hyaline fore wings, could be mistaken for those of N. leucarthros . However, females of N. leucarthros have a dark brown tegula, whereas in N. metalarus the tegula is usually yellowish to variably distinctly bicoloured, brown apically and more translucent yellowish basally ( Fig. 28 View Figures 26–31 ). There is also typically a subtle colour difference between the metatibia of females of the two species. In N. leucarthros females, not only is the basal yellow region very short, but it usually is also quite abruptly and uniformly delineated ( Figs 145, 146 View Figures 145–150 ). Necremnus metalarus females typically have the pale and dark coloration merging more gradually and the basal pale region somewhat longer ventrally than dorsally ( Figs 27 View Figures 26–31 , 32 View Figures 32–39 ) so as not to be as abruptly delineated as in N. leucarthros . Typical N. leucarthros females also have a shorter F1 ( Fig. 149 View Figures 145–150 ) and a more finely sculptured, mesh-like coriaceous to coriaceous-imbricate propodeum ( Figs 143 View Figures 139–144 , 147 View Figures 145–150 ). However, although most female N. metalarus we have seen have F1 about twice the length of the pedicel ( Fig. 38 View Figures 32–39 ), females at the lower end of the size variation can have F1 only about 1.8 × or slightly less than the length of the pedicel, similar to some N. leucarthros , as well as a comparatively finely sculptured metanotum and propodeum. This is true for four poorly preserved BMNH females from England associated with several males reared from Col. laricella . Males associated with females from this rearing have a similar metatibial colour pattern as females, whereas males associated with females that we identify as N. metalarus from other rearings have the metatibia much more broadly pale basally, similar to N. artynes males. Most female N. metalarus also have the tegula yellowish or noticeably bicoloured, being darker brown apically and lighter and more translucent yellowish to yellowish brown basally ( Fig. 28 View Figures 26–31 ).