Mesopolobus melitensis Askew, 2014

Dorchin, Netta, Mifsud, David & Askew, Richard, 2014, Saltbush-associated Asphondylia species (Diptera: Cecidomyiidae) in the Mediterranean Basin and their chalcidoid parasitoids (Hymenoptera: Chalcidoidea), Zootaxa 3869 (4), pp. 383-396 : 391-394

Mesopolobus melitensis Askew , n. sp.

(Chalcidoidea: Pteromalidae )

Female ( Fig. 19 ). Length 1.7–2.3 mm. Head and thorax purplish black; propodeum dark blue-green, shiny; gaster dark brown dorsally, the first tergite bluish-green and the sixth with weak greenish reflections, laterally with mainly coppery tints. Antenna with scape and pedicel light brown, funicle segments except the fifth darker brown, clava pale yellow. Legs with coxae dark brown, weakly metallic, colored as thoracic pleura; legs otherwise light brown, the pro- and mesofemora often, and tibiae sometimes, slightly darker; apical tarsal segments and pretarsi dark brown. Wings clear, venation pale testaceous.

Head ( Fig. 21 ): 1.3 times breadth of thorax, in dorsal view 2.3 times as broad as long, frons slightly protuberant with scrobal depression hardly developed, occiput strongly emarginate, temples about one-seventh of eye length; head in facial view 1.3 times as broad as high. Ocelli small, in a triangle of about 120°, POL twice OOL, OOL rather more than 3 times ocellar diameter. Antennal toruli with upper margins at about lower orbital level. Clypeus with anterior margin very weakly emarginate, striate, striae not extending onto face; face and gena finely and uniformly reticulate. Oral fossa 1.6 times malar space. Left mandible with 3 teeth, right with 4. Antennal scape about equal in length to height of eye, reaching only to about one diameter below anterior ocellus; pedicel plus flagellum 0.8 times as long as breadth of head; pedicel in dorsal view almost 3 times as long as broad, almost as long as the first four flagellar segments; 3 anelli, first two transverse, third subquadrate; first four funicle segments subquadrate, fifth weakly transverse, first funicle segment broader than pedicel; clava a little shorter than three preceding funicle segments, not quite 3 times as long as broad, apex bluntly rounded; sensillae on funicle and claval segments rather sparse, in single transverse row on each segment.

Mesosoma 1.2 times as long as broad; pronotum with collar almost one-quarter length of mesoscutum (holotype) but sometimes shorter, not carinate anteriorly but abruptly angled into anterior face of pronotum which is vertical to dorsal plane of mesonotum, pronotal neck concealed in dorsal view; mesoscutum 2.3 times as long as broad; scutellum almost circular and almost as long as combined length of mesoscutum and pronotum; sculpture of thoracic dorsum finely reticulate, dull, areoles on scutellum only about half diameter of those on mesoscutum, pronotal collar without posterior shiny strip; mesepisternum with ventral half weakly reticulately sculptured. Propodeum medially about 0.4 times as long as scutellum; median area between lateral plicae rather more than twice as broad as long, median carina extending over about anterior two-thirds, divided posteriorly into two carinae which run into the curved, converging lateral plicae behind well-developed apical foveae; nucha short; median area and nucha smooth, shiny; spiracles about one-third of median length of propodeum, almost touching metanotum. Legs rather stout, pro- and metafemora about 3.3 times as long as broad.

Forewing: costal cell bare on upper surface, a few setae on apical one-third of under surface; basal cell and basal vein bare; speculum large, open below, extending to stigmal vein on upper surface as a strip behind marginal vein; disc of forewing quite densely setose, but setae short and pale; apical fringe developed. Lengths of costal cell: marginal vein: stigmal vein: postmarginal vein as 325:152:134: 148 in holotype, somewhat variable, but marginal vein always slightly longer than postmarginal vein and postmarginal vein 1.1 to 1.3 times as long as stigmal vein.

Gaster: ovate, 1.1 (holotype)—1.3 times as long as rest of body and twice as long as broad, slightly narrower than thorax; basal tergite occupying about one-fifth of total length, its posterior margin evenly curved; last tergite slightly broader than long; ovipositor sheath somewhat projecting; apex of hypopygium about 0.4 times gaster length.

Male ( Fig. 20 ). Length 1.0– 1.3mm. Head and mesosoma purplish black, only face and propodeum with greenish tints; gaster (including aedeagus) entirely bright testaceous, almost orange. Antenna except clava pale testaceous; clava with two basal segments dark brown, third segment mostly pale yellowish. Legs with coxae mostly concolorous with thorax, otherwise bright yellowish testaceous excepting brown tarsal claws.Wings faintly brownish.

Head ( Fig. 22 ): with reticulate sculpture, that on gena just behind malar sulcus rather finer than elsewhere but shining, without patch of very fine, dull sculpture. Antenna with scape about 10 times as long as broad, not reaching level of anterior ocellus; pedicel plus flagellum 0.8 times as long as breadth of head; pedicel almost as long as anelli plus first funicle segment; flagellum thin basally, first funicle segment scarcely broader than third anellus and only half as broad as pedicel, funicle segments 1–4 slightly longer than broad, fifth funicle segment quadrate, about 0.7 times as long as pedicel and slightly narrower than clava; clava ovate, about 2.5 times as long as broad.

Gaster: oval, about as long as mesosoma.

Material examined. Holotype: ♀, Malta, Migra Ferħa, 3.vi.2012, D. Mifsud, ex galls of Asphondylia scopuli ( Diptera , Cecidomyiidae ) on Atriplex lanfrancoi , emerged between 23–30.vi.2012, deposited in the National Museums of Scotland, Edinburgh ( NMS). Allotype: ♂, same data as holotype, emerged between 5 and 20.vi.2012, deposited in NMS. Paratypes: 7♀, same data as holotype, emerged 23–30.vi 2012; 14♂, same data as holotype, emerged 5–20.vi.2012; other material examined: 2♀, 5♂, same data as holotype, emerged as holotype and allotype respectively; 1♀, same data as holotype, emerged 30.vi.2012; 1♂, same data as holotype, emerged 23.vi.2012. paratype depositories: 2♀, 2♂ NMS; 2♀, 3♂ TAUI; 2♀, 3♂ in private collection of DM; 1♀, 6♂ in private collection of RA.

Etymology. Mesopolobus melitensis is named after Melita, an ancient name for the island of Malta.

Comments. Mesopolobus melitensis belongs to a small group of species which are parasitoids in galls of Cecidomyiidae and characterized by a short, squat mesosoma with the mesoscutum about twice as broad as long. Females have blackish bodies with purplish tints but males are more greenish, with pale legs, and gasters more or less yellowish. Antennae in both sexes have three anelli and five funicle segments. In females of this group, the antennal clava is usually paler than the remainder of the antenna, but in males (where known) it is mostly darker.

The group has a Mediterranean distribution and comprises Mesopolobus maculipennis ( Mercet 1923) (reared from galls of Stefaniola on Salsola ), M. flaviclavatus ( Ferrière 1952) , M. meridionalis Garrido & Nieves-Aldrey (1996) and M. melitensis , together with an undescribed species from Spain and Portugal (reared from galls of Stephaniella atriplicis (Kieffer) on Atriplex halimus , an unidentified cecidomyiid in flowers of Halimione portulacoides , and Rhopalomyia on Artemisia ) mentioned by Askew et al. (2001) as M.? flaviclavatus . The hosts of M. flaviclavatus and M. meridionalis are unknown.

Females of M. melitensis may be distinguished from those of M. flaviclavatus and M. meridionalis by the relative length of the gaster, which in M. flaviclavatus is nearly 1.6 times as long as the rest of the body (and described as fiery red laterally and ventrally) ( Ferrière 1952, von Rosen 1960), and in M. meridionalis only 0.7 times as long. In both M. melitensis and M. maculipennis the female gaster is 1.1–1.3 times as long as the combined lengths of head and mesosoma. The forewing of M. melitensis has a complete apical fringe, but in M. maculipennis this is absent between the end of the postmarginal vein and the wing apex. Also, the postmarginal vein in M. melitensis is nearly as long as the marginal vein, whereas in M. maculipennis it is only about 0.7 times as long. In females of M. melitensis the whitish clava contrasts conspicuously with the dark funicle segments, but in females of M. maculipennis the color difference between clava and funicle segments is much less evident. The head of M. melitensis in profile is narrower than that of M. maculipennis , and the tegula in M. melitensis is dark, whereas in M. maculipennis it is pale. The male of M. melitensis has an entirely bright yellowish-orange gaster and differs strikingly from that of M. maculipennis in which the gaster is dark with pale coloration restricted to part of the ventral surface and a broad sub-basal band on the dorsal surface. Males of M. flaviclavatus and M. meridionalis are unknown.

Figures

FIGURES 19–22. Mesopolobus melitensis. 19. Female, lateral. 20. Male, lateral. 21. Female, head, frontal. 22. Male, head, frontal.