Megaprosternum norfolcensis ( Dodd, 1924 )

Colombo, Wesley D. & Azevedo, Celso O., 2024, Revision of the strongly flattened Megaprosternum Azevedo (Hymenoptera, Bethylidae), European Journal of Taxonomy 958 (1), pp. 1-47 : 28-31

Megaprosternum norfolcensis ( Dodd, 1924)

Fig. 10

Sclerodermus norfolcensis Dodd, 1924: 184–185 .

Sclerodermus norfolcensis – Hawkins 1942: 883. — Naumann 1990: 20, 22, 26. — Lanes & Azevedo 2008: 81, 83. — Azevedo et al. 2020: 478.

Scleroderma norfolcensis – Smithers 1998: 44.

Megaprosternum pentagonal – Lanes & Azevedo 2008: 81.

Megaprosternum norfolcensis – Azevedo et al. 2018: 235.

Differential diagnosis

The females of this species differ from those of the other species by having the head at most 1.2× as long as wide, the median clypeal lobe straight, the antennae with 11 flagellomeres, the mesoscuto-scutellar foveae absent and wings polymorphism, with macropterous and apterous forms.

Material examined

Holotype

AUSTRALIA – Norfolk Island • ♀; “Norfolk Island, rotting leaves, A.M. Lea (type 14585)”; SAM. [By description.]

Non-types

AUSTRALIA – Norfolk Island • 2 ♀♀; “ Norfolk Island , under decayed palm leaves M.T. Pitt , 1.000 ft. 12.vi.1939, I. McComish, 156, Brit. Mus. 1940-154”; NHMUK 015663882 , 015663883 . – Queensland • 1 ♀; “ Peachester , 19.iii.1974, R.A. Yule , Dept. For. Qld., Nicher Accn. nº. 722, C.I.E. A8556”; NHMUK 015663884 . [Previously identified as M. pentagonal by Lanes et al. (2008).]

Redescription

Female

MEASUREMENTS (mm). Body length 3.0‒ 3.4 mm; LH 0.75; WH 0.65; WF 0.45; WOT 0.12; surface of median clypeal lobe 0.38; HE 0.25; OOL 0.40; LFW 2.15.

COLOR ( Fig. 10A ). Head, mesosoma and metasoma dark castaneous.

HEAD ( Fig. 10B ). Oval, in lateral view; sides almost parallel, in dorsal view; malar space 0.2× HE; median clypeal lobe straight, as long as lateral ones, with pair of lateral carinae, converging posteriorly, lobe delimitation indistinct; mandible with three apical teeth; antenna with 11 flagellomeres, pedicel longer than flagellomere I; eye weakly setose, contour not protruding; frons coriaceous; ocellar triangle with anterior angle acute, postocellar line longer than DAO.

MESOSOMA. Pronotal flange polished, with posterior margin at most 1.5× as wide as anterior one; dorsal pronotal area coriaceous, posterior margin almost straight; mesoscutum longer than mesoscutellum medially; parapsidal signum absent; transscutal fissure inconspicuous; mesoscuto-scutellar suture absent; metapectal-propodeal disc longer than wide medially, without evident constriction at propodeal spiracle; transverse anterior carina absent; lateral marginal carina absent; paraspiracular sulcus absent; paraspiracular carina absent; metapostnotal median carina absent; propodeal spiracle circular, on lateral surface of the metapectal-propodeal complex; forewing with prestigmal abscissa of radial 1 subrectangular, 4.0 ×as long as pterostigma, 2.0×as wide as Sc+R vein, prestigmal flexion line present, pterostigma small and circular; hind wing with three equidistant distal hamuli.

METASOMA. Second abdominal spiracle circular; abdominal tergum narrowing apicad.

Male

Unknown.

Variations

The vertex of the head can be angled ( Fig. 10B ), as observed in the specimens from Norfolk Island, while it can be rounded ( Fig. 10C ), as seen in the specimen from Queensland. The wings can be present and well developed (macropterous form) as in the holotype and the specimen from Queensland, whereas they can be absent (apterous form) as in the three paratypes.

Remarks

This species is known only from four female specimens collected on Norfolk Island; a subtropical island located in the South Pacific Ocean. Dodd (1924) highlighted the wing polymorphism in this species, stating that “of the four specimens, three are apterous”. Although Dodd (1924) did not explicitly state how the association of the two forms (apterous and macropterous) was made, based on the author’s statement “there appear to be no structural differences between the two forms”, it can be inferred that, as the only variation lies in the wing development, the author associated them due to the morphological similarity.

Naumann (1990) stated that this species is endemic to Norfolk Island and is known for submacropterous (probably brachypterous or micropterous forms) females and macropterous males. However, after an extensive literature review, we did not find the description of the males of this species, and as a result, they are considered unknown at this time. Interestingly, he mentioned that females are submacropterous. However, upon examination of the provided forewing drawings of females ( Naumann 1990: fig. 21), it is evident that they possess wings typical of a macropterous pattern, similar to the holotype. Consequently, we found no evidence to support the presence of micropterous or brachypterous forms in this species, as observed in other species such as M. pentagonal , for instance.

We did not have access to the holotype and the apterous paratypes mentioned by Dodd (1924). However, it is probable that the paratypes are micropterous, as reported for M. pentagonal (see below) and several species of Sclerodermus Latreille, 1809 (see Azevedo & Colombo 2022b). Nevertheless, a thorough study of these specimens is necessary to confirm whether they exhibit microptery or aptery. In contrast, the apterous specimen (NHMUK 015663882) studied by Hawkins (1942), upon closer examination, appears to be a macropterous specimen with a damaged wing, supported by the division of the mesonotum into anteromesoscutum and mesoscutellum.

We are considering the specimen from Queensland (NHMUK 015663882) as belonging to the species M. norfolcensis , despite its head vertex being angled, in contrast to the holotype and other paratypes which have a rounded head vertex. This decision is supported by the consistent diagnostic morphology of the species, as listed in the Differential diagnosis section, which remains consistent across specimens. Furthermore, given the substantial volume of new material added compared to what was previously known about Megaprosternum , it is prudent, for the time being, to maintain this classification as belonging to the same species.

Host

Probably parasitic on larvae of Coleoptera Linnaeus, 1758 in wood or litter ( Naumann 1990).

Distribution

Australia ( Norfolk Island and Queensland).

Figures

Fig. 10. Megaprosternum norfolcensis (Dodd, 1924). A–B, D. Non-type, ♀ (NHMUK 015663883). C. Non-type, ♀ (NHMUK 0015663884). A. Habitus, dorsal view. B–C. Head, dorsal view. D. Labels. Scale bars: A = 500 μm; B–C = 250 μm.