Platyja yaleyambae, Zilli & Vos, 2021

Zilli, Alberto & Vos, Rob de, 2021, The sumatrana species group of the genus Platyja with descriptions of four new species (Lepidoptera: Erebidae), Fragmenta entomologica 53 (2), pp. 391-410 : 407-408

Platyja yaleyambae sp. n.

Description

Male (Figs 13-15)

Habitus. Forewing length 28-32 mm. Outward form and pattern indistinguishable from male P. subtracta sp. n.

Male genitalia (Figs 46-48, 58-60). Apparatus, phallus sheath and vesica as in P. subtracta sp. n., except for the diverticulum bearing more cornuti which is long and gradually tapered towards the apex and bears a continuous stripe of very small cornuti up to its tip.

Female (Figs 23-24)

Habitus. Forewing length 28-32. Outward form and pattern indistinguishable from female P. subtracta sp. n.

Female genitalia (Figs 69, 74). As in P. subtracta sp. n., with more weakly sclerotised cervical part of bursa copulatrix.

Material examined. Type material. [ Papua New Guinea: Milne Bay Province]: Holotypus: ♂, Louisiade Archipelago: Sudest Isl. [= Vanatinai, Tagula], Jan.-May 1916, Eichorn Bros. ( Rothschild Bequest 1939-1), NHMUK014165473 , in NHMUK (Fig. 13) ;

Paratypi (9♂♂, 12♀♀): 2♂♂, 2♀♀, Sudest Isl. , Mt. Riu, Jan.-Feb. 1916 ; 4♂♂, 5♀♀, idem, 2000 ft, March 1916 , Eichorn Bros.; 1♂, 1♀ idem, April 1916 ; 1♂, idem, Jan.- May 1916 ; 2♀♀, Sudest Isl. , Jan.-May 1916 , Eichorn Bros.; 1♂, 2♀♀, Sudest Isl. , Mt. Riu, Jan.-Feb. 1916 , Eichorn Bros. (recu de Janson); these (9♂♂, 12♀♀) in NHMUK ;

Non-type material (2♂♂): 1♂, Rossel Isl. [= Yela], Mt Rossel, 2100 ft, Nov. 1915 - Jan. - [1]916, W.F. Eichorn; 1♂, idem, Dec. 1915; both in NHMUK .

Distribution. Sudest (= Vanatinai, Tagula) and Rossel (= Yela) islands in the southeastern sector of the Louisiade Archipelago ( Fig. 76 ).

Diagnostic remarks. The only real diagnostic feature of P. yaleyambae sp. n. from its allopatric sibling P. subtracta sp. n. has so far been found in the configuration of the vesical diverticulum bearing more cornuti. This is short and abruptly constricted before thin, finger-like tip in subtracta , contrary to the much elongate conical one of yaleyambae . The cornuti are fewer and much bigger in subtracta , and do not extend into the finger-like tip, while those of yaleyambae are numerous, much smaller and reach the tip of the diverticulum. The other main diverticulum branch- ing from the vesical corpus, that tipped by a single stout cornutus, is also comparatively smaller and shorter in the Louisiades species, so that actually the two main diverticula in this species are of comparable length, while in subtracta such diverticulum is twice as long as the other. In the female genitalia there is indication of some allomorphic differences between the two species in the posterior trochoidal section of the bursa copulatrix, but the mem- branous constitution of this part makes it difficult to pa- rameterise any shape differences. More evident though is the stronger sclerotization of the cervical part in subtracta .

Taxonomic remarks. The background for erection of P. yaleyambae sp. n. as a new species distinct from P. subtracta sp. n. looks similar to that between P. vityaz sp. n. and the yet unnamed population from New Britain (see above), differences essentially regarding one single vesical diverticulum or swelling and its cornuti. However, in this case the availability of several specimens from the type locality and the assessment of the range of variability of that diverticulum in subtracta across whole New Guinea (specimens from the Milne Bay area facing the Louisiade Archipelago having also been dissected) indicate that such differences are fixed. It is worth noting that in Fergusson Island (D’Entrecasteaux group), not far from the SE Louisiades but much closer to New Guinea, P. subtracta sp. n. has been found. Platyja yaleyambae appears therefore to be a close sibling of P. subtracta that has likely originated as an offshoot of the species in the main island that diversi- fied by virtue of the stronger isolation, and currently is the most easterly distributed species of the sumatrana -group.

Etymology. The species is named after the Local Level Government area “Yaleyamba”, which comprises the eastern part of the Louisiade Archipelago, with Sudest (= Vanatinai, Tagula) and Rossel (= Yela) islands. The name is a noun in the genitive case.

Figures

Fig. 76 – Distribution of species of the Platyja sumatrana-group (populations from New Britain and Rook Island [= Umboi, Siassi] combined as vityaz s.l.; see explanation in text).