Biston rosenbaueri sp . n . ( Lepidoptera , Geometridae , Ennominae ) from the Balkan Peninsula

A new species of Biston from the Balkan Peninsula is described. This species, Biston rosenbaueri sp. n., has been previously overlooked for a long time. The species is nearest to Biston strataria (Hufnagel, 1767) and also close to B. achyra Wehrli, 1936. Male genitalia and barcoding data are compared for these externially similar species from the Western Palaearctic. Zusammenfassung. Nahestehend den Arten Biston strataria (Hufnagel, 1767) and B. achyra Wehrli, 1936 wird eine dritte bisher übersehene Art, Biston rosenbaueri sp. n., vom Balkan beschrieben. Die männlichen Genitalien und die Barcodedaten werden mit denen der bisher bekannten ähnlichen westpaläarktischen Arten verglichen.


Introduction
The genus Biston contains more than 50 species (Scoble and Hausmann 2007).Their distribution area covers the Holarctic and Oriental regions as well as Africa.All species are large and robust, with a wingspan between 30-80 mm, and with females often larger than males.The abdomen, thorax and tegulae are covered in a dense vestiture of scales giving a furry-appearance.The antennae are bipectinate in males, while filiform in females.On the forewing venation, Sc is free, whereas R1 and R2 are usually stalked.R2 is sometimes connected with R3-R4 or R3-R5 by a transverse bar.R3-R5 is not stalked with M1.On the hindwing Sc + R1 is close to the cell, while M1 runs from the anterior angle of the cell, but M2 and A3 are absent.CuA1 forks off before or from the posterior angle of cell (Jiang et al. 2011).
In Europe (Müller 1996) and other parts of the Western Palaearctic, two similar Biston species are known so far, namely the widespread B. strataria (Hufnagel, 1767) and B. achyra Wehrli, 1936 described from eastern Turkey but known from the Caucasus, Transcaucasus and Turkmenistan (Viidalepp 1996).Beshkov (2017) reported the occurrence of B. achyra from Bulgaria, figuring the adult moths as well as male genitalia.DNA barcodes from this Bulgarian material was left as a task for the future.Both species have also been reported from the Greek island of Samos (Fritsch et al. 2014).
These moths are on wing in early Spring, when undoubtedly the dense thoracic scaling aids in thermoregulation.
Recently, Frank Rosenbauer and Peder Skou collected male Biston specimens in Greece, while Egbert Friedrich collected similar specimens in north-western Croatia.Examination of this material reveals the presence of a third, hitherto unknown species morphologically similar to B. strataria Nota Lepi.41(2) 2018: 207-213 | DOI 10.3897/nl.41.25099 and B. achyra.The results of DNA barcoding confirm the separation of this third species.In this article, this new species is described and its morphological characters are illustrated.Further investigations are needed to clarify whether the Bulgarian specimens (or some of them) belong to this new species.

Materials and methods
The publication is based on material obtained from the following institutional and private collections:

Morphological studies
For genitalia preparations, a standard procedure (Robinson 1976) was followed.Genitalia dissections were made using a stereo microscope CARL ZEISS JENA SM XX.After maceration, the genitalia preparations were stained with Chlorazol Black and embedded in Euparal.Genitalia slides were photographed using a Leica Z16APO digital stereo-microscope equipped with a DFC 49 camera in SMNS by Hossein Rajaei.Adult specimens (except for Fig. 2) were photographed using a Panasonic DMC-FZ50 digital camera with Leitz ELPRO 1 and two close-up lenses.

DNA barcoding
After sending legs for extraction to Guelph, a 658bp fragment ("DNA barcode") of the mitochondrial COI gene was amplified and sequenced at the Canadian Centre for DNA barcoding (CCDB, Guelph), in the framework of the Lepidoptera Campaign of the international Barcode of Life programme (iBOL).Altogether, barcode data from 72 Biston species were used.

Description
Biston rosenbaueri sp.n. Adult male (Figs 1,2).Wingspan 40-45 mm.Abdomen, thorax, tegulae very hairy.Forewing: Ground colour white, densely suffused with light and dark brown, sometimes also black scales, together giving a pale grey or brownish impression.Veins brown or black.Postmedial and antemedial line distinct, black, on veins thickened, forming small triangles pointing towards the wing base.Postmedial line undulating, angled on vein M3 and M2.Antemedian line bent, sharp or more diffuse, sometimes angled on M3 and A. Medial line indistinct.Postmedial line on outer margin, antemedial line on inner margin with a broad pale brown band, in darker specimens indistinct.Terminal area with a diffuse whitish line, sometimes absent.Discal spot distinct, slightly blurry.It lies between the postmedial and the medial line.Hindwing less suffused with dark scales, therefore paler than the forewing.Its postmedial line nearly straight, its medial line diffuse, straight.Discal spot present as a distinct dot.Both wings with fringes weakly chequered brownish and grey.Labial palpi also very hairy, medium brown, frons rough-scaled, whitish.Patagia anteriorly whitish, posteriorly black.Tegulae whitish, irrorated with more or less black scales.Thorax greyish-brown as for tegulae.Abdomen beige and grey scaled.Antennae of males bipectinate with noticeable reddish-brown ciliated processes and variegated shaft.Hindtibia with 2 + 2 spurs.Female unknown.

Differential diagnosis.
The new species is very similar to its relatives Biston strataria (Hufnagel, 1767) (Fig. 4) and B. achyra Wehrli, 1936 (Fig. 3).Biston rosenbaueri sp.n. males can be separated from B. strataria by the distinct discal spot on hindwings, which is absent or hardly visible in B. strataria.B. achyra has on average less contrasting wing pattern, its tegulae and thorax are brownish grey and have no white blotches as can mostly be seen in B. rosenbaueri sp.n. and B. strataria.This species has also a distinct discal spot on hindwings.See Figs 1-4.In comparison with B. strataria, B. rosenbaueri sp.n. on forewing has postmedial line between the veins CuA2 and A2+A3 less excurved, oval, not somewhat conic tongue-like as it is in B. strataria; but more prominent than in B. achyra.Antemedial line in B. rosenbaueri sp.n. also looks less extended along the A2+A3 than in B. strataria, but similar to that in B. achyra.For differences in male genitalia, see Table 1.
Distribution.Biston rosenbaueri sp.n. is known from northern Croatia and northern Greece.The specimens have been collected at elevations between 200 and 1000 m.
Biology.Unknown Etymology.The new species is named after the German lepidopterologist Frank Rosenbauer who collected male specimens of the new species in Greece.

Discussion
It was rather surprising to find a new large Biston species in the Balkan Peninsula.Future work will focus on the study of the overall distribution and biology of the new species.The description of the hitherto unknown female could improve the morphological differentiation to the known species Biston strataria and B. achyra.

Table 1 .
My great thanks go to Egbert Friedrich, Jena, DieterFritsch, Lörrach, Michael Leipnitz, Stuttgart, Wolfram  Mey, MNHU, Peder Skou, Vester Skerninge and Frank Rosenbauer, Münster,for loan of material and/or sending photos of adult specimens of the new species and its near relatives and for permission to include their material in this paper.I thank Evgeny A. Beljaev from the Federal Scientific Centre of the East Asia Terrestrial Biodiversity, Vladivostok, Claudio Flamigni, Stanislav Gomboc, Erki Õunap, and other reviewers for their helpful advice.I also thank Axel Hausmann from the Zoologische Staatssammlung Munich for contributing the genetic data, and Hossein Rajaei, State Museum of Natural History, Stuttgart, for making the genitalia photos and critical review of the manuscript, both also for helpful discussions.Many thanks for English editing to David Lees.Differential characters in the male genitalia of B.strataria, B. rosenbaueri sp.n. and B. achyra.