Betasyrphus keiseri Ssymank, 2010, sp. n.
Creators: name: Ssymank, Axel
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Syrphidae
Betasyrphus
Betasyrphus keiseri

description: Betasyrphus keiseri sp. n.
(Figs 1–6 and 8–15)
= serarius Keiser 1971, not Wiedemann 1830 (misidentification)
= serarius v. Doesburg 1957, not Wiedemann 1830 (misidentification) = serarius de Meyer et al. 1990, not Wiedemann 1830 (misidentification)
Material in the Keiser collection (NHMB) had no individual determination labels. They were published as “ Metasyrphus serarius Wied. ” in Keiser (1971). Of the four specimens from v. Doesburg (1957) mentioned in Keiser (1971) only one male could be found in the collection of Stuckenberg (NMSA) with the original determination label of v. Doesburg.
Material examined. Holotype: 3, “ Madagascar Fia. [Fianarantsoa province] Vohipara [Ramonafana National Park], 13.IX. [19]59, F. Keiser”, approx. 21°16’S, 47°26 E (NHMB). A red label was added: “ Betasyrphus keiseri HOLOTYPE, A. Ssymank” (Fig. 4). Genitalia preserved and associated in glycerine in a vial on the same pin as the type specimen.
Allotype: Ƥ “ Madagascar, Tan., / Manjakatompo, 3.1.[19]58, F. Keiser”, approx. 19°20’S, 47°26’ E. (NHMB). A red label was added: “ Betasyrphus keiseri ALLOTYPE, A. Ssymank” (Fig. 4).
Paratypes: Madagascar: 9 3 Fianarantsoa Province, Vohipara, 15.IX.1958, F. Keiser (NHMB, SSY); same but 13.IX.1958 (NHMB); 4 3, Ƥ Antananarivo Prov., Manjakatompo, 3.I.1958, F. Keiser” (NHMB); Ƥ: same but 23.IV.1958 (NHMB); 3: Antananarivo Prov., Tananarive, 8.VII.1958, F. Keiser (NHMB); 3 Ƥ: same but 5.IX.1958, 1.IX.1958 and 7.VII.1958, F. Keiser (NHMB); 3: Manjakatompo, forest station, Ankaratra massif, Jan. 1956, B. Stuckenberg, “ Syrphus serarius 3, det. V. Doesburg” (NMSA); 3: Madagascar CentreVakoana 1520 m NN, Andringitra Ambalavao, 21–24. I.1958, B. Stuckenberg (NMSA); 2 3: Madagascar Centre, Plateau Soaindrana, 2060 m NN, Andringitra Ambalavao, 14–17. I. 1958, B. Stuckenberg (NMSA); 3: Madagascar Centre, Anjavidilava 2020 m NN, Andringitra Ambalavao, 17–21. I. 1958, B. Stuckenberg (NMSA); 3: Fianarantsoa Prov., 12 km W Ramonafana NP entrance, radio tower, malaise in montane tropical forest 7.VI. – 18.VI.2003, A. H’Hala, ME Irwin, 1215 m, 21°15.05’ S, 47° 24.43 E, MG 98_63 (CAS); 2 Ƥ: Antananarivo Prov., Mandraka, 4.IV.1958, F. Keiser (NHMB); Ƥ: D.-S., Mtge. d'Ambre, 23.V.1958, F. Keiser (NHMB); 2 Ƥ: Antananarivo Prov., Ambohitantely, 10.VI.1958, F. Keiser (NHMB); Ƥ: same but 8.VI.1958 (NHMB); Ƥ: Madagascar Centre, Ankazokivady, 1640 m., 25.VII.57, F. Griv., Institut Scientifique Madagascar (NHMB); 2 Ƥ: FO 5381, 18°54'43" S, 47°54'51" E, Mandraka, 4 km W, river bank, 1250 mNN, on Ageratum conyzoides, 28.10.2003, A. Ssymank (SSY); 3 Ƥ: FO 5383, 18°55'36" S, 48°24'53" E, Andasibe (Périnet), E of Moramanga, 940 mNN, on Ageratum conyzoides, 29.10.2003, A. Ssymank (SSY); Ƥ: “FO 5384, 18°37'33" S, 48°19'41" E, Ampasimpotsy, 3 km N, Andasibe, 960 mNN, 29.10.2003, A. Ssymank (SSY); 6 Ƥ “FO 5391, 48°54'45" S, 47°54'53" E, Mandraka, 4 km W, half shaded brook, 1270 mNN, 31.10.2003, A. Ssymank (SSY); 3 Ƥ „FO: 5396, 21°13'11" S, 47°21'59" E, Ambodifanimena, 12 km WNW of Ranomafana, 1220 mNN, 0 3.11.2003, A. Ssymank (SSY); 2 Ƥ „FO: 5399, 21°12'41" S, 47°21'52" E, Ambodifanimena, clearing in secondary mountain rain forest and shrubs on the river bank, 12 km WNW of Ranomafana, 1166 mNN, 0 5.11.2003, A. Ssymank (SSY); Ƥ Grande Comore, Forêt de Kartala, Convalescence, 1680 m, 20–21 XI 1973 L. Matile leg (MNHN); Ƥ: Madagascar Centre, Pic Boby 2400 m, Andringitra Ambalavao, 11–14. I.1958, B. Stuckenberg (NMSA); Ƥ: Fianarantsoa Prov., Belle Vue, 1,2 km S Ramonafana NP entrance, malaise in rainforest 28.XI / 6.XII.2001, 1095 m., A. Harin’Hala, ME Irwin, 21°15.99’ S, 47° 25.21 E, MG 90_05“ (CAS); Ƥ: \, Fianarantsoa Prov., Ranomafana NP, road from ValBio to Ranomafana, X. Mengual 25-11-2004 (CEUA) (in ethanol); Ƥ:, Fianarantsoa Prov., Ranomafana NP open area in front of ValBio, X. Mengual 19-11-2004 \ DNA voucher specimen, Lab. No XP 101, X. Mengual CIBIO, Alicante, Spain ” (ZMUH) (abdomen missing, in ethanol); Ƥ: same, but (USNM) (in ethanol); Ƥ: Fianarantsoa Prov., Ranomafana NP Sakaroa, marsh area, 24-11-2004, X. Mengual” (USNM) (in ethanol); Ƥ: Fianarantsoa Prov., Ranomafana NP, open area in front of ValBio. 21-11-2004.: X. Mengual.\ DNA voucher specimen, Lab. No XP 55, X. Mengual CIBIO, Alicante, Spain ” (ZMUH) (head separated from thorax, abdomen missing, in ethanol).
For all paratypes a yellow label was added: “ Betasyrphus keiseri, PARATYPE, A.Ssymank”. “FO”- numbers refer to the electronic database of the author with additional details on the localities.
Description: Body length: male 9–11 mm, female 8–10.5 mm.
Wing length 7–10 mm (from proximal margin of costagium to apex).
Male: Head. Eye with gradually enlarged facets dorsally, with dense long hairs (see Fig. 8 & 9) on the whole surface. Hairs on eye more brownish dorsally, more whitish ventrally towards mouth. Eye contiguity about as long as ocellar triangle which is shining with long black pile. Occiput with dense whitish pollinosity, long black simple bristles close to the eye margin and behind several dense rows of yellowish (dorsally) to white (ventrally) flattened, feathery branched hairs. Frontal angle approximately 90°. Frons dark with golden pollen toward the eye margin and long black hairs. Face completely yellow including knob, laterally and below antennae extensively whitish pollinose. Oral margin largely yellow. Lunula brownish. Proboscis short, 1.5–2 mm.
Antenna. (Fig. 5): Scape and pedicel black, postpedicel dark brown with ventrally and basally gradually lighter orange colour, especially internally. Length ratio of postpedicel ca. 1.5:1 (L/W). Arista yellowbrownish, bare and slightly longer than length of pedicel. Proximal margin of pedicel on its inner side distinctly curved.
Thorax. Mesoscutum black, almost shining with faint pollinosity and entirely covered with long, yellow, wavy hairs. Two vague pollinose vittae can be detected looking over the head backwards with appropriate lighting in the right angle. Scutellum yellow with long, wavy, yellow hairs on disc and long, black, wavy hairs about the length of the scutellum on its hind margin. Basoventral corners of the scutellum in lateral view narrowly black. Subscutellar fringe consisting of dense, long, white hairs.
Pleura mostly black, covered with dense whitish pubescence, weaker pollinose around metathoracic spiracle. Large parts of the pleura with long, yellow to whitish hairs. Postpronotum, anterior anepisternum, meron metepimeron and metepisternum without long hairs. Metasternum bare.
Legs. Legs simple, femora and tibiae completely yellow, trochanter dark brown to black. Coxae brownish black with white pollinosity. Tarsi with first tarsomere yellow, apical tarsomeres of all legs more or less darkened. All femura ventrally with long yellow hairs, all tibiae with short yellow hairs. Metabasotarsomere mainly yellow haired, apical tarsomeres largely black haired in all legs, claws bicolorous, yellow at base and black at apex.
Wing. Wing clear, most of specimen with diffuse brownish blotch anteriorly in middle of wing below the pterostigma extending backwards for about half of the wing width (Fig. 12), but some males with completely hyaline wings. Pterostigma unicolourous brownish. Apical half of the wing (including complete R4+5) and alula completely covered with microtrichia (Fig. 13). Basal parts of the wing with large areas bare of microtrichia (especially in bm, br, cup anterior margin). Lower calypter greyish with scattered long hairs on the surface and a brown hair fringe along margin in addition to the microtrichia. Halter with a light brown stem and whitish knob.
Abdomen. (Fig. 3) Tergite 1 dark with a bluish tinge, weak white pollinosity and long white hairs. Tergite 2 black with a narrow grey pubescent fascia not reaching side margins. Hairs on tergite 2 long, yellow, and with additional shorter, black hairs on the posterior part. Tergites 3 and 4 brownish with narrow pubescent fasciae widely separated from anterior margin and not reaching side margins. Tergite 3 in the anterior half with long yellow hairs, posterior half with long black haris. Tergite 4 mainly black haired, with only a few yellow hairs anteriorly and laterally on the white pollinose fascia. Sternites 2 to 4 broadly pollinose along their margins, covered with long yellow hairs. The center of these sternites each with a shining black macula, covered with additional short black hairs.
Pregenital segments with long black hairs.
Genitalia. Genitalia as in Fig. 14, 15. Styli not elongated (in contrast to elongated styli of B. nipponensis). Very similar to the genitalia of B. serarius. Styli: Length:width ca. 2.5: 1, gradually narrowed towards the apex, slightly broader than in B. serarius, cerci slightly narrower than in B. serarius, superior lobe of theca with a small hook in lateral view (rounded in B. serarius). Tube of adaeagus long, lower lobe of theca bifurcate.
Female (Fig. 10, 11). Differing from male as follows:
Head. Frons ca. 1/6 of total head width at level of apical end of ocellar triangle. Frons black except a small yellowish to brownish margin above the yellow lunulae. Upper frons and ocellar triangle shining black, lower frons with dense, white pollinosity covering about 1/2 –2/3 of its length. Whole frons covered with long black hairs. Antenna usually slightly longer than in male, length ratio of postpedicel ca. 2: 1 (L/W, Fig. 6).
Wing. Clear transparent, in half of the specimens with a very slight infuscation in the middle part of the wing in a similar position as in most males.
Abdomen. Tergites 3 and 4 sometimes with obscure yellow fascia beneath the pollen visible laterally.
Diagnosis: Face including knob yellow (knob black in B. serarius, see also Tab. 1), pterostigma unicolorous at most proximal borderline darkened, antenna not elongated (postpedical L:W usually 1.5– 2: 1) (elongated in B. stuckenbergi, L:W ca. 3:1), lower side of postpedicel basally broadly orange, no clear yellow maculae or fasciae on the tergites, but on tergites 2–4 narrow silvery pollinose fasciae, widely separated from anterior margin of tergites, not reaching side margins. Wing usually with diffuse brownish blotch. Other characters see Tab. 1.
Etymology: The name keiseri was chosen in honour of Fred Keiser (17.II.1895 – 21.VIII.1969), for his extensive collection and studies of Madagascar Syrphidae. He described a large proportion of the species known from this subregion. Most of the known material he studied was collected by him and is deposited in the NHMB.
Distribution: All known specimens have been found in Madagascar and the Grandes Comores, at altitudes ranging from 940 to 2400 m a.s.l. (Fig. 1, distribution map). The specimens from Madagascar are mainly associated with mountain areas and rain forest or rain forest remnants.
Biology: Keiser (1971) gave no notes or observation on habitat and behaviour. According to own observations and label data of available material, specimens have been collected in mountain areas with rainforest or secondary rainforest remnants, along forest margins with flowers or sitting on leaves, observed close to streams or brooks, showing typical hovering behaviour in sun-lit patches.
Flower visiting: probably a wide range of flowers with easily accessible nectar, so far observed from Ageratum conyzoides L. (Asteraceae). Flight period: April – July and September to January, but probably flying throughout the year with an optimum in winter. The number of known specimen is insufficient to decide whether the species is bivoltine or polyoltine.
Larvae are unknown but presumably aphidophagous.
description: Published as part of Ssymank, Axel, 2010, Review of the species of Betasyrphus Matsumura, 1917 (Diptera: Syrphidae) from Madagascar with description of a new species, pp. 40-50 in Zootaxa 2417 on pages 41-46, DOI: 10.5281/zenodo.294068