Citrogramma robertsi, WYATT, 1991

Mengual, Ximo, 2012, The flower fly genus Citrogramma Vockeroth (Diptera: Syrphidae): illustrated revision with descriptions of new species, Zoological Journal of the Linnean Society 164 (1), pp. 99-172 : 159-161

CITROGRAMMA ROBERTSI WYATT, 1991

Citrogramma robertsi Wyatt, 1991: 161 . Holotype: ♀, BMNH, by original designation. Type locality: Papua New Guinea: Bulolo. Wyatt, 1991: 156, 161, figs 1, 11.

Description

Male: Head: Face with facial tubercle, gradually sloping dorsally, more abrupt ventrally, yellow with medial dark vitta, from oral apex to antennal basis, narrower than yellow lateral areas of face, black pilose dorsal and medially, yellow pilose on ventral portion, white pollinose laterally and ventrally; gena yellow, mainly yellow pilose with little black hairs, white pollinose posteriorly; holoptic; lunule dark; frontal triangle yellow with anteromedial black triangular area pointed posteriorly, black pilose; vertical triangle black, slightly longer than eye contiguity (1.3:1), black pilose ( Fig. 27 ); ocelli reddish; antenna dark brown, black pilose on scape and pedicel; basoflagellomere orangish, dark dorsally, oval; arista black; occiput blackish, silver pollinose, white pilose on ventral two thirds, golden-yellow pilose on dorsal third.

Thorax: Scutum black with dorsomedial area almost uniformly grey pollinose with some metallic iridescence, with lateral yellow vitta and sublateral matte black vitta, black pilose except notopleuron yellowish pilose on anterior half and some scarcely distributed yellow hairs on dorsum, densely black pilose on lateral notopleuron and supra-alar area; postpronotum yellow, brownish anteriorly; notopleuron yellow continuing until scutellum, with postalar callus entirely yellow; scutellum yellow with dorsomedial broad defined dark macula reaching anterior margin, black pilose, with subscutellar fringe with black hairs. Pleuron mostly yellow, except katepisternum brownish ventrally and meron dark, entirely yellow pilose; metasternum pilose; calypter yellow basally and very blackened distally with long black hairs on margin; plumula yellow, long, about twice as long as subalare; halter yellow; spiracular fringes yellow.

Wing: Wing membrane infuscate, brown, entirely microtrichose. Alula microtrichose, broad, broader than costal cell and slightly narrower than cell BM.

Legs: Coxa and trochanter yellow, yellow pilose except metacoxa and metatrochanter black and yellow pilose; pro- and mesofemur yellow on basal half to third, black on distal half to two thirds; metafemur black, only dark yellowish at the very basal section; tibiae and tarsi black; femora, tibia and tarsi black pilose.

Abdomen: Figure 26 . Parallel-sided; tergum 3 weakly margined. Dorsum mainly black, black pilose dorsally and laterally except tergum 1 yellow pilose laterally and tergum 2 yellow pilose laterally on anterobasal half; tergum 1 black, yellow laterally; tergum 2 black with two mesolateral round yellow maculae, laterally extending forward to anterolateral tergal margin (like ‘golf club’-shaped spots), yellow lateral margin on anterior half; terga 3 and 4 black with narrow sinuate yellow fascia on anterior half of tergum, resembling result of union of two slightly concave maculae; tergum 5 black with two small narrow subtriangular yellow maculae; terga 2, 3, 4, and 5 with posterior shiny black fascia on posterior margin; sterna yellow, sterna 1 and 2 yellow pilose, everywhere else black pilose; genital segments brownish; male genitalia brown, as in Figure 149 .

Female: Similar to male except for normal sexual dimorphism and as follows: face yellow pilose ventrally, yellow pilose with some black hairs medially and black pilose dorsally; occiput pale pilose on ventral half, golden yellow pilose on dorsal half with some golden hairs ventrally and black dorsally on dorsal part; frons with anteromedial triangular black area extended posteromedially, lateral yellow areas converging posteriorly creating an inverted Y-shaped area ( Fig. 28 ); notopleuron mainly yellow pilose, black pilose on lateral margin; abdominal tergum 2 with narrow yellow fascia (similar to fascia on terga 3 and 4) narrowly interrupted medially and laterally extending forward to anterolateral tergal margin, with lateral margin yellow on anterior half; abdominal tergum 5 with two narrow, almost horizontal, yellow maculae, which may look like a fascia interrupted medially, extending anteriorly on lateral margin ( Fig. 25 ).

Variation: Some specimens have isolated black hairs (three or four hairs and never together as a tuft) on anterior anepimeron and posterior margin of anepisternum. Females are rather similar to the description of the holotype (see Wyatt, 1991: 161), but medial dark facial vitta varies from very dark to light brown although it is always visible. A few specimens also have some black hairs on anterior anepimeron and/or on posterior margin of anepisternum. Specimens may also have a continuous macula like a yellow fascia on abdominal tergum 2, with a narrow discontinuity not visible.

There are darker specimens with posterior anepisternum dark on anterior half, ranging from brown to black. Dark specimens usually have katepisternum darker ventrally and katatergum black posteriorly. Some of these dark individuals have yellow iridescence and yellow pollinosity on anepisternum and anepimeron; thus, they could look yellow. Dark individuals do not match with the description ‘ Pleurae with large continuously yellow area ’ as stated by Wyatt (1991: 161). This area is shown in Wyatt (1991: 168, fig. 1) by a stippled area.

Length (N = 5): Body, 8.2–10.1 (9.4) mm; wing, 7.8– 9.75 (8.3) mm.

Geographical distribution: New Guinea.

Ecology: Female holotype was collected ‘in logged forest’.

Differential diagnosis: Small, slender species with abdomen almost parallel-sided. Species with wing infuscated, scutellum yellow with triangular black macula reaching anterior margin, and legs dark brown except pro- and mesofemur yellow basally. Citrogramma robertsi has abdomen with very narrow yellow fasciae ( Figs 25, 26 ), and male frontal triangle yellow with posterior margin with a narrow black vitta ( Fig. 27 ), character not shared with other species like C. pendleburyi , C. vockerothi , C. circumdatum , C. hervebazini , and C. solomonense .

Remarks: Wyatt (1991) based his new species, C. robertsi , on a single female deposited in the BMNH. I provided here a complete description of the male, as several were found in other museum collections.

Holotype female deposited in The Natural History Museum, formerly British Museum (Natural History) (London, UK) and labelled: ‘ PAPUA NEW GUINEA: / Bulolo,/Gumi Logging Area / 9–V–1983 / H. Roberts ’ [handwritten] ‘HOLO–/TYPE’ [round, red] ‘ HOLO- TYPE ♀ of/ Citrogramma / robertsi n.sp. /det. N.P. Wyatt 19 89 ’.

Type locality: Papua New Guinea: Morobe Province, Bulolo District, Gumi Logging Area , 70°20′S, 146°42′E .

Material examined: Type material. Holotype, as above.

Nontype material. PAPUA NEW GUINEA: E. Highlands Prov., Mt Gahavisuka Prov. Park (NW of Goroka), Lipizuga Cr., c. 2200 m, 12–17.viii.1983, S. & P. Miller [3♂ 4♀, USNM]; Eastern Highlands District, no. 9, Kimi Creek Camp, NE slopes Mt Michael , 1980 m, 27.viii.1959, L.J. Brass, Coll. Sixth Archbold Exped. to Papua New Guinea [3♂, AMNH]; Morobe Distr., Mt Misim , 17.iii, Stevens ‘ Frank M. Hull Collection C.N.C. 1973’ [1♀, CNC]; Morobe Distr., Wau , 1400 m, 20.xii.1961, J. & J.H. Sedlacek [1♂ 2♀, BPBM];..., 16.vi.1961,... [1♀, BPBM]: 6 km W of Wau, Nami Creek , 1700 m, 10.vi.1962, J. Sedlacek [1♂, BPBM]; Morobe, Nami Creek , 10.vi.1962, J. & M. Sedlacek [1♀, BPBM];..., 10.vi.1962, Light trap,... [1♀, BPBM]; Okapa, 64 km S of Kainantu, 1800 m., 29.ix.1959, T . C. Maa [1♀, BPBM]; Eliptamin Valley, 1200–1350 m, 1–15.viii.1959, W.W. Brandt [2♂ 1♀, BPBM]; Daulo Pass area, 2500 m, 5.vii.1957, D.E. Hardy [1♀, BPBM]; Iongai, 10 km E of Mt Albert Edward, 1450 m, 7.xi.1965, J. Sedlacek [1♀, BPBM]; Mt Kaindi , 2350 m, v.1968, N.L.H. Krauss [1♀, BPBM]; Wau , 1200–1450 m, 18.vi.1968, N.L.H. Krauss [1♂, BPBM];..., vii.1968,... [1♂, BPBM]; Feramin, 150– 120 m, 23–31.v.1959, W.W. Brandt [1♂, BPBM]; NW Wisselmeren, Enarotadi, 14.vii–4.viii.1962, J. Sedlacek [1♂, BPBM]; Owen Stanley Range, Goilala, Bome, 1950 m, 24.ii–7.iii.1958, W.W. Brandt [1♂, BPBM] .

Figures

Figures 27–38. 27–28, Citrogramma robertsi: 27, dorsal view of male head; 28, dorsal view of female head. 29, Citrogramma hervebazini, dorsal view of male abdomen. 30, Citrogramma vockerothi, dorsal view of male abdomen. 31, Citrogramma solomonense, lateral view of male pleuron. 32, C. vockerothi, lateral view of male pleuron and head. 33–37, Citrogramma circumdatum: 33, dorsal view of male abdomen; 34, dorsal view of female abdomen; 35, lateral view of male pleuron; 36, dorsolateral view of female scutum and pleuron; 37, dorsal view of female head; 38, C. solomonense, lateral view of male head.

Figures 15–26. Dorsal view of abdomen. 15–16, Citrogramma bicornutum: 15, female; 16, male. 17, Citrogramma asombrosum, male. 18–19, Citrogramma quadratum: 18, male; 19, female. 20–21, Citrogramma arisanicum: 20, male; 21, female. 22, Citrogramma australe, male. 23–24, Citrogramma notiale: 22, female; 24, male. 25–26, Citrogramma robertsi: 25, female; 26, male.

Figures 145–150. Male genitalia. 145, Citrogramma matsumurai, left lateral view. 146, Citrogramma wyatti, left lateral view. 147–148, Citrogramma pennardsi: 147, left lateral view; 148, tergum 9 and surstyli, dorsal view. 149, Citrogramma robertsi, left lateral view. 150, Citrogramma quadratum, left lateral view.