Citrogramma quadratum, Mengual, 2012

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 : 157-158

CITROGRAMMA QUADRATUM MENGUAL SP. NOV.

Description

Male: Head: Face with facial tubercle, gradually sloping dorsally, more abrupt ventrally, yellow with medial indefinite dark vitta, from oral apex to antennal basis, narrower than yellow lateral areas of face, mainly dark brown pilose, yellow pilose on ventral portion, white pollinose laterally and ventrally; gena yellow, mainly yellow pilose with a few brown hairs on genal suture, white pollinose posteriorly; holoptic; lunule dark, orangish medially; frontal triangle yellow with anteromedial black triangular area pointed posteriorly, black pilose; vertical triangle black, black pilose; ocelli reddish; antenna dark brown, black pilose on scape and pedicel; basoflagellomere dark, brownish ventrally; arista black; occiput black, silver pollinose, yellow pilose with some black hairs dorsally.

Thorax: Scutum dark, golden-grey pollinose with three metallic bluish clearly defined vittae (median vitta narrower), with lateral yellow vitta, black and yellow pilose except notopleuron yellow pilose anteromedially, densely black pilose on ventral notopleuron and supra-alar area; postpronotum yellow; notopleuron yellow, brownish ventrally, continuing until scutellum with postalar callus entirely yellow; scutellum yellow with dorsomedial broad brownish macula reaching anterior margin, black pilose, complete subscutellar fringe of dark brown hairs. Pleuron mostly yellow, except katepisternum black ventrally, meron dark, anepimeron dark, anterior anepisternum blackish posteriorly and posterior anepisternum black on anterior half (brownish in holotype male), entirely yellow pilose, yellowish white pollinose; metasternum pilose; calypter yellow, darkened basally and distally with dark hairs on margin; plumula yellow; halter yellow; spiracular fringes yellow.

Wing: Wing membrane yellowish, entirely microtrichose. Alula microtrichose, broad, broader than cell BM.

Legs: Coxa yellow, trochanter brownish, yellow and black pilose; pro- and mesofemur brownish, yellow basally, mainly black pilose, yellow hairs basally; pro- and mesotibia brown or darker; pro- and mesotarsus dark brown, black pilose; metaleg dark brown or black, black pilose.

Abdomen: Figure 18 . Parallel-sided, narrowed posteriorly; terga 4 and 5 margined. Dorsum mainly black, black pilose dorsally and laterally except tergum 1 yellow pilose laterally and tergum 2 yellow pilose laterally on anterobasal quarter and yellow pilose on maculae; tergum 1 black, yellow laterally; tergum 2 dark brown-black with two mesolateral broad, square yellow maculae, yellow lateral margin on anterior half; tergum 3 blackish with broad yellow fascia (about third to half of abdomen length) with anterior margin pointed forward medially, with anterior narrow black fascia; tergum 4 blackish with yellow fascia narrower than fascia on 3, with anterior narrow black fascia; tergum 5 black with two small subtriangular yellow maculae; anterior sterna yellow, yellow pilose, sternum 4 black pilose, 5 and posterior sterna darker, brown, black pilose; genital segments yellowish in part; male genitalia as in Figure 150 .

Female: Similar to male except: face yellow with medial broad black vitta, dark pilose, yellow pilose on ventral section; gena yellow, yellow pilose; frons yellow with medial broad black vitta narrowing dorsally and reaching ocellar triangle, black laterally on eye margin on dorsal half; occiput mainly yellow pilose, black pilose on dorsal third; subscutellar fringe less dense; pro- and mesofemur darker, brown. Abdominal pattern different ( Fig. 19 ): dorsum mainly black, black pilose dorsally and laterally except tergum 1 yellow pilose laterally and tergum 2 yellow pilose laterally on anterobasal quarter; tergum 1 black, yellow laterally; tergum 2 black with two mesolateral broad yellow maculae joined medially forming a broad yellow fascia narrowed laterally, occupying more than half of tergum, reaching lateral margin anteriorly with a medial black macula on anterior margin of tergum 2; tergum 3 black with narrow yellow fascia (about fifth of tergum length) expanded medially anterior and posteriorly, occupying half of tergum length; tergum 4 similar, black with narrow yellow fascia (about fifth of tergum length) expanded medially anteriorly and posteriorly but less, occupying one third of tergum length; tergum 5 black with two lateral triangular yellow maculae pointed anteriorly; sterna yellow, mainly yellow pilose with black hairs posteriorly.

Variation: The pleural pattern varies in males. The male deposited at RMNH is lighter than the other specimens, and it has anepimeron yellow and the black areas of anepisternum look brownish, not as clear as in the other males. The two individuals in CNC are also a bit lighter than the specimens in BPBM, but not like the male in RMNH.

The colour of anepimeron is variable, from yellow to completely black, and it is probably because males with yellowish or yellow and black anepimeron look like immature adults. Some specimens have scutum without bluish vittae as a result of preservation condition. Colour of pro- and mesofemur is also variable amongst specimens.

Length (N = 5): Body, 8.7–9.5 (9.1) mm; wing, 8.2–9.2 (8.7) mm.

Geographical distribution: New Guinea.

Etymology: The specific epithet is derived from the Latin quadratus meaning square, four-cornered ( Brown, 1956: 746), and refers to the square yellow macula that this species has on the second abdominal tergum. Species epithet to be treated as an adjective.

Differential diagnosis: Species very distinct with two unusual square maculae on abdominal tergum 2 in males ( Fig. 18 ), and with medially broadened yellow fasciae in females ( Fig. 19 ). Citrogramma quadratum can be related to other slender species such as C. robertsi or C. notiale by external morphology, but is easy distinguishable by the characters mentioned above.

Remarks: Although it is the specimen with lightest pleural pattern, the male in RMNH is the most perfect. Metallic pollinosity can be easily seen on this specimen, and antennae and legs are entire, undamaged.

Holotype male deposited in the Bernice P. Bishop Museum (Honolulu, Hawaii, USA) and labelled: ‘ Nami Ck / 10.VI.63 ’ [handwritten] ‘J. &M. Sedlacek/ Collectors/BISHOP’ ‘ HOLOTYPE / Citrogramma / quadratum /det. X. Mengual 20 09 ’ [red, second and third lines handwritten].

Type locality: Papua New Guinea: Morobe Province, Wau, Nami Creek , 70°20′S, 146°42′E .

Material examined: Type material. Holotype, as above. Paratypes. PAPUA NEW GUINEA: Morobe Province, Mt Misim, 17.iii, Stevens [2♂, CNC]; 16 km SW of Wau, Mt Kaindi , 2300 m, 8–9.vi.1962, J. Sedlacek [1♂, BPBM]; (NE) 6 km of Wau , Nami Creek , 1700 m, 10.vi.1962, J. & M. Sedlacek [1♀, BPBM]; Nami Creek , 10.vi.1962, J. & M. Sedlacek [1♀, BPBM]; *Tresobul*, 2200 m, J. & M. Sedlacek [1♀, BPBM]; NE, Daulo Pass, 2500 m, 2.v.1959, C.D. Michener [1♀, BPBM]; INDONESIA: Papua Province, Iebele Camp, Neth. Ind.-American New Guinea Exped., 2250 m, 3.xii.1938, L.J. Toxopeus [1♂, RMNH] .

Figures

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.