Citrogramma distinctum, Thompson, 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 : 139-140

CITROGRAMMA DISTINCTUM THOMPSON SP. NOV.

Description

Male: Head: Face with low facial tubercle, gradually sloping dorsally, more abrupt ventrally, with oral apex slightly more prominent than antennal base, entirely yellow, black pilose; gena yellow, dark pilose; lunule yellow; holoptic; frontal triangle yellow with very narrow posterior black vitta on eye margin, black pilose; vertical triangle black, black pilose, golden pollinose; ocelli reddish; antenna orangish brown, black pilose on scape and pedicel; basoflagellomere orangish, dark dorsally; arista dark; occiput black, silver pollinose, pale pilose on ventral half, yellow pilose medially and dark pilose on dorsal third.

Thorax: Scutum black with dorsomedial area almost uniformly grey pollinose with some metallic iridescence, with a lateral yellow vitta, black pilose except notopleuron yellowish pilose on anteromedial half, densely black pilose on lateral notopleuron and supraalar area; postpronotum yellow, brownish anteriorly; notopleuron yellow continuing until scutellum, with postalar callus entirely yellow; scutellum yellow with dorsomedial broad dark brown macula, black pilose, with a subscutellar fringe with black hairs, bare in middle. Pleuron mostly yellow, except posterior anepisternum black on anteroventral third, katepisternum black with dorsal yellow macula, meron black, posterior anepimeron black, katatergum black posteriorly, grey pollinose ventrally, mainly yellow pilose, except anterior anepimeron black pilose with little yellow hairs dorsally, anepisternum black pilose on posterior and dorsal sections; metasternum pilose; ventral calypter yellow with black hairs on margin, dorsal calypter yellow, darkened anterodistally; plumula yellow, long; halter orangish; spiracular fringes yellow.

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

Legs: Pro- and mesocoxa and trochanter black, metacoxa and trochanter brownish; the rest of the legs black, except pro- and mesofemur yellow brownish on distal quarter and third respectively, and pro- and mesotibia dark brown or black, brown pollinose. Legs black pilose, tarsi golden pilose ventrolaterally.

Abdomen: See Figure 51 . Parallel-sided, terga 2, 3, and 4 margined. Dorsum mainly black, black pilose dorsally and laterally except tergum 1 yellow pilose anterolaterally; tergum 1 black with a lateral yellow macula; tergum 2 black with two mesolateral oblique yellow maculae, extending forward laterally to anterolateral tergal margin and broader mesomedially, yellow lateral margin on anterior quarter to third; terga 3 and 4 black with medial broad yellow fascia, less than third of tergum length, extending anterolaterally not reaching lateral margin; tergum 5 similar to 3 and 4 with narrower fascia; sterna yellow, yellow pilose on sterna 1 and 2, black pilose on the rest; male genitalia as in Figure 142 .

Female: See description of females given below under the C. schlingeri species group.

Length (N = 1): Body, 9.5 mm; wing, 8.5 mm.

Geographical distribution: New Guinea.

Etymology: The specific epithet is derived from the Latin distinctus meaning separate, different ( Brown, 1956: 274), and refers to the distinctness of the species although it is difficult to distinguish from C. schlingeri and C. triton using external morphological characters. Species epithet to be treated as an adjective.

Differential diagnosis: Species with entirely yellow face, gena yellow, broad frontal triangle (eye angle more than 90°) with a narrow black fascia on eye margin, costal cell darker than the rest of the wing membrane (except stigma), brown macula on scutellum and legs almost entirely black. As mentioned, species difficult to distinguish from others in its group, like C. schlingeri or C. triton ; only male genitalia are different. Citrogramma pintada and C. pinyton are very similar and they probably belong to the same species group, but these have anepisternum yellow.

Remarks: Thompson studied Citrogramma material in AMNH during his doctoral research many years ago. He found two different new species, C. schlingeri and C. distinctum , but never published them. When this revisionary work was started, he kindly offered this material to be included and new studied material was included. The male genitalia of C. distinctum are clearly different from the genitalia of C. schlingeri and C. triton , but there are no external morphological characters that can be used to distinguish them. Females of this species group are described together. Probably they are all a sympatric cryptic species complex, occurring in the same geographical area.

Holotype male deposited in the American Museum of Natural History (New York City, New York, USA) and labelled: ‘Mt Dayman/Maneau Range/ 2230 m N.SlopeNo.4/ June 1–7 –1953 /Papua, New Guinea’ ‘Geoffrey M. Tate/Collector’ ‘ HOLOTYPE / Citrogramma / distinctum /det. X. Mengual 20 09 ’ [red, second and third lines handwritten].

Type locality: Papua New Guinea: Northern Province (also known as Oro Province), Ijivitari District, Mount Dayman , 9°50′S, 149°16′E .

Material examined: Type material. Holotype, as above.

Figures

Figures 51–62. 51–52, Citrogramma schlingeri: 51, dorsal view of male abdomen; 52, dorsal view of female abdomen. 53, Citrogramma flavigenum, dorsal view of male abdomen. 54–55, Citrogramma sp. 1: 54, dorsal view of female abdomen; 55, wing. 56, C. flavigenum, dorsal view of male head. 57–60, Citrogramma luteopleurum: 57, dorsal view of female head; 58, dorsal view of male head and lateral view of scutum; 59, dorsal view of male abdomen; 60, dorsal view of female abdomen. 61–62, Citrogramma pintada: 61, dorsal view of male abdomen; 62, dorsal view of female abdomen.

Figures 140–144. Male genitalia. 140, Citrogramma bicornutum (from Vockeroth, 1969): a, left lateral view; b, superior lobe, lateral, outline only; c, sternum 9, superior lobes and aedeagal base, ventral view; d, right surstylus, lateral view. 141, Citrogramma schlingeri, left lateral view. 142, Citrogramma distinctum, left lateral view. 143, Citrogramma triton, left lateral view. 144, Citrogramma frederici, left lateral view.