Ischiodon astales, Mengual, Ximo, 2018

Mengual, Ximo, 2018, A new species of Ischiodon Sack (Diptera, Syrphidae) from Madagascar, African Invertebrates 59 (1), pp. 55-73 : 56-58

Ischiodon astales sp. n. Figures 2, 3 A–D, 4

Differential diagnosis.

Females and males of this new species do not have a calcar on the metatrochanter and they are easy to distinguish from other species since the two broad, yellow maculae on tergite 2 do not reach the lateral margins (Figs 2A, C, 3A, C). Moreover, males of I. astales sp. n. have symmetrical claws on the fore leg, the same as males of I. scutellaris .

Description.

Male: Head (Fig. 2A, B): Face with distinct facial tubercle, entirely yellow, yellow pilose; gena yellow with two small black macula at eye margin; lunule yellow; frons yellow, yellow pilose; vertical triangle black; antenna yellow, black pilose, basoflagellomere orange, darker dorsally; arista orange-yellow, bare; eye bare; occiput black, white pollinose and white pilose on ventral 1/2, yellow pollinose and yellow pilose on dorsal 1/2.

Thorax (Fig. 2A, C): Scutum shiny black, with long yellow pile; postpronotum paler, brownish, bare; notopleuron and supra-alar area yellow; postalar callus darker, brownish; scutellum yellow with medial area brownish, yellow pilose, subscutellar fringe yellow. Pleuron black, except posterior anepisternum yellow on posterior 1/2 and katepisternum with a dorsal yellow macula, yellow pilose; katepisternal pile patches separated; metaepisternum bare; metasternum bare; postmetacoxal bridge incomplete; calypter yellow, yellow pilose; plumula long, pale; halter pedicel and capitulum yellow; posterior spiracular fringes yellow. Wing: hyaline, bare on basal 1/2 and with sparse and irregularly scattered microtrichia on apical 1/2; alula mostly bare, with a few microtrichia posteriorly. Legs: fore and mid legs yellow with femora slightly more orange, coxae black and basal 1/2 of trochanters dark, entirely yellow pilose; hind leg with black coxae and basal part of trochanter dark; yellow metafemur with an almost imperceptible brown area on the apical 1/2, and metatibia slightly darker (dark yellow) on apical 1/2, black and yellow pilose.

Abdomen (Fig. 2A, C): Parallel-sided, with lateral margin from apical 1/2 of tergite 2 to tergite 5. Tergite 1 black, except yellow on lateral margins, yellow pilose; tergite 2 black, paler medially on posterior margin, with two large, rounded yellow maculae that do not reach lateral margins, yellow pilose, with short black pile on posterior margin; tergite 3 black on basal 1/2 becoming orange or brownish on posterior 1/2, with a medial yellow fascia that does not reach the lateral margins, with scattered, short, black pile; tergite 4 brownish-orange with a medial yellow fascia, black pilose except on the yellow fascia; tergite 5 brownish-orange, black pilose. Sternite 1 yellow; sternite 2 yellow with a medial, round, black macula; sterna 3 and 4 yellow becoming darker (brownish orange) towards genitalia; all sterna with yellow pile. Male genitalia: large, brownish-orange, as in Fig. 2E, F.

Female: Similar to male except for normal sexual dimorphism and as follows: frons black on dorsal 1/3, yellow on ventral 2/3 with a variable medial brownish orange vitta.

Variation: Due to the small number of specimens, one must expect variability in the coloration of the abdomen, legs and female frons, as in other Ischiodon species.

Length (N=4): Body, 10.0 mm (9.0-12.0 mm); wing, 7.7 mm (7.5-8.0 mm).

Geographical distribution.

Species known from the southern regions of Atsimo-Andrefana and Anosy, part of the former Toliara Province, Madagascar (Fig. 4; see Suppl. material 1: Table S1).

Etymology.

The specific epithet is derived from the Greek astales meaning unarmed, unclad ( Brown 1956: 122). Species epithet is to be treated as an adjective.

Type locality.

Madagascar: Atsimo-Andrefana Region, Mikea forest, NW of Manombo, 22°54.22'S, 43°28.53'E.

Material examined.

Type material. Holotype, male, pinned with genitalia in microvial, deposited in the CAS and labelled: "MADAGASCAR, Tulear // Province, Mikea Forest, // NW of Manombo, el 30 m, // 17 - 27 July 2003" " 22°54.22'S, 43°28.53'E // coll: M. Irwin, R. Harin’Hala // California Acad of Sciencies // malaise trap - in deciduous // dry forest MA-02-18A-62" "CASENT // 2210258" "HOLOTYPE // Ischiodon // astales // Det. X. Mengual 2017" [red]. Paratypes: Madagascar: Atsimo-Andrefana Region, Mikea Forest, NW of Manombo, 37 m., -22.91333°, 43.48217°, 12-20.xi.2001, M. Irwin, R. Harin’Hala [1♀, ZFMK; CASENT 2210121]; Atsimo-Andrefana Region, Zombitse-Vohibasia National Park, near ANGAP Office, 840 m., -22.8865°, 44.69217°, 31. x– 16.xi.2002, R. Harin’Hala [1♀, CSCA; ZFMK-DIP-00026782]; Anosy Region, Berenty Special Reserve, 8 km NW Amboasary, 85 m., -25.00667°, 46.30333°, 26. x– 2.xi.2002, M. Irwin, F. Parker, R. Harin’Hala [1♀, ZFMK; CASENT 2210162]; Anosy Region, Andohahela National Park, Ihazofotsy Parcelle III, 80 m., -24.83083°, 46.53617°, 23-30.xi.2003, M. Irwin, F. Parker, R. Harin’Hala [1♀, CAS; CASENT 2210150].

Remarks.

All specimens of this new species were collected using Malaise traps in different habitats. The male holotype was collected in a deciduous dry forest, while females CASENT 2210150 and CASENT 2210121 were collected in dry spiny forests and the female CASENT 2210162 in a gallery forest. On the other hand, the female ZFMK-DIP-00026782 was collected at a relative high altitude compared with the other specimens.