Amblypsilopus riuensis, Bickel, 2019

Bickel, Daniel J., 2019, The Amblypsilopus amnoni and megastoma groups in New Guinea (Diptera: Dolichopodidae: Sciapodinae), Israel Journal of Entomology (Oxford, England) 49 (2), pp. 195-214 : 210-211

Amblypsilopus riuensis n. sp.

( Figs 16, 17)

LSID: urn:lsid:zoobank.org:act:D0E3F2DF-B16D-482B-9C21-66856E33BA72 .

Etymology: The species is named after the Mt Riu type locality on Sudest Island.

Description: Male. Length 5.6 mm, wing 4.2× 1.1 mm ( Fig. 16).

Similar to A ibiscorum except as noted:

Thorax. Almost entirely yellow, except with shining metallic blue-green reflection on mesonotum, and metepimeron somewhat infuscated.

Legs. All coxae, trochanters, femora, tibiae, and basal tarsomeres yellow, with distal tarsomeres becoming infuscated, coxae with black setation; legs with short black vestiture; I: 5.7, 6.9, 11.3/2.2/21/distal tarsomeres missing; TI slightly bowed, with pale yellow cUrved posterior seta at ⅗ (MSSC) and withoUt whitish ventral pile along length, It 1 elongate, longer than to TI with group of 3 black ventral setae at very base (MSSC); It 5 missing; II: 5.8, 8.8, distal tarsomeres missing; III: 8.8, 14.9, 6.2/2.3/distal tarsomeres missing; setation similar; IIIt 1 also with pair short ventral setae near base.

Abdomen. Tergite 1 metallic blue green; tergites 2–7 mostly yellow, but with brown band along posterior fifth of each tergite 2–5, but wider and more metallic posterior band on tergite 4; sternite 8 dark brown; hypopygium ( Fig. 17) dark brown with yellow surstylus and cercus; epandrium tapering triangular; surstylus curved, digitiform aboUt ⅓× as long as epandriUm; cercUs elongate, with pale yellow hairs, with blade-like ventral arm arising near ⅖ and recUrved back towards cercal base, and cercus distally with mound bearing long hairs, and tapering with long apical hairs.

Female. Unknown.

Holotype: ♂ Papua New Guinea: Milne Bay Province, Sudest Island, Mt Riu [11°31'S 153°26'E], 250–350 m, 10.xi.1956, Fifth Archbold Expedition to New Guinea, L.J. Brass ( AMNH).

Remarks: Amblypsilopus riuensis is known only from Sudest Island, Milne Bay Province, Papua New Guinea. The thorax is almost entirely yellow, and the elongate cercus, with its blade-like ventral arm arising near mid-length and recurved back towards the cercal base cercus is diagnostic for this species.

The Amblypsilopus megastoma Group

Diagnosis: Head. Major head setae black; males with short black hair-like vertical seta on lateral slope of vertex (MSSC), female with strong vertical seta; proboscis pale yellow with labella on both sexes greatly extended and expanded, comprising two translucent white glabrous lips with pseudotracheae clearly visible externally; antennal pedicel with subapical coronal of short black setae and stronger dorsal seta; postpedicel subrectangular, with apical arista.

Thorax. Mostly yellow, shining with little pruinosity, but mesonotum with shining metallic blue reflections; setae black; 2 pairs of long ac, with short pair anteriormost, both sexes with 2 strong posterior dc and weak hair-like dc anteriad; median scutellar setae strong, laterals absent.

Legs. All coxae and legs mostly yellow; legs mostly bare of major setae; TI with short pale curved posterior seta at 9/ 10, just before apex (MSSC); It 1 longer than TI in both sexes; It 5 black, flattened and expanded into apical pinnate flag (MSSC).

Wings. Hyaline, elongate; vein M 1 in right-angled arch M 1 to approach R 4+5 and join costa anterior to wing apex; dm–cu straight,

Abdomen. Tergites mostly yellow; epandrium subrectangular; surstylus as short projecting arm; cercus flagelliform.

Remarks: The Amblypsilopus megastoma group is known from two species ( ialibu n. sp. and megastoma n. sp.) in Papua New Guinea, one from 700–800 m in the Star Mountains and females from coastal lowlands near Madang, and the second species above 2000 m from Southern Highlands and Oro provinces.

Both sexes have the labella enlarged into yellow translucent plates (narrower in females) with clearly visible pseudotracheae. Males of the two known species have leg I tarsomere 5 modified into an apical black pinnate flag. Both sexes have a yellow clypeus and the basitarsus of leg I longer than tibia I. Also, as in the amnoni group, known females have the some anterior dc setae reduced to fine hairs, normally a character only found as a male secondary sexual character in Sciapodinae .