(Figs 4, 5, 6A–D)
Material examined. Holotype: INDONESIA • ♂; Maluku, Kei Eil. [Kai Islands], Gn. [= Gunung, mountain] Daab; 1922; #89; identified Piestodactylus siebersi, paratype, by L. Chopard; H. C. Siebers leg. (MZB-ORTH10032).
Paratypes: INDONESIA • ♀; Indonesia, Maluku, Kei Eil. [Kai Islands], Gn. [= Gunung, mountain] Daab; 1922; #132; H. C. Siebers leg. (MNHN-EO-ENSIF1429) • 4♂; same information as holotype (MZB-ORTH10028, 10029, 10031, 10035) • 1♀; same information as holotype (MZB-ORTH10030) • 1♂; same locality and collector as holotype, #82 (MNHN-EO-ENSIF1438) • 1♂; same locality and collector as holotype, #79, molecular sample L74 (MNHNEO-ENSIF 1453) • 2♀; same locality and collector as holotype; #85 and #105 (MNHN-EO-ENSIF1439-1440).
Type locality. INDONESIA, Maluku, Kei Eil [Kai Islands].
Etymology. This species is named after its type locality, Kai Islands; noun in apposition.
Diagnosis. This new species is most similar to Macrobinthus kutini Robillard & Su, 2018 in male genitalia (shapes of pseudepiphallus and pseudepiphallic parameres) and FW venation, but differs by details of male genitalia (pseudepiphallic lophi more rounded, ventral lobe of pseudepiphallic parameres without long tapering anterior process), and by longer female FWs. It differs from Macrobinthus jharnae (Bhowmik, 1981) by the stout pseudepiphallus and shapes of pseudepiphallic parameres and pseudepiphallic lophi; and from Macrobinthus wilhelmsis Robillard & Dong, 2016 by male genitalia having pseudepiphallus with paired lophi at posterior apex. The female of the new species also differs from Macrobinthus newguineae (Bhowmik, 1981) and Macrobinthus songi Robillard & Dong, 2016 by slenderer and more elongated female copulatory papilla.
Description. Size medium for the genus (Fig. 4). Vertex and fastigium dark brown. Dorsum of head mostly dark brown, with five faint longitudinal pale bands (Fig. 5A); back of eyes with a yellow band. Scapes white, with brown patterns. Antennae orange brown. Fastigium verticis and frons dark brown (Fig. 5B); with faint whitish spots below antennae and eyes. Mouthparts brown and white, mandibles brown mottled white; clypeus white laterally and brown in the middle; maxillary palps with segments cream-coloured to pale brown, slightly darker at apices (Fig. 5B). Lateral parts of head mostly brown (Fig. 5C). Pronotum dorsal disk dark brown mottled with yellow, anterior margin straight; lateral lobes dark brown, darker than dorsal disk (Fig. 5C). Legs: FI–II light brown with brown spots; TI–II dark brown with a yellow ring; tarsomeres 1 and 3 of each leg yellow basally then brown; FIII brown finely mottled with yellow and dark brown, knees dark brown; TIII homogeneously dark brown. Abdomen brown. Cerci light brown with faint apical rings.
Male: FW reaching middle of third tergite. FW colouration (Fig. 5D): Dorsal field cells mostly brown, veins whitish or cream-coloured; M and R veins yellow brown. Lateral field cells brown, with ventral region more yellow brown; longitudinal veins brown with cross-veins cream-coloured. FW venation: 1A vein (file) slightly bisinuous. Harp narrow, with one main sinuous oblique vein. Mirror not differentiated from other cells of D alignment. Apical field including 2 short cell alignments; apex of dorsal field obliquely rounded. Lateral field with straight longitudinal vein, including Sc, without projection, and 5 more ventral veins.
Male genitalia (Figs 6A–C): Pseudepiphallus triangular, stout, with lophi setose dorsally and ventrally, more roundish with apices obtuse. Pseudepiphallic parameres large, trilobate; with a ventral lobe sclerotized and with posterior margin rounded, a lateral lobe oriented dorsally with obtuse apex, and a very small and stout basal lobe. Ectophallic apodemes slightly diverging anteriorly and long, barely surpassing beyond anterior margin of pseudepiphallic sclerite. Endophallic sclerite Y-shaped, comprising a long anterior region and a short median expansion with subacute apex and fairly elongated lateral arms posteriorly surpassing median expansion.
Female: FWs relatively long for the genus, reaching middle of fourth tergite, slightly overlapping. Cells of dorsal field dark brown, not translucent, with strong orange longitudinal veins and weak yellow or whitish transverse ones; with nine longitudinal veins on dorsal field and five on lateral field; 6th longitudinal vein from inner edge λ-shaped, with a bifurcation at mid-length; 7th vein fused to 8th vein at ⅔ of FW length. Dorsal field apex rounded, lateral field posterior margin curved. Ovipositor as long as FIII, apex slightly denticulate dorsally.
Female genitalia (Fig. 6D): Copulatory papilla roundly triangular; basal sclerite forming a semi-circular ring with a small basal plate; bent at apical third in lateral view; apex narrowed and rounded, slightly sclerotized.
Measurements. Table 1.