Pseudagrion acutidens, Seehausen & Kalkman & Bedjanič, 2025

Pseudagrion acutidens sp. nov.

Figures: 5 (habitus holotype ♂); 6–8 (S9–10, caudal appendages holotype ♂); 9 (head holotype ♂); 10 (pronotum holotype ♂); 11 (habitus paratype ♀); 12 (head paratype ♀); 13 (pronotum paratype ♀); 14 (S9–10, ovipositor paratype ♀); 79 (head ♂); 96 (pterothorax ♂); 113a, b (abdomen ♂); 130a–c (caudal appendages ♂); 147–151 (field photos ♂).

Holotype: ♂, acq. v.1933, Tobelo , Halmahera Island, North Maluku, Indonesia, approximately 1.724°N, 127.997°E, van Diejen leg., no. 1519102. Deposited at Naturalis Biodiversity Center Leiden, the Netherlands. GoogleMaps

Paratypes (4♂♂, 2♀♀): 2♂♂, 1♀, acq. v.1933, Tobelo , Halmahera Island, North Maluku, Indonesia, approximately 1.724°N, 127.997°E, van Diejen leg., RMNH, no. 1519101, 1519102 GoogleMaps ;— 1♂, 1♀, 8.vii.1985, Wayaua , rivulet, edge of logged forest, Bacan Island, North Maluku, Indonesia, approximately - 0.741°N, 127.641°E, F.G. Rozendaal leg., RMNH, no. 1519079 GoogleMaps ;— 1♂, 1.viii.1997, primary rainforest 9 km of logging company camp Chucumara , Morotai Island, North Maluku, Indonesia, alt. 400–480 m, R. Verovnik leg, MB .

Etymology: The name refers to the inferior lobe of the male cercus, which has a large tooth-like medially pointed projection, clearly visible in dorsal view.

Remarks: Further specimens from the islands of Halmahera, Bacan, Buru, and Obi were discovered among unidentified material at the RMNH by V.J. Kalkman just prior to submission of the manuscript. For this reason we have not included them in the type series.

Description of holotype male

Head ( Fig. 9, also compare Fig. 79): Labium, mandibles, genae, labrum, anteclypeus and postclypeus yellow; antefrons and postfrons yellow, with posterior margin of postfrons washed out reddish, sharply separated from black vertex around level of anterior margin of lateral ocelli; a yellow-orange centre marking at vertex expands towards occipital bar; median ocellus with black spot posteriorly; occipital bar reduced to a small orange-reddish stripe in centre; triangular postocular spots orange-reddish, bordered by black; rear of head black, but pale along the eye margins; base and scape of antennae yellow, pedicel ochre-brownish, rest of antennae lacking.

Thorax ( Figs 5, 10, also compare Fig. 96): Anterior lobe of pronotum yellowish, with anterior margin black; the yellow colour projecting in centre as semi-circle towards middle lobe; middle pronotal lobe otherwise black, with a centrally divided yellow-orange patch in the middle, and on each side a large yellow-orange patch dorsolaterally; propleuron black above, yellow-orange below and to rear; posterior lobe yellow-orange; apical edge of posterior lobe convex. Pterothorax orange-reddish; middorsal carina black; moderately broad black humeral stripe, slightly widened at posterior third before peaked towards posterior margin of pterothorax; interpleural suture black with a black spot anteriorly; posterior half of metapleural suture black; mesinfraepisternum with black diagonal marking, continuing the black humeral stripe; venter pale, covered with whitish pruinosity. Coxae and legs pale orange-ochre; outer side of femur with a washed-out blackish stripe, covering almost complete femur in foreleg, almost complete posterior half of femur in midleg, and posterior quarter of femur in hind leg; tibiae blackish along the black spines; tarsi and tarsal claws orange-ochre, washed-out blackish along waists.

Wings ( Fig. 5): Membrane hyaline, slightly tinged yellowish-brown; veins brown to black; 16.0–16.5 px in forewing; 14.5–15.0 px in hindwing; Pt reddish-brown, overlying one cell.

Abdomen ( Figs 5–7, also compare Figs 113a, b): S1 orange-reddish, dorsally with a black quadrangular patch covering anterior two-thirds of segment, posterior margin black; S2 orange-reddish, dorsally with acute mushroom-like black marking at posterior third, and triangular black patch at anterior margin; both black markings almost connected by thin black middorsal stripe; S3–8 dorsally black, expanded to lateral half of segment; pale yellowish basal annulus; laterally and ventrally pale yellowish-orange; S9 with anterior half laterally and dorsally orange-reddish; posterior half of S9 black, with its anterior margin somewhat serrated with incomplete middorsal stripe; S10 orange-reddish, dorsally with broad black “x”-like marking; black colour of anterior and posterior margin expanded laterally.

Caudal appendages ( Figs 6–8, also compare Figs 130a–c): Cercus laterally washed-out brownish, slightly shorter than S10; in lateral view cercus subrectangular, with inter-lobe notch centrally placed at the apex; in dorsal view apex of superior lobe of cercus rounded and curved in; inferior lobe expanded inwards, subtriangular, apex of expanded part blackish and tooth-like, curved towards body; paraproct blackish at base, apex orange-brownish; slightly longer than half of cercus; viewed laterally subtriangular and tapered, with apex rounded; viewed dorsally paraproct broadly rounded, concave bowl-like, with blackish tubercular medial edge.

Measurements (mm): Total length (with appendages) 43.2; abdomen length (without appendages) 36.1; hindwing 23.6; forewing 25.2; Pt in forewing 0.8; cercus 0.5.

Variation in paratype males

Head: All males have a black spot at centre of posterior margin of postclypeus (as in Figs 79, 148; not visible in Fig. 9 of the holotype because of dirt); the occipital bar is completely black in two males.

Thorax: The males from Morotai and Bacan have the metapleural suture almost completely covered by a black stripe.

Wings: 14.5–17.5 px in forewing; 13.5–15.0 px in hindwing.

Abdomen: Two males have the triangular black patch at anterior margin of S2 reduced; the male from Morotai has a complete thin black middorsal stripe on S2 (as in Fig. 147); the male from Bacan has S8 dorsally black, but with two elongate triangular reddish patches at anterior third, each situated dorsolaterally, and about as long as one-third of S8; one male has S9 with a black dot each lateral of the incomplete middorsal stripe.

Measurements (mm): Total length (with appendages) 42.3–45.3; abdomen length (without appendages) 35.7– 38.0; hindwing 23.3–24.2; forewing 25.0–25.6; Pt in forewing 0.8–0.9; cercus 0.5.

Description of female paratypes

Head ( Fig. 12): Labium, mandibles, genae, labrum, anteclypeus and postclypeus yellow-orange; postclypeus with at least a blackish dot at centre of posterior margin, and an elongated blackish spot at each side, but may likewise be almost completely dark; antefrons and postfrons yellow-orange, with a black elongated patch in centre; yellow-orange colour of postfrons sharply separated from black vertex around level of lateral ocelli; median ocellus with a black spot posteriorly; lateral ocelli largely surrounded by black, less distinct or lacking at their anterior margins; triangular postocular spots orange-reddish, broadly bordered by black; rear of head black, but pale along the eye margins; base and scape of antennae orange-ochre, following segments brownish.

Thorax ( Figs 11, 13): Pronotum with anterior lobe pale yellowish, its anterior margin black; middle pronotal lobe black with a centrally divided yellowish patch in the middle, and on either side a large yellowish patch dorsolaterally; propleuron black above, pale yellowish below and to rear; posterior lobe of pronotum yellow-brownish; apical edge of posterior lobe convex, bearing two dark horns directed towards head, approximately reaching the centre of the middle lobe. Pterothorax orange; middorsal carina black; moderately broad black humeral stripe, slightly widened in posterior third before peaking towards posterior margin of pterothorax; interpleural suture darkened with blackish spot anteriorly; metapleural suture at least with black elongated patch posteriorly, but may be almost completely blackish; mesinfraepisternum with black diagonal marking, continuing the black humeral stripe; venter of pterothorax pale yellowish, may be covered with whitish pruinosity. Coxae and legs pale yellow-ochre; outer side of femur with a washed-out blackish stripe along posterior two-thirds in foreleg, reduced to posterior half in midleg, and posterior quarter in hindleg; tibiae blackish along the black spines; tarsi and tarsal claws yellow-ochre, washed-out blackish along waists.

Wings ( Fig. 11): Membrane hyaline, may be slightly tinged yellowish-brown; veins brown to black; 17.5–18.0 px in forewing; 14.5–16.5 px in hindwings; Pt ochre, overlying one cell.

Abdomen ( Figs 11, 14): S1 yellow-orange, dorsum black; S2 yellow-orange, with black dorsal marking which is expanded laterally at posterior third, and may also be widened at anterior margin; S3–8 dorsally black, expanded to lateral half of segment, pale yellowish basal annulus; laterally and ventrally pale yellowish; S9–10 dorsally black, expanded to lateral along posterior and anterior margin; laterally and ventrally pale yellowish. Cercus dark, as long as half of S10; paraproct dark, rounded laterally; ovipositor pale yellowish, its apex not reaching to posterior end of S10; bearing two yellow-brownish styles reaching beyond S10; inferior edge of ovipositor bearing several very small teeth.

Measurements (mm): Total length (with appendages) 41.6–42.0; abdomen length (without appendages) 33.8– 34.5; hindwing 25.1–25.3; forewing 26.6–26.8; Pt in forewing 0.8–1.0.

Diagnosis

Pseudagrion acutidens overlaps in range on Halmahera with P. halmaherae described below, and on Buru with P. crocops and P. ustum . However, males of P. acutidens can easily be separated from all congeners west of Lydekker’s Line by the large medially projecting tooth on the cercus ( Figs 7–8, 130b, c, 149). Pseudagrion ustum has a tooth of similar size on the cercus, but in that species the tooth is projecting upward ( Figs 146a–c). Furthermore P. halmaherae has a broad humeral stripe in both sexes ( Figs 33, 39, 103), whereas the humeral stripe is narrower in P. acutidens ( Figs 5, 11, 96, 147–148, 150–151). Furthermore both species differ in both sexes in the shape of the postocular spots, which are more rectangular and narrower, with a somewhat serrated posterior margin in P. halmaherae (compare Figs 9, 12, 37, 40, 79, 86).

Distribution

This species is restricted to the northern Maluku Islands. Records are available from Morotai, Halmahera, Obi, Bacan, and Buru ( Fig. 3).