Leptanilla acherontia, Griebenow, 2024

Griebenow, Zachary, 2024, Systematic revision of the ant subfamily Leptanillinae (Hymenoptera, Formicidae), ZooKeys 1189, pp. 83-184 : 83

Leptanilla acherontia sp. nov.

Figs 9A-C , 10

Type material.

Holotype. Kenya - Kakamega • 1 worker; Kakamega Forest, Isecheno; 00.24°N, 34.85°E; 6 Nov. 2002; 1550m a.s.l.; W. Okeka leg.; equatorial rainforest, sifted litter in soil under Morus mesozygia ; CASENT0842720; UCDC Paratype. Kenya - Kakamega • 1 worker; same data as for holotype; CASENT0178284; LACM.

Other material examined.

Kenya - Kakamega • 1 worker; same data as for holotype; CASENT0842721; UCDC .

Measurements (mm) and indices.

Holotype: HW = 0.22; HL = 0.29; ML = 0.11; SL = 0.13; WL = N/A; PrW = 0.139; MW = 0.12; PTL = 0.11; PTH = N/A; PTW = 0.10; PPW = 0.11; TW4 = 0.21; CI = 75; SI = 62; MI = 52; PPI = 128.09; TI1 = 54.81. Other material examined: HW = 0.21; HL = 0.28; ML = 0.11; SL = 0.12; WL = 0.37; PrW = 0.13; MW = 0.11; PTL = 0.10; PTW = 0.09; PPL = 0.09; PPW = 0.10; TW4 = 0.20; CI = 75; SI = 58; MI = 55; PPI = 113; TI1 = 47.

Description.

Lateral margins of cranium subparallel. Occipital carina indistinct. Frontoclypeal process absent; frontoclypeal margin with median portion slightly raised, entire. Mandibles short relative to head. Three teeth present on mandible; apical and subapical teeth entire, intermediate tooth shallowly bifid (Fig. 10 ); irregular denticles interposed between all three teeth. Large, tapering basal seta absent from mandible; subapical tapering seta present. Scape short, not reaching cranial vertex at rest, somewhat expanded towards apex. Pedicel length distinctly greater than that of basal flagellomere. Flagellum submoniliform; length of basal flagellomere distinctly less than that of distal antennomeres; apical flagellomere 2 × longer than subapical flagellomere. In dorsal view, pronotal margins moderately convex, pronotal width only slightly greater than mesonotal width. Pronotal dorsum planar, not elevated above dorsal mesonotal vertex. Lateral margins of mesonotum and metapectal-propodeal complex subparallel in dorsal view; mesonotum not constricted anteriorly. Meso-metapleural suture absent dorsally; pleural portion visible as sinuate signum in oblique anterior view. Propodeum convex in profile view; propodeal declivity vertical and linear; posterolateral corners of propodeum rounded. Tarsomeres broader than long. Meso- and metatibial spur formula 1b,2(1b,1p). Anterior margin of petiole linear in dorsal view. Length and breadth of abdominal segment II subequal, distinct dorsal node present; margins parallel in dorsal view; subpetiolar process absent. Lengths of abdominal segments II-III subequal. Abdominal segment III slightly broader than long in dorsal view. Breadth of abdominal segment III approximately half that of abdominal segment IV in dorsal view (TI1 = 47-54). Abdominal tergites IV-VII visible in posterodorsal view. Anteroposterior length of abdominal tergite IV twice anteroposterior length of abdominal tergite V in dorsal view. Anteroposterior lengths of abdominal tergites V-VI subequal; anteroposterior length of abdominal tergite VII much less than that of abdominal tergite VI. Sculpture largely absent. Vestiture consisting of short subdecumbent setae, longer and more abundant on gaster than on remainder of soma. Coloration yellowish.

Etymology.

The specific epithet refers to Acheron, a subterranean river in Greek mythology, continuing a theme established by the specific epithets of the related Iberian species Leptanilla charonea and Leptanilla plutonia López, Martínez & Barandica, 1994. The gender is feminine.

Remarks.

Leptanilla acherontia sp. nov. most closely resembles Leptanilla revelierii Emery, 1870, Leptanilla kubotai Baroni Urbani, 1977, and Leptanilla okinawensis Terayama, 2013, with three mandibular teeth and a linear clypeal margin. Abdominal tergite V is proportionally longer in dorsal view in L. acherontia than L. revelierii , while L. acherontia differs from L. kubotai and L. okinawensis in pedicel shape and larger body size, respectively. Based on consultation of AntWeb images (https://www.antweb.org), Leptanilla UG01, known only from equatorial rainforest in Kibale National Park, Uganda, is almost certainly conspecific with L. acherontia .

With Leptanilla boltoni Baroni Urbani, L. acherontia is one of only two described Afrotropical Leptanilla species for which the worker caste is known. Phylogenomic inference indicates that Leptanilla zhg-ke02 may represent the male of L. acherontia (pers. obs.), but further sampling of sympatric Leptanilla would be required for this association to be decisive. The type locality of L. acherontia is situated in perhumid equatorial rainforest, contrasting with the semi-arid provenance of Leptanilla zhg-ke01 and other Afrotropical and Western Palaearctic Leptanilla . It is unclear to what degree climatic conditions dictate the distributions of Leptanilla species.

Figures

Figure 9. Leptanilla acherontia, holotype (CASENT 0842720), worker A profile view B dorsal view C full-face view. Scale bars: 0.5 mm.

Figure 10. Mandibles of Leptanilla acherontia (CASENT 0842721), dorsal view, worker. Bifid tooth marked with arrow. Scale bar: 0.05 mm.