Holotype. Australia • 1 worker; Western Australia, Newman; 22°44'S, 119°02'E; ca 575 m a.s.l.; 8 Mar. 2023; Jane M. McRae leg.; collected via subterranean scraping; BENNSPECIMENID_746962.1; WAM.

Paratype. Australia • 1 worker; same data as for holotype; BENNSPECIMENID _746962; WAM.

Unfortunately, both the holotype and paratype specimens were brittle and partially damaged during the mounting process. A photograph of the fully intact specimens in liquid prior to mounting is shown in Fig. 1. During mounting of the holotype, the postpetiole was disconnected from the petiole and gaster. The paratype was similarly disconnected at the petiole and gaster. Broken segments of each specimen were glued onto its respective mount. The full-body images of the mounted holotype in profile view (Fig. 2) and dorsal view (Fig. 3) are composites in which the postpetiole and gaster were imaged separately in the respective views, and subsequently reattached to the body digitally, while ensuring consistency of scale.

All measurements are in millimetres (mm).

Holotype: HW 0.26; HL 0.35; SL 0.36; MaL 0.21; WL 0.59; PrW 0.16; MW 0.12; PTL 0.28; PTH 0.08; PTW 0.07; PPL 0.24; PPW 0.10; PPH 0.10; CI 73, SI 139, MI 81, PI 25, PPI 39, PPHI 42.

Paratype (n = 1): HW 0.27; HL 0.36; SL 0.35; MaL 0.20; WL 0.61; PrW 0.16; MW 0.12; CI 75, SI 128, MI 75.

Head. Head longer than wide (CI = 73–75). In full-face view (Fig. 4), posterior margin of head slightly concave. Lateral margins of head slightly convex. Eyes absent. Anterior clypeal margin extending forward with two rounded lobes anterolaterally and slightly concave on its anteromedian portion. Median portion of clypeus raised; frontoclypeal process present and concealing labrum. Mandibles long relative to head (MI = 75–81) and armed with three teeth. Apical tooth acute and larger than subapical and basal teeth. Basal tooth larger than subapical tooth with tip approximately perpendicular to mandibular margin; margin distal to subapical tooth irregularly serrate. Antennal insertion exposed. Antennae with 12 segments. Scape elongated, extending well beyond mid-point of head (SI = 128–139); margins subparallel, expanding slightly before tapering at apex. Pedicel longer than broad and constricted at separation from scape; constriction separating pedicel from flagellum not pronounced. Flagellum filiform; all flagellomeres longer than broad. Antennomere 12 approximately double the length of previous flagellomeres with apex tapered.

Mesosoma. In dorsal view, maximum width of pronotum (PrW = 0.16 mm) wider than posterior portions of mesosoma (Fig. 3). In lateral view, pronotal dorsum slightly convex, tapering along anterior margin, with posterior margin slightly elevated above mesonotal dorsum (Fig. 2). Promesonotal suture clearly visible in both lateral and dorsal view. In dorsal view, mesonotum constricted anteriorly, with lateral margins gently convex and approximating maximum width at fusion with propodeum. In dorsal view, propodeum not constricted anteriorly, with outline of posterior margin trapezoidal (Fig. 3). In lateral view, propodeal dorsum raised and strongly convex, with posterior forming a strongly convex propodeal declivity at an approximate 65° angle (Fig. 2). Metapleural gland bulla and propodeal spiracle visible. Coxae robust, pro- and mesocoxae well separated; distal leg articles elongated.

Metasoma. Metasoma elongated in both dorsal and lateral view (PL + PPL ≈ WL). In dorsal view (Fig. 3), petiole four times as long as wide (PI = 25), with lateral margins subparallel at anterior and convex after mid-point to achieve maximum width; posterior margin convex and rounded. Postpetiole longer than wide (PPI = 39), with similar shape to petiole but wider and more rounded posteriorly. In lateral view (Fig. 2), petiole with dorsal and ventral margins subparallel at anterior and convex after mid-point to achieve maximum height; posterior margin slightly concave. Subpetiolar process absent. Postpetiole with dorsal and ventral margins subparallel at anterior and diverging near mid-point, after which dorsal margin is weakly convex and ventral margin is strongly concave; posterior margin concave.

Sculpture. Sculpture absent. Most of the body slick and shiny (i.e. not a result of glare from diffusing light when imaging).

Pubescence. Pubescence present on most of the body, especially antennae and legs, but sparse to absent on propodeum and metasoma. Numerous suberect to erect setae on dorsal and ventral surfaces of pronotum, cranium, and mandibles. Long basal and subapical setae on mandibles.

Colouration. Pale gold to amber. Colouration slightly lighter at extremities.

Castes. Male and gyne unknown.

The species epithet pays tribute to the antagonist in the Harry Potter book series, Lord Voldemort, a terrifying wizard who, like the new ant, is slender, pale, and thrives in darkness. The species epithet is a noun, and thus invariant.

Only known from the type locality within the Pilbara region of Western Australia.

Leptanilla voldemort sp. nov. was collected from a hot grassland in the north-west Pilbara, a region characterised by very hot summers (average maximum 36–39 °C), low winter minima (average minimum 6–12 °C), low average annual rainfall (200–350 mm), and high evaporation (average annual potential evaporation 3200–4000 mm) (Eberhard et al. 2005). Both type specimens were collected from a 25 m deep mining exploration drill hole using a subterranean scraping method, whereby a weighted net was lowered to the base of the hole and dragged four times back to the surface against the wall of the hole (Halse and Pearson 2014). The drill hole was in a dry drainage line, with the subterranean substrate consisting of coarse alluvium near surface over banded iron formation at depth. Other organisms recorded from the drill hole include troglofaunal beetles of an unknown genus, troglofaunal flies of the genus Allopnyxia Freeman, 1952 and troglofaunal centipedes assigned to the genus Cryptops Leach, 1814. We are presently unable to ascertain whether colonies of L. voldemort sp. nov. inhabit topsoil, the subsurface alluvium, or voids in the deeper weathered banded iron formation. The colony size and structure of L. voldemort sp. nov. is unknown.

The worker of L. voldemort sp. nov. is easily distinguished from the other native Australian leptanilline species, L. swani Wheeler, 1932, which is evidently sympatric with L. voldemort sp. nov. (see new collection data below). First, L. voldemort sp. nov. has distinctly elongated mandibles (MI = 75–81) and antennae (SI = 128–139), while in L. swani these appendages are stouter and shorter (MI = 44–56, SI = 59–74). Second, L. voldemort sp. nov. possesses metasomal segments that are two to four times longer than wide (PI = 25, PPI = 39), while in L. swani these segments are almost as long as wide (PI = 56–70, PPI = 83–100). Finally, L. voldemort sp. nov. (WL = 0.59–0.61 mm) is larger in size than L. swani (WL = 0.35–0.45 mm). In general, the gracile phenotype of L. voldemort sp. nov. is distinctive among the genus Leptanilla, except for Leptanilla laventa Griebenow, Moradmand & Isaia, 2022, a species described from Iran. Specifically, the elongated antennae and petiole of workers in both L. voldemort sp. nov. (SI = 128–139, PI = 25) and L. laventa (SI = 160–163, PI = 29–32) are not observed in other Leptanilla species (SI<100, PI>31) (Griebenow et al. 2022; Griebenow 2024; Qian et al. 2024). Nonetheless, workers of L. voldemort sp. nov. can be distinguished from those of L. laventa based on several key morphological differences. First, in dorsal view, the shape of the petiole and postpetiole of L. voldemort sp. nov. is distinctly more elongated (PI = 25; PPI = 39) than in L. laventa (PI = 29–32; PPI = 59–64.7). Second, in lateral view, the propodeal declivity of L. voldemort sp. nov. is strongly convex and distinctly angular, whereas that of L. laventa is weakly convex and gently rounded. Third, in full-face view, the axis of the basal mandibular tooth of L. voldemort sp. nov. extends almost perpendicular to the mandibular margin, with the tip of the tooth forming an 80–90° angle with the medial mandibular margin, whereas in L. laventa, the basal tooth is recurved, with the tip of the tooth forming a 60–70° angle with the medial mandibular margin. Finally, L. voldemort sp. nov. (WL = 0.59–0.61 mm) is smaller in size than L. laventa (WL = 0.74–0.85 mm).

Below we provide measurements for three worker specimens of L. swani. Collection data for the first two specimens are as follows: Australia; 2 workers; Western Australia, Newman; 22°47'S, 119°9'E; ca 537 m a.s.l.; 9 May 2022; Jane M. McRae leg.; collected via subterranean scraping; BENNSPECIMENID_735794 and BENNSPECIMENID_735840; WAM. Collection data for the third specimen, a paratype of the species, is as follows: Paratype: Australia; 1 worker; Western Australia, Chittering; 31°27'S, 116°5'E; ca. 225 m a.s.l.; D. Swan leg.; CASENT0172006; ANIC.

BENNSPECIMENID_735794 (Fig. 5): HW 0.23; HL 0.31; SL 0.17; MaL 0.13; WL 0.44; PrW 0.15; MW 0.14; PTL 0.15; PTH 0.11; PTW 0.08; PPL 0.11; PPW 0.09; PPH 0.13; CI 72, SI 74, MI 56, PI 56, PPI 83, PPHI 117.

BENNSPECIMENID_735840: HW 0.22; HL 0.31; SL 0.16; MaL 0.12; WL 0.45; PrW 0.15; MW 0.12; PTL 0.15; PTH 0.11; PTW 0.09; PPL 0.12; PPW 0.10; PPH 0.12; CI 71, SI 72, MI 55, PI 59, PPI 87, PPHI 106.

CASENT0172006: HW 0.20; HL 0.28; SL 0.12; MaL 0.09; WL 0.35; PrW 0.13; MW 0.11; PTL 0.11; PTH 0.10; PTW 0.08; PPL 0.08; PPW 0.08; PPH 0.10; CI 69, SI 59, MI 44, PI 70, PPI 100, PPHI 125.