Body size medium, 4 mm in length. Pronotum with median furrow. Elytral declivity in females with sutural tubercle; margin of ventrite 4 produced into a lamina, with bifurcate median process (Fig. 100); margin of ventrite 5 with a slim horn on either side of genital opening (Fig. 100).

Body length 3.60 mm to 4.55 mm (X‒ = 4.19 mm, s = 0.36, n = 8). Integument black. Dorsum densely covered with moderate yellowish brown to greyish brown appressed scales, pale “V” on elytral declivity often present; pronotum same colour as elytra, with pale posterolateral maculae lining up with pale maculae on humeral angles of elytra, especially prominent in females. Femora and tibiae with dense appressed scales concolorous with elytral scales, usually with pale band in distal 1/4 of femora. Tarsi with integument deep orange. Rostrum. Length 0.72 mm to 0.96 mm (X‒ = 0.85 mm, s = 0.09, n = 7), width 0.52 mm to 0.65 mm (X‒ = 0.59 mm, s = 0.05, n = 7), length/width ratio 1.33 to 1.55 (X‒ = 1.44, s = 0.07, n = 7). Epifrons with appressed scales imbricate; setae dolabriform, decumbent, dark; median and lateral carinae not evident. Dorsal carinae arched over antennal insertions. Lateral area ventral of antennal insertions with thick setae, without appressed scales. Antennae. Scapes in repose reaching hind margin of eye; covered with appressed scales and setae. Funicular segments moderately articulated; segments 1 clavate, subequal in length to 2; segments 2 clavate, about two times longer than 3; segments 3 to 4 clavate; segments 5 to 7 oblately spheroid. Pronotum. Length 1.07 mm to 1.29 mm (X‒ = 1.16 mm, s = 0.09, n = 7), width 1.58 mm to 2.08 mm (X‒ = 1.88 mm, s = 0.20, n = 7), length/width ratio 0.77 to 0.97 (X‒ = 0.87, s = 0.07, n = 7); in dorsal view widest in anterior 1/4, lateral margins evenly curved. Anterior margin slightly emarginate medially, posterior margin straight. Disc in dorsal view evenly convex, with median furrow; appressed scales imbricate; setae dolabriform to claviform, decumbent, dark to concolorous. Postocular lobes moderately developed. Elytra. Length 2.40 mm to 3.09 mm (X‒ = 2.78 mm, s = 0.26, n = 7), width 1.58 mm to 2.08 mm (X‒ = 1.88 mm, s = 0.20, n = 7), length/width ratio 1.39 to 1.61 (X‒ = 1.48, s = 0.08, n = 7). Anterior margin curved posteriad in middle, humeral angles rounded. Appressed scales imbricate. Setae claviform, decumbent, concolorous. Striae moderately impressed; interstriae slightly convex. Interstriae 1 at declivity flat in males, produced into a tubercle in females. Interstriae 3 and 5 at declivity swollen in both sexes. Apex in lateral view square in males; produced ventrad in females. Thoracic ventrites. Mesoventral process rounded. Mesanepisterna, mespimera, metanepisterna and metaventrite densely clothed with pappolepidia. Abdomen. Ventrites sparsely clothed, appressed scales most numerous medially, pappolepidia becoming dominant laterally. Apex rounded. Males with ventrite 1 strongly depressed medially; ventrite 5 flat. Females with ventrite 1 flat; ventrite 4 with posterior margin produced medially into a bifurcated lamina (Figs 100, 101); ventrite 5 with median furrow, posterior margin broadly emarginate with a strong horn on either side of emargination. Male genitalia. Figs 39, 40. Penis with apex acute, upturned; ostial region thickened, forming a crest. Endophallus with lightly sclerotised plate proximally from primary gonopore, gonoporial sclerite large, with distinct posterior lobes. Temones 0.72 times as long as pedon. Female genitalia. Figs 41–45. Distal gonocoxites slender, 2.7 times longer than high. Bursa copulatrix long; not constricted anteriorly of proximal gonocoxite; sclerite horseshoe-shaped, squat. Sternite 8 narrowly rounded apically, membranous laterally. Everted ovipositor 3.44 mm in length, 0.75 times body length.

KX191432. 28S. KX192009. ArgK. KX191719. CAD. KX191161.

Holotype. Female (NZAC). Specimen mounted on card teardrop; abdomen removed, dissected and mounted in DMHF on white card below specimen; otherwise entire; elytra parted at apex. Labelled ‘NEW ZEALAND CO / Gem Lake / Umbrella Mountains / 10 Feb 2014 / SDJ Brown’ [printed, cream card], ‘On Phyllachne cushion / 1430 m / 45.5703°S, 169.1021°E [printed, cream card], ‘Irenimus taxonomy / and systematics / SDJ Brown / PhD Thesis 2012–2015 / IRE4875’ [printed, cream card], ‘HOLOTYPE / Austromonticola / atriarius / Brown 2017’ [printed, red card]. Genomic DNA extract from enzyme digestion of abdomen: E300 (NZAC). CAD sequence KX191167; COI sequence KX191438; ArgK sequence KX191722; 28S sequence KX192015.

Paratypes. A total of 7 specimens (4 males, 3 females) designated as paratypes, bearing blue paratype label. Paratype specimens deposited in NHM, IACC, LUNZ, NZAC.

CO. Gem Lake [45°34.236'S, 169°6.384'E, A], 14–15 Dec 1985, Barratt BIP, 1300 m (NHM: 1); Gem Lake [45°34.236'S, 169°6.384'E, A], 14–15 Dec 1985, Barratt BIP, 1400 m (IACC: 1); Gem Lake [45°34.236'S, 169°6.384'E, A], 15 Dec–15 Jan 1986, Barratt BIP, 1430 m (NHM: 1, IACC: 1, LUNZ: 2, NZAC: 1).

Fig. 116. South Island: CO: Umbrella Mountains.

Label data: 1300 m to 1430 m (X‒ = 1410 m, s = 46, n = 8). Georeferenced data: 1297 m to 1423 m (X‒ = 1313 m, s = 44, n = 8).

From the Latin noun atriarius, ‘porter, doorkeeper’, in reference to the armature surrounding the female genital opening and alluding to a possible function of preventing unwanted mating attempts. The name is a noun in apposition.

Found in cushionfield, with a single specimen recorded in association with Phyllachne.