Myopias darioi

This species is known from a single rainforest locality in Sabah. The type series was collected from a nest in a fallen log that contained a full range of castes.

Identification
Probst et al. (2015) - The worker of M. darioi is distinguished by the following characteristics: Head slightly longer than broad, subquadrate, sides subparallel and very weakly convex; posterior head margin concave. Eyes small, round, composed of a single lenticular ommatidium; diameter 0.03–0.05 mm. Mandibles linear, robust, somewhat short; basal angle poorly defined; prebasal tooth robust, height about half length of basal blade of masticatory margin. Antennal scapes not surpassing head posterior margin in repose. Clypeal lobe subrectangular, slightly wider than long; anterolateral corners edentate, rounded; sides posteriorly divergent, anterior margin feebly convex. Mesosoma robust, subrectangular in profile, with impressed metanotal groove; dorsopropodeum almost twice as long as mesonotum. Petiolar node longer than tall in profile, node dorsum convex. Abdominal segment III with distinct cinctus (constriction) between pre- and postsclerite. Sculpture predominantly smooth and shining, with spaced, indistinct piligerous punctures, especially on head; lateropropodeum obliquely costulate; dorsopropodeum face finely roughened in part. Color light ferruginous to dark ferruginous red. Myopias darioi workers are most similar to Myopias tenuis, but differ as follows: Mandibles shorter, more curved, with a basal tooth; frontal lobes larger and broader; anteromedian clypeal process shorter, broader, and broadest near its base. The gyne is similarly identifiable as the worker. At present, knowledge of male Myopias is too scant to develop a concise diagnosis for the male of M. darioi. However, male M. darioi may be distinguished by petiolar and subpetiolar process shape, size and shape of abdominal sternum III prora, strength of the cinctus, propodeal sculpture, and coloration as described below.

Myopias darioi runs to couplet five in the key of Xu et al. (2014), where it fails as the worker has a median clypeal lobe which is about as broad as long, basal mandibular tooth robust and acute, and petiolar node about as broad as long and lateral faces narrowing anteriorly in dorsal view. Regardless of how close the match between M. darioi and Myopias bidens or Myopias philippinensis may be in the key, M. darioi differs starkly in having the anterior margin of the median clypeal lobe linear (rather than bidentate), the eyes strongly reduced (rather than large and conspicuous), and the basal mandibular tooth situated basally on the masticatory margin, among several other characters. In the keys of Emery (1900) and Willey and Brown (1983) M. darioi keys to M. tenuis, but may be distinguished from all other described species, and M. tenuis in particular, by characters indicated above.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Malaysia.

Biology
Probst et al. (2015) - The colony containing the type series of M. darioi was nesting inside a fallen, dead trunk, circa 10 meters length, in an advanced stage of decomposition. The nest contained two dealate gynes, 35 workers of which four were undoubtedly callow, four males, and brood of all stages, with pupae predominating (48 pupae, of which two were male and two were gyne pupae). The trunk was completely damp. In some parts, there was water filling the cavities. The trunk was occupied by a high density of nesting ants, e.g., Myrmecina sp., Odontomachus rixosus, Pheidole spp., Ponera sp. dealate gyne, Pseudoneoponera sp., Tetramorium sp., representatives of various beetle families, and a Malaysian forest scorpion, Heterometrus spinifer (Ehrenberg, 1828). The Myopias colony was in the trunk portion next to the soil with harder bark than the surrounding structure. The nest was 15 cm long and approximately 9 cm in diameter, with 3 cavities. Workers and brood were scattered through two of the chambers. One large chamber was the “kitchen dump” replete with beetle remains of various families (Fig 6A), represented by head capsules, mandibles, elytra, and pronota (Fig 6C). Additional galleries leading away from the midden contained further beetle remains. Also found were ant remains, including two head capsules, three fourth abdominal segments (two of them attached with postpetiole) and two petioles of a Proceratium species; and one Gnamptogenys mesosoma with attached mesocoxae, metacoxae, and petiole. All nest remains are deposited in MZSP Collection (R. S. Probst #352). Finally, there were tiny cotton-like balls resembling fungus which workers were removing from the nest. It is unknown whether M. darioi build new nests or co-opt pre-existing cavities, although some observations were made of workers excavating a nest entrance.

Based on the consumed remains retrieved inside the nest and the galleries leading out of the nest, beetles and other potential prey were gathered by RSP inside the trunk one day after collection of the colony. In the Maliau Basin Studies Center laboratory mixed sets of arthropods were offered in a Petri Dish to the ants in three “cafeteria experiments”, in which the ants were allowed to choose prey from a variety available in the field: Adult ants (workers of Cerapachys and of a small Leptogenys species), isopods, millipedes (three species), geophilomorph centipedes, entomobryomorph collembolans, cricket (Gryllidae) nymphs, termite workers (Nasutitermes sp.), cucujoid and tenebrionid beetle larvae and adults. The ants readily accepted adult beetles from two tenebrionid species (a Platydema spp. [Diaperini] and a Micropeneta spp. [Gnathidiini]) (see video). Apparently, the clypeal lobe assists the attachment of the ant to the promesonotal articulation of the beetle’s pronotum, allowing the ant to hold the prey and sting it; the other organisms were consistently ignored. This stands in contrast to the other known prey preferences of Myopias. The origin of the ant remains inside the nest is unknown; these may have been scavenged, preyed upon, or existed in the nest prior to use by M. darioi.

Ponerine ants are known to prey on a substantial range of organisms (Pfeiffer et al. 2014), with the diversity of mandibular and dentitional morphology correlated to hunting strategies (Schmidt & Shattuck, 2014). The head capsules of Myopias species are similar in appearance to those of the African millipede-specialist genus Plectroctena, an observation reflected in the historical classification of the two genera (plus Myopias’ junior synonym Trapeziopelta) in the former subtribe “Plectroctenini” in Emery’s (1911) contribution to the Genera Insectorum series. These similarities include minute to absent eyes, enlarged frontal lobes, long curved mandibles, and presence of a midclypeal lobe (although absent in some Myopias species); these characters are associated with the capture of hard and round prey (Déjean et al., 2001). It has been hypothesized that the clubbed antennae of cryptobiotic ponerines could aid in prey detection and movement in low light conditions or in narrow cavities (Schmidt & Shattuck, 2014). Despite the similarity of the head capsule of Myopias with Plectroctena, it is apparent that Myopias has a relatively catholic diet.

Few ponerines are known to prey on adult beetles, making the observed preference of M. darioi for beetles much more notable. Prior records of preferential predation on beetles include tenebrionid specialists, the South African Streblognathus (Brown 2000), and a species of Platythyrea (Platythyrea arnoldi). Beetles offered to M. darioi workers in the present study were rapidly detected and were seized dorsally and stung ventrally. Prey were transported between the workers’ legs with the prey’s venter facing upward parallel to the ant’s body axis (Fig 6B), preventing the beetle from clinging to the ground. This manner of prey carriage resembles that observed in Dorylinae (Déjean et al., 1999; Gotwald 1995; Schatz et al., 2001). Given the disinclination of other ground-dwelling ants to hunt adult beetles in similar environments, the preference of M. darioi for beetles may represent a case of competitive release. Myopias, with its considerable diversity of mandibular form, may be a model group with which to study the ecology and evolution of prey choice in a comparative framework.

Nomenclature

 * . Myopias darioi Probst & Boudinot, in Probst, Guénard & Boudinot, 2015: 196, figs. 1-6 (w.q.m.l.) BORNEO (East Malaysia: Sabah).
 * Type-material: holotype worker, 31 paratype workers, 2 paratype queens, 3 paratype males.
 * Type-locality: holotype Malaysia: Sabah, Maliau Basin Studies Centre, Bird Race Trail, 4.7404041°N, 116.97702°E ±300 m., 225 m., 27.vii.2014, tropical rainforest, nest in dead trunk, #352 (R.S. Probst); paratypes with dame data.
 * Type-depositories: MZSP (holotype); AMNH, ANIC, BBPC, BMNH, CASC, DZUP, FMNH, MBSM, MCZC, MHNG, MZSP, NHMB, PSWC, RSPC, UCDC, UPLB, USNM (paratypes).
 * Status as species: Jaitrong, Wiwatwitaya & Yamane, 2020a: 618 (in key).
 * Distribution: Malaysia (Sabah).

Worker
Measurements, holotype: HL 1.0, TL 5.09, HW1 0.80, HLA 0.31, CLL 0.10, CLW 0.13, MDL 0.62, SL 0.67, PDL 0.15, AFL 0.41, EL 0.05, EW 0.03, PRL 0.69, ML 1.38, MH 0.63, SDL 0.22, MFL 0.72, MTL 0.70, MBL 0.57, PTH 0.45, PTL 0.50, GL 1.6. Indices: CI 80.0, CS 0.90, CLI 75, MCI 61.7, SI 83.3, ESI 7.50, EI1 0.09, EHI 16.2, MI 45.5, MFI 1.12, PTI 111. Measurements, paratypes (n=6 of 31, range downward from size of smallest to biggest individual): HL 0.83–1.0, TL 4.31–5.43, HW1 0.72–0.83, HLA 0.29–0.32, CLL 0.07–0.11, CLW 0.12–0.14, MDL 0.55– 0.65, SL 0.56–0.72, PDL 0.13–0.18, AFL 0.33–0.40, EL 0.03–0.05, EW 0.03, PRL 0.53–0.73, ML 1.16–1.44, MH 0.50–0.64, SDL 0.17–0.22, MFL 0.59–0.75, MTL 0.58–0.71, MBL 0.48–0.57, PTH 0.38–0.45, PTL 0.42–0.50, GL 1.3-1.9. Indices: CI 79.0–85.2, CS 0.78–0.92, CLI 57.1–78.6, MCI 59.7–65.8, SI 77.9–87.8, ESI 5.97–7.59, EI1 0.07–0.10, EHI 11.1–17.1, MI 42.1–45.2, MFI 1.08–1.21, PTI 106.3–120.8.

Head

Head distinctly longer than broad, subrectangular; eyes situated anteriorly the middle length of head; in full-face view sides very weakly convex, widest posterad eyes and narrowing almost imperceptibly to posterolateral corners; posterior border medially concave, concavity nearly angular. Palpal formula 2,3; basal segment of maxillary palp short and broad, apical segment very long (at least five times longer than basal segment), slender and with an apical sensillum about ½ of its length. Labial palpi each with 3 segments; basal segment about twice as long than second segment, with 2 adjacent proximal sensilla; second segment with one submedian lateral sensillum; third segment “bottleneck”-like, slightly longer than the basal segment, with 3 apical sensilla. Labrum bilobed apically, each labral lobe bearing apically a slightly upturned tooth (in some specimens, almost impossible to see without dissection).

Mandibles robustly linear and subfalcate, comparatively short, down-curved in profile view, with four teeth; basal angle poorly defined but distinct; basal blade of masticatory margin from basal angle to base of prebasal tooth less than half length of inner mandibular margin; prebasal tooth robust, height slightly shorter than half basal blade length from basal angle; diastemma between prebasal tooth and next tooth slightly shorter than inner mandibular margin; apical tooth sharp, subtended by minute and sharp subapical tooth; distinct, isolated, submedian tooth present situated basad (approximately 0.12 mm) from subapical tooth, both subapical and prebasal teeth blackened and narrowly rounded apically. Mandibular oblique basal groove present, lateral continuation very distinct. Median clypeal lobe subquadrate, slightly wider than long (CLL 0.10 mm, CLW 0.13 mm), with sides weakly concave and slightly divergent anteriorly, widest at base; anterior margin roughly linear; lateral and anterior margins meeting at nearly 90°. Compound eye reduced, lenticular, consisting of a 4–5 unpigmented ommatidia (pigmentation and size variable in paratypes), with strong furrow extending dorsad orbital groove forward onto lateral clypeal portion. Frontal lobes long and very broad, slightly translucent. Median longitudinal frontal sulcus deep, widest posterad frontal lobes, extending slightly beyond midlength of head as measured from clypeal process. Antennal scapes somewhat robust in comparison with other Myopias species, moderately bowed, slightly incrassate; not exceeding posterior head margin in full-face view. Pedicel longer than wide; funicular segments I to VI wider than long, followed by an indistinctly 4-merous club; club longer than wide, apical antennomere slightly longer than antennomeres IX and X combined.

Mesosoma

Mesosoma robust; mesosomal dorsum nearly linear in profile view, mesonotum raised anteriorly above pronotum and propodeum, sloping caudad, about ⅓ length of dorsopropodeum; meso-metanotal groove distinct, narrow. Mesonotum about ⅔ length of pronotum in dorsal view. Propodeum subrectangular in profile view, dorsopropodeum nearly linear in profile view, weakly convex, round into posteropropodeum at somewhat more than 90°; propodeum with feeble median impression where dorso- and posteropropodeum meet; declivity more or less flat, with lateral boundaries distinct, submarginate. Pronotal anterior and dorsal faces meeting at slightly more than 90° in profile view, this anterodorsal margin subangular; dorsal face slightly more convex than dorsopropodeum. Propleurae anteroposteriorly wide in profile view; meso- and metatibiae each with one simple and one pectinate spur, protibial calcars large; ventrolateral apical protibial margin with row of stout lamellar setae. Meso- and metasternal process present; mesosternal process well developed (about ⅙ length of mesocoxae), its apex acute and slightly curved. Mesosternal process narrower, its apex more rounded. Metasoma Petiolar node subcuboidal, slightly taller than wide in profile view; dorsal face weakly convex, highest posterad midlength; anterior face straight to feebly concave in profile view, sloping posterodorsally; posterior face convex in side view sloping anterodorsad. In dorsal view, anterolateral corners of node very prominent; node widest behind, with sides convex, slightly wider than long. Subpetiolar process large, vaguely wedge-shaped; anterior margin short, oriented dorsoventrally; anteroventral margin longer, oblique, obtusely rounding into longer, sinuate posteroventral margin.

Abdominal tergum III almost as broad as long in dorsal view, anterodorsal border slightly concave medially. Abdominal sternum III prora robust, triangular, margined by strong, transverse, anterior carina. Abdominal tergum IV slightly wider and longer than tergum III in dorsal view; cinctus distinct, wide, and cross-ribbed. Sting long, sharp, upcurved (extended up to 0.59 mm in the holotype and some paratypes). Sculpture Mostly smooth and shining, with regular, inconspicuous, dilute piligerous punctures; on head dorsum laterad midline, piligerous punctures numerous, small, averaging about 0.01 mm in diameter or smaller, mostly in space between eye and median sulcus; small piligerous punctures distributed very sparsely on mandibles, postgenal bridge, genae, pronotum, mesonotum, and metasomal terga. Moderately coarse piligerous punctures present on petiolar node and remaining abdominal terga. Antennae and legs mainly smooth and shining, very finely punctate, punctation density increasing apically. Lateropropodeum with fine, oblique costulation, rising caudad. Propodeal declivity anterodorsally feebly, finely, transversely strigulose, smooth and shining below. Anteroposterior carinulae present on petiolar tergum. Setation Consisting of somewhat fine, filiform, erect to suberect setae of uneven length (from 0.03 to 0.15 mm long), distributed over dorsal surfaces of body, venter of head, metasoma, fore coxae, and most surfaces of appendages; more abundant on the apex of gaster dorsa. Mandibles bearing short to elongate (at its apex) filiform setae. Anterior portion of petiolar peduncle bearing erect and short hard setae, anterior portion of subpetiolar process bearing filiform, suberect and posteriorly curved hairs. Decumbent pubescence is present on anteromedian pronotal lobe, directed mesad; denser on anterior surfaces of mid coxae, and on all tibiae and tarsi. Coloration Color ferruginous red; appendages and metasomal apex slightly lighter. Variation Noticeable size variations between workers in mesosoma width, scape, gaster, hindtibia, and total length. Distinctness and density of punctures varies from fine and sparse in small specimens to coarse and denser in large specimens, mostly on head dorsum, in space between eyes and median sulcus; little variation present on mesosoma, and metasomal tergites. In some specimens subpetiolar process may be more produced or less produced at mid-length, and posteroventral margin angled instead of sinuate. Coloration varies from light to medium ferruginous red to dark brownish red; some workers, possibly callow, light orange brown.

Queen
(n=1): HL 1.08, TL 6.07, HW1 0.90, HLA 0.23, CLL 0.12, CLW 0.17, MDL 0.67, SL 0.78, PDL 0.19, AFL 0.41, EL 0.32, EW 0.27, LOD 0.08, MOD 0.08, OOD 0.45, PrL 0.67, ML 1.66, MH 0.91, MTL 0.63 MTW 0.72, MLL 0.28, MLW 0.33, SDL 0.24, MFL 0.83, MTL 0.77, MBL 0.63, PTH 0.52, PTL 0.53, GL 2.1. Indices: CI 83.7, CS 0.99, CLI 70, MI 88.9, SI 86.1, ESI 40.9, EI1 0.59, EI2 90.0, EHI 136, TPR 0.41, MI 54.7, MTI 115, MLI 118, MFI 1.09, PTI 103. Specimen description of dealate gyne, differing from associated worker by following: Body slightly longer, darker in color, prevailingly piceous. Promesonotal articulation deeply impressed, mesoscutum trapezoidal with slightly protruding borders, anterior edge convex in dorsal view; in profile view, its anterior portion slightly bulged and smoothly curved caudad. Parapsidal lines directed anteriorly from transscutal suture to mesoscutal disc, running along the parascutal carina; slightly divergent anteriorly. Tegulae well developed. Scutoscutellar sulcus present. Scutellum hexagonal, sides depressed, costulae surround depressions alongside wing bases. Metanotum present, anterior face straight, posterior face slightly convex. Oblique mesopleural furrow linear, directed posterodorsally. Upper metapleuron [metanepisternum] oblong. Metanotal-propodeal sulcus deeply impressed. Posterior face of propodeum flat. Propodeal spiracle rounded, accommodated into lateropropodeal excavation. Anterior face of petiole more oblique than in workers, narrowing upward. Gaster relatively larger than in the worker. Sculpture Punctae coarser on head, in space between eye, and around median sulcus. Posterior region of lateropronotum with small costulae, punctures present on anteromarginal area of mesoscutum and anterodorsal margin of dorsopropodeum. Longitudinal striations present in part of propodeal declivity. Sculpture on lateropropodeum similar to workers, but deeper, costulation present on lateroposterior region of petiole in profile view. Setation Pubescence between the frontal lobes and anterior portion of eyes more marked than in workers. Suberect pilosity slightly more abundant on pronotal dorsum. Sterna of gaster bearing more abundant pilosity than the conspecific workers. Coloration Frons, except area adjacent to frontal surface, temple, and clypeal margin infuscated, resembling an inverted Y. On mesosoma, centers of mesoscutum and scutellum are blackish; marginal areas of these and other sclerites lighter, more reddish; abdominal tergites III and IV similarly colored. Appendages lighter, brownish red.

Male
(n=2): HL 0.55–0.56, TL 3.55–3.83, HW1 0.53, HW2 0.63–0.65, HLA 0.11, MdL 0.13–0.15, SL 0.13, PDL 0.1, A3L 0.21–0.22, AFL 0.30–0.32, EL 0.28, EW 0.20–0.21, LOD 0.07–0.08, MOD 0.07, OOD 0.18, PRL 0.20–0.21, ML 1.20–1.22, MH 0.75–0.78, MTL 0.53–0.57, MTW 0.55–0.58, MLL 0.15, MLW 0.27–0.28, SDL 0.18–0.19, HFL 0.69, HTL 0.64–0.65, MbL 0.53–0.56, PTL 0.33–0.35, PTH 0.30, GL 1.3-1.6. Indices: CI 92.7–97.0, CS 0.54–0.55, MCI 24.2–26.5, SI 23.4–25.4, ESI 213–227, SAI 60.0–61.5, EI1 0.89–0.92, EI2 82.1–82.9, EHI 262–283, TPR 0.37–0.38, MI 61.5–64.9, MTI 103–105, MLI 124–127, MFI 0.76–0.78, PTI 111–117.

Head

Head longer than broad, excluding eyes. Palpal formula 5,3, with third maxillary palpal segment shorter than the fourth, and second labial palpomere broader and shorter than the first. Labrum trapezoidal, length from base to apex slightly less than maximum width of mandibles. Mandibles subspatulate, medial and lateral margins subparallel and terminating in a triangular apex. Clypeus in profile view weakly convex, not bulging. Antennal toruli separated from anterior tentorial pits by more than two maximum antennal socket diameters. Compound eyes somewhat large, taking up about one-third head length in profile view. Medial compound eye margin linear, posterior eye margin weakly emarginate. Mesosoma Anterior pronotal margin well-developed bulging, oriented dorsoventrally (perpendicular to cephalocaudal axis). Propleuron without distinct ventrolateral process. Mesoscutum about as broad as long. Notauli V-shaped and not meeting medially. Parapsidal lines clearly impressed, directed anterolaterally, slightly parallel to parascutal flange and extended to posterior limit of notaulus. Mesepimeron strongly produced posterodorsally dorsad spiracular sclerite. Oblique mesopleural furrow linear, directed posterodorsally, with small posteriormost section bent and directed posteriorly. Metascutellum ecarinate medially and not produced posteriorly. Disc of dorsal metapleuron lenticular in shape. Anterodorsal metapleural margin not emarginated to receive spiracular sclerite. Dorsolateral metacoxal margin subangular. Propodeum posteriorly elongate, dorsopropodeum and posteropropodeum differentiated by carina in profile view and about equal in length. Two tibial spurs on each middle and hind leg (one simple, one pectinate), fore legs with one pectinate spur. Distal margin of each metatibia bearing a row of hard lamellar setae at its lateroventral portion. Probasitarsal notch comb present, extending from the apex to middle portion of probasitarsomere. Metasoma Petiole nodiform; apex situated posterad petiole midlength. Petiolar tergum anterodorsal face weakly concave, node strongly and anteroposteriorly narrowly convex, node dorsum not overhanging linear posterior face. Petiolar tergum anterolateral corners carinate but not strongly produced, not translucent; in dorsal view anterolateral processes simple, rounded, not angular or flanged. Petiolar sternum in profile anteroventrally lobate, lobe truncate and margined anteriorly and laterally by carinae; carinae diverging toward midlength then converging posteriorly; posterior two thirds of sternum tapering and sinuate in profile view. Abdominal tergum III slightly swept back. Abdominal sternum III prora strong, bulging, triangular in profile view, anteriorly carinate, and with four subparallel short strong carinae extending posteriorly from anterior margin, and lacking median carina. Abdominal sternum IV with weak median depression bordered by weak swelling which form low welts near posterior margin. Cinctus between abdominal pre- and postsclerites IV strong, deep, crossribbed, and very broad.

Forewing Rsf1 and Mf1 nearly parallel, Mf1 distinctly curved. Mf2 absent, Rs+M with second abscissa distad 1m-cu. 2rs-m juncture with Rsf distad 1r-rs. Mf1 diverging from M+Cu distad cu-a. Submarginal cell 2 slightly shorter than marginal cell 1. Hindwing R+Rs extending tubularly well beyond 1rs-m.

Sculpture Piligerous punctae weakly impressed. Clypeus smooth, without raised sculpture. Posterior mesoscutal margin without striations. Dorsopropodeum without longitudinal carinae, although anteroposteriorly short paired carinae occur near the anterior propodeal margin and along the posterior margin of the dorsopropodeum. Lateropropodeum with four transverse parallel carinae. Posteropropodeum completely set off by strong carina. Propodeum otherwise mostly smooth and shining. Petiolar tergum predominantly smooth and shining, with lateral longitudinal carinulae. Genitalia See figures 4C–I. Setation Mandibular dorsum bearing four long and filiform setae, clypeus, frons, and vertex with dense, shaggy-appearing setae. Funicular antennomeres with long subdecumbent setae in addition to short appressed setae. Compound eyes bearing interommatidial setae. All femora and tibiae with distinctly elongated erect setae sparsely distributed among denser shorter erect to subdecumbent setae. Propodeum dorsolaterally with dense patch of setae. Gaster with sparsely erect to suberect filiform setae. Coloration Exceptional. Head bright orange, more yellow around mouthparts; mandibles and palps light yellow; ocellar area infuscated. Scape honey yellow, pedicel light yellow, antennomere 3 light yellow to brownish honey yellow apically, antennomere 4 all dark, becoming progressively darker until black; apex of antennomere 13 golden yellow. Pronotum and propleurae honey yellow. Mesoscutum bright orange, more yellow anteriorly; axillae honey yellow, mesoscutellum black. Mesopectus predominantly black, fading to brownish-golden toward margins. Metascutellum black, lateral metascutellar areas lighter. Lower metapleuron black, becoming brownish-golden near metapleural gland area; upper metapleuron nearly black, becoming lighter near margins; spiracular sclerite golden yellow. Propodeum almost entirely black, lighter near dorso-posteropropodeal margin and petiolar foramen. Petiole almost entirely black, becoming lighter near posterior collar; laterotergum brownish-golden. Abdominal terga III-VIII and sterna III-IX mostly dark brown, becoming brownish-golden along lateral and posterior margins; segments becoming slightly lighter near posterior terminus. Coxae and trochanters white; femora light yellow basally to golden yellow apically; tibiae golden yellow; protarsomeres light yellow, meso- and metatarsomeres white with yellowed apical margins. Wing veins lightly pigmented, mostly clear, white, or yellowish.

Larva
Final-instar larva: length (through spiracles) about 2.6 mm. Body shape platythyreoid, thoracic segments forming long and slender neck, entire integument spinulose. Cranium anteriorly elongate, anteroposterior length slightly less than twice dorsoventral height in profile view, and a third longer than broad in dorsal view, subelliptical. Antennae highly posteriorly positioned. Labrum subtrapezoidal, length subequal to width, and posterior surface spinulose. Mandibles dinoponeroid, apices directed slightly ventrally, curved and nearly completely exposed, moderately sclerotized, long and with two short subapical teeth on the inner border. Abdomen subovoid, anus ventrally positioned. Ventral surfaces of thoracic segments with numerous rows of posteriorly projecting spinules. Tubercles on body moderately numerous (80–90), subconical, with an integumentary spinule on the apex and often with simple setae near its base; each thoracic segment with one lateral subconical tubercle while each abdominal segment except AX with two. Pre-pupa: similar in size compared to full grown larva, same body shape and integumental protuberances. Numerous rows of posteriorly projecting spinules on the ventromedial surface of thoracic segments.

Type Material
Holotype worker: MALAYSIA, SABAH: Maliau Basin Studies Centre, Bird Race Trail, 4.7404041°N 116.97702°E, ± 300 m (GPS deviation), 225 m.a.s.l., 27 July 2014, tropical rainforest, ex. nest in dead trunk (R. S. Probst #352) []. Paratype workers: Same data as holotype [, one worker;, one worker; BEBC, one worker; , one worker; , two workers; , one worker; , one worker; , 4 workers; , two workers; , one worker; MNH, three workers, , 8 workers; , one worker; , one worker; RSPC, one worker, , one worker; USNM, one worker]. Paratype gynes: Same data as holotype [MZSP, one gyne; MNH, one gyne]. Paratype males: Same data as holotype [BEBC, one male, MZSP, two males].

Etymology
The epithet of this species honors Dario D’Eustacchio, a myrmecologist and one of the participants in the 2014 Ant Course. He was a Ph.D. student at the University of Rome. He died tragically in a car accident shortly after; the authors mourn his loss.