Myopias concava

Known to prey on millipedes. Colonies can contain up to 50 to 60 individuals and may have a single or multiple queens. The four nests that made up the type series were all found in rotten logs in rainforest habitat.

Identification
Willey and Brown (1983) - Worker and queen: A medium-sized, stout-bodied species with head slightly broader than long, widest just behind eyes. Median labral tooth absent, but an erect apical tooth on each labral lobe. Eyes of worker large and multifacetted, occupying more than a quarter of the length of the sides of the head. Posterior margin of head weakly concave; sides convex. Median lobe of clypeus distinct but very short, rectangular. Mandibles short and stout, each with 2 small teeth at apex, 2 large blunt teeth basad of these, and an obtusely rounded basal angle. Antennal scapes overreaching posterior margin of head. Trunk compact, promesonotum and propodeum subequal in length, forming separate weak convexities meeting at a distinct and depressed metanotal groove. Petiolar node massive, subcuboidal, broader than long. Anterior face of gastric segment I weakly concave as seen from dorsal view. Integument prevailingly smooth and shining, but with abundant, coarse piligerous foveolae, sometimes contiguous on head, and tending to become elongate on first two gastric terga. Color brownish red.

This very distinct species shows some affinities with the tenuis group in the presence of upturned teeth on the labral lobes and lack of median labral tooth, but it is different in its robust build, very prominent foveolate sculpture, shorter mandibles, and the concave anterior face of the first gastric tergum.

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

Castes
Both winged and ergatoid queens exist in this species (Willey & Brown 1983)

Nomenclature

 *  concava. Myopias concava Willey & Brown, 1983: 258, figs. 4, 18 (w.q.) NEW GUINEA.

Worker
Holotype: TL 7.1, HL 1.25, HW 1.31 (CI 105), ML 0.71 (MI57), MLO 1.26, SL l.ll (SI85), EL 0.33, WL 2.16, hind femur L 1.25, hind tibia L 1.20 mm.

Paratypes (n = 6 of 42 from 4 colonies, including largest and smallest specimens): TL 6.5-8.6, HL 1.17-1.43, HW 1.21-1.47 (CI 100-105), ML 0.67-0.81 (MI 53-66), SL 1.00-1.24 (SI 83-88), EL 0.30-0.40, WL 2.00-2.46 mm.

Head broader than long, with sides convex, broadest immediately behind eyes, and narrowed slightly in front of eyes; posterior border broadly and shallowly concave. (The head can be lengthened slightly by tilting it forward from the full-face plane; this has the effect of foreshortening the mandibles and deepening the concavity of the posterior margin, and of course decreasing CI.) Eyes large and convex, with about 18-19 ommatidia in the longest diagonal row, each eye occupying nearly 3/10 of the length of its side of the head, situated about 2/3 its own length from mandibular insertion.

Clypeal lobe distinctly projecting but short, rectangular, more than twice as broad as long, with parallel sides, a nearly straight anterior margin, and subrectangular free corners (in Wau Creek series, anterior margin weakly convex, free corners more rounded). Labrum with the transverse ridge feebly sinuate in front view, lacking a median tubercle; labrallobes each with a small upturned apical tooth. Maxillary palpi each 3-merous; basal segment broadest, with one subapical lateral sensillum; apical segment with a single apical sensillum. Labial palpi each with 3 subequal segments; basal segment with 2 adjacent submedian sensilla; II with one subapical lateral sensillum; III with the same, plus 2 apical sensilla.

Mandibles stout, gently bowed, each with two small teeth at apex, a blunt tooth near apical quarter of ML, a large, blunt submedian tooth, and a distinct but rounded basal angle. Oblique groove at base continued as a broad lateral-marginal groove (strix) to apex.

Median frontal sulcus of head extends to or nearly to posterior quarter of head length. Scapes gently curved, moderately incrassate apicad, overreaching posterior border by more than their apical width when head is viewed full-face. Funiculus relatively slender, all segments longer than broad; apical segments not forming a club; pedicel (funiculus I) longer than II as 4:3.

Trunk robust, with a weakly convex dorsal profile as seen from the side; propodeum subequal in length to promesonotum; mesonotum convex, about half as long as propodeal dorsum, and separated from it by a distinct but only moderately impressed metanotal groove. Propodeal dorsum only very feebly convex, passing into declivity through a rounded obtuse angle. Declivity almost flat, with bluntly subangular lateral edges, densely punctate in upper 2/5, smooth and shining below this.

Petiolar node massive, subcuboidal, slightly higher and broader behind than it is long (disregarding sternital keel); front and rear faces flat, vertical, dorsal face gently convex and sloping slightly anteriad. Sternite forming a sharp, recurved (hook like) anterior subpetiolar process, followed by a short concavity and then by a long, low, feebly convex keel.

Postpetiolar segment (gaster I) wider than long (roughly about as 4:3) and very slightly wider than gaster II; anterior face abruptly vertical, its dorsal margin gently concave as seen from above. Gaster II (ignoring acrotergite normally covered by gaster I) longer than I, but still not quite as long as wide. In side view, these two segments are about equally high. Apical gastric segments short, as usual; sting very long (and is found extended up to 1.1 mm in some paratype workers), gently upcurved. Gonostylus (in paratypes) long, 2-merous.

Body basically smooth and shining, but sown with deep, conspicuous, piligerous foveolae, mostly round or oval on the head (here 0.03 to 0.09 mm in diameter), trunk and petiole, becoming more elongate axially on first two gastric terga. Foveolae on head smaller and more crowded, forming oblique chains interspersed with costulae between eyes and frontal lobes, but those caudad of eyes larger, forming vague, oblique chains, separated on the average by their diameters near the cephalic midline, but smaller and more crowded, often subcontiguous laterad and caudad. Foveolae more widely spaced on trunk and petiole, especially near midline and on sides of pronotum; metapleura with a few coarse longitudinal-oblique costae. Petiole and postpetiole (first gastric segment) with smaller, crowded foveolae on sides and ventrad, but on second gastric segment, the foveolae become very sparse apicad and ventrad, the surfaces here virtually smooth, except for a crowded band of small foveolae along the apical margin. Apex of gaster, antennal scapes, mandibles and legs prevailingly smooth, with spaced piligerous punctures.

Body and appendages clothed with numerous fine, tapered, decumbent to subdecumbent hairs, mostly each issuing from a foveola, and nearly all 0.10 to 0.25 mm long (up to 0.30 mm on anterior clypeal lobe).

Color rich, deep brownish red; legs a little lighter reddish.

Worker variation; apart from size, mainly involves slight differences among nest series in the shape of the median clypeal lobe (convex vs. straight apical margins), density and size of individual foveolae of sculpture, and depth of coloration.

Queen
Dealate, from holotype nest series, Wamuki: TL 8.2, HL 1.37, HW 1.50 (CI 109), ML 0.80 (MI 58), SL 1.20 (SI 80), EL 0.45, WL 2.61. Four additional queens range downwards in size slightly from this (Collection Nos. 887 (n = 3) and 990 (n = I) from Busu River, the smallest having HW 1.33. A female from the Wau Creek series is ergatoid, but has HW about 1.50; this specimen lacks ocelli, but has small, blackened forewing stumps. The queens resemble the workers except in the caste difference usual for ponerines.

Type Material
Described from material from four separate nest series, all from what is now Papua New Guinea: holotype from Wamuki, 800 m, on the Mongi River watershed, Huon Peninsula, 19-20 April 1955 (Wilson No. 844; MCZ). No; 844, a colony containing one queen and about 20 workers, was taken from a Zoraptera-stage rotten log in hill rain forest. Two colonies came from the area between the lower Busu and Bupu rivers, near Lae, at the base of the Huon Peninsula, in lowland rain forest (Wilson Nos. 887 and 990). No. 887 was a nest in a small Passalus-stage log, 28 April 1955, and included at least three queens. No. 990 was in a small (10 cm diameter) rotten log with interior crumbling, but bark intact. It held 50-60 workers, two queens, eggs, larvae up to half-grown (no larger larvae) and one cocoon. The brood chamber contained an unidentified insect larva, also an adult (cucujoid?) beetle that was still alive and feebly moving; this beetle could possibly have fallen or walked in during excavation of the nest. (Unfortunately, the residues from Wilson's collections were eventually lost.) The fourth collection comes from Wau Creek, at about 1200 m elevation in a “Stage III” [rotten] log (leg. D.H., A.C. and A.H. Kistner, No. 1213); it contained at least 10 workers and a more or less ergatoid queen.

Etymology
concava after the concave anterior face of the first gastric tergum

References based on Global Ant Biodiversity Informatics

 * Janda M., G. D. Alpert, M. L. Borowiec, E. P. Economo, P. Klimes, E. Sarnat, and S. O. Shattuck. 2011. Cheklist of ants described and recorded from New Guinea and associated islands. Available on http://www.newguineants.org/. Accessed on 24th Feb. 2011.
 * Willey R. B.; W. L., Jr Brown. 1983. New species of the ant genus Myopias (Hymenoptera: Formicidae: Ponerinae). Psyche (Cambridge) 90: 249-285.
 * Wilson Edward O. 1959. Adaptive Shift and Dispersal in a Tropical Ant Fauna. Evolution 13(1): 122-144