Stigmatomma noonadan

The types were collected "in or on the ground in newly cleared secondary growth."

Identification
A. noonadan is readily distinguished from the only other known western Melanesian Amblyopone, Amblyopone australis, by the characters of its “stigmatommine habitus" (i.e., "double ranked" mandibular dentition and enlarged clypeal teeth, etc., see Brown, 1960). In addition, australis is larger (minimum known HW on New Guinea about 1.5 mm), and has an acute tooth on each inferior pronotal angle. The third known Melanesian species, Stigmatomma celatum (Solomon Islands), is much smaller (3 syntype workers in the MCZ collection have HL 0.69-0.71 mm; HW 0.60-0.63 mm) with minute genal teeth (maximally only about as large as the median clypeal denticles) and with the head evenly and rather finely shagreened. (Taylor 1965)

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

Nomenclature

 *  noonadan. Amblyopone noonadan Taylor, 1965a: 6, figs. 3, 4 (w.) NEW GUINEA (New Britain I.). Taylor, 1979: 826 (m.). Combination in Stigmatomma: Yoshimura & Fisher, 2012: 19.

Worker
The following description is based on the holotype and single paratype.

Dimensions (in mm, holotype cited first). TL c. 5.5, 6 mm; HL (including clypeal denticles) 1.04, 1.12; HW (immediately behind genal teeth) 0.96, 1.04; maximum scape length (excluding articular condyle) 0.64, 0.68; outside total length of mandible 0.85, 0.90; PW 0.58, 0.65; WL 1.38, 1.42; midline length of petiolar dorsum 0.49, 0.55; maximum petiolar node width 0.50, 0.57; postpetiolar length at midline 0.36, 0.40; maximum width of postpetiole 0.65, 0.73.

General habitus as in Figures. Head with occipital border feebly concave, sides feebly convex, converging posteriad; anterior corners with strong acute genal teeth, the inner edges of which are about as long as the maximum width of the mandibular shafts. Frontal lobes approximate, separated by a deep linear groove. Clypeal apron strongly convex, with eight small denticles; the four median ones closely approximate, less deeply separated from each other than from the more lateral denticles, their apices diverging from the midline; the innermost of the two lateral denticles on each side moderately large, triangular, separated from the median quartet by a gap equal to its width at base; the outer tooth large and blunt, its apex jagged, forming two or three indistinct cusps. Mandibles slender, their external margins feebly concave, each bearing ten acute, slightly recurved teeth. The two basal teeth simple, conical, the basalmost blunt, the second acute; the eight apical teeth arranged in four more or less separated pairs, in typical "stigmatommine" fashion; the dorsalmost tooth of each pair lies slightly distal to its partner; a distinct low reclinate tooth is present on the inner edge of the strong acute mandibular apex. The mandibular apices cross when the jaws are closed, leaving a triangular gap between the mandibular and clypeal teeth. Palpal formula maxillary 4: labial 3 (paratype dissected). Scapes slender, slightly incrassate; funiculus with 11 segments proportioned as in Figure 4. Eyes small, variable in size, maximum diameter 0.02 mm in holotype, 0.06 mm in paratype, with four and nine or ten indistinct facets, respectively.

Mesosomal profile as in Figure. In dorsal view this tagma is widest at the pronotum and strongly narrowed at the base of the propodeum. Pronotal dorsum almost flat, with marginate lateral borders; inferior angles of pronotum broadly rounded. Promesonotal suture flexible; mesonotum transverse; mesometanotal suture vestigial, represented only by a sculptural break between the subopaque mesonotum and the moderately shining propodeum. Propodeal dorsum about as long as broad, its sides diverging posteriad; declivity feebly concave, rounding into dorsum, its lateral edges slightly raised, forming angles of a little more than 90 degrees in dorsal view.

Petiole sessile, its profile as in Figure; subpetiolar process afenestrate; nodal dorsum slightly wider than long in dorsal view, the anterior border with a slight median emargination, the sides converging slightly anteriad. Postpetiole wider but shorter than node, and also shorter than the succeeding segment which is of about the same width. Gastric apex laterally compressed, sting stout. Tibial spurs vestigial on middle legs; posterior tibiae each with a broad flat pectinate spur and a more slender simple conical one.

Mandibles and frontal lobes obscurely longitudinally striate. Clypeal apron with somewhat radial longitudinal striae; lateral parts of clypeus similarly sculptured, the striae on each side radiating back from a focal point at about the level of the inner basal edge of the mandible. These lateral clypeal striae arch back over the cheeks, where those nearest the midline are almost longitudinal, reaching back to the base of the frontal carinae; the cheek striae become increasingly divergent towards the sides of the head and the most lateral ones gather apically, at the base of the genal tooth. Remainder of head coarsely and roughly punctate-rugose; the sculptural trend faint, mainly longitudinal, but transverse across a narrow posterior strip. Scapes finely shagreened. Postgenae somewhat obscurely and irregularly longitudinally striate, the striae diverging posteriad. Lateral parts of the dorsa of the pronotum and propodeum with scattered punctures, about 0.02 mm in diameter, separated by about twice this distance on pronotum and more widely spaced on propodeum; a narrow longitudinal median strip on these sclerites lacks punctures, the surface here is shining, with a very fine superficial scale-like surface pattern which is also present on the interpunctural areas of the lateral strips, and which has a transverse trend on the posterior propodeal dorsum. Mesonotum subopaque, coarsely and irregularly shagreened.

Sides of mesosoma, except metepisternal area, subopaque, bearing somewhat effaced and polished, almost vertical fine striae, which are slightly curved (concave anteriorly) and slope posteriorly; sculptural intensity diminishing posteriad, with striae virtually absent behind the propodeal spiracle. Metepisternal area longitudinally striate. Declivity of propodeum shining, with very superficial, minutely scale-like transverse sculpturation. Petiolar dorsum subopaque, with scattered fine piligerous punctures; gastric tergites similar, the punctures finer and more abundant.

Pubescence adpressed and subadpressed, generally distributed over body except for the post-pronotal sides of the mesosoma and the sides of the petiolar node. Erect pilosity moderately abundant, especially on the dorsum of the body and towards the gastric apex, where the hairs are longest. Ground color dark chocolate brown, with the following areas infuscated with reddish brown: clypeus, frontal lobes, anterior corners of head, including genal teeth, pronotal collar, area of mesosomal-petiolar junction, subpetiolar process, posterior edges of gastric tergites, and gastric apex. Mandibles, antennae, legs and sting rich golden brown.



Type Material
Territory of New Guinea: New Britain: Yalom, 1,000 m, May 19, 1962 (Danish Noona Dan Expedition). The types were collected "in or on the ground in newly cleared secondary growth," no collector specified. The holotype is deposited in the Universitetets Zoologiske Museum, Copenhagen, Denmark; the paratype is in the Museum of Comparative Zoology (Type No. 31148).

Etymology
The species is named, in apposition, for the Danish expedition vessel Noona Dan.