Orectognathus szentivanyi

Wilson found the first workers (No. 839) foraging on bushes or small trees under 2 m. tall, at about noon on a sunny day, but in deep shade in rain forest. Careful search of the ground litter below the bushes turned up two dealate females and additional workers, indicating that the nest was inadvertently scattered. The workers are very slow and deliberate in their movements, and often stand still in one spot for long periods. One worker was seen walking with gaster recurved under the alitrunk. None was seen with prey, which could have been one of the numerous Collembola seen so commonly on stems and leaves of trees where the ants were taken. In a colony fragment returned to the United States alive, the female and four workers were exceedingly sluggish, and failed entirely to attack some entomobryid collembolans enclosed in a small nest with them in such a way that numerous contacts between springtails and ants were enforced. One egg was laid by the ants, but this disappeared within a few days. The colony appeared to be disorganized, and the adults spent much of their time resting on the glass cover forming the ceiling to their chamber. After two or three weeks, all adults had died. (Brown 1957)

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

Nomenclature

 *  szentivanyi. Arnoldidris szentivanyi Brown, 1958b: 18, figs. 1, 2 (w.q.) NEW GUINEA. Combination in Orectognathus: Taylor, 1977: 583. See also: Bolton, 2000: 25.

Worker
Holotype: TL 6.1, HL 1.38, HW 1.18 (CI 86), scape L 0.92, max. diameter of eye 0.27, ML 0.80 (MI 58), WI 1.66 (occipital lobes overlap pronotum about 0.17 mm., an amount duly subtracted from TL), petiole L in side view 0.83, postpetiole L 0.35, gaster L 1.25, propodeal spine L 1.12, gaster w 1.02, pronotal w 0.71 mm.

Form as shown for the paratype in figures. Occipital lobes each bordered dorsolaterally by a round-edged carina, indicated in the figures. Mesepisternum on each side extended as a shallow translucent lobe overlapping the upper posterior part of the ore coxa. Metapleural lobes rounded. Petiole very slender, gently arched, its anterior peduncle very slightly depressed, the nodal portion approximately circular in cross section.

Body generally smooth and strongly shining; underside of head with strong, crowded but separate foveolae; a few small, inconspicuous foveolae on dorsum of head in zone bordering occipital excision, but most of upper surfaces of occipital lobes with no more than small, widely-spaced punctures. Pubescence and pilosity absent from body generally, except for the sensory setae of labrum and mandibles, the short hairs at gastric apex, and a dilute reclinate pubescence of the antennae, legs and mouthparts, most noticeable toward the extremities.

Color rich medium brownish-red; vertex and a median area just behind .clypeus almost imperceptibly shaded; mandibles, antennae, legs and gaster clear yellow; mandibular apices, dorsolateral margins of occipital lobes, propodeal spines, and both nodes ferruginous yellow.

TL 5.9-6.4, HL 1.31-1.43, HW 1.12-1.23 (CI 85-87), ML 0.74-0.82 (MI 57-58), WL 1.59-1.75 mm. Color of head and alitrunk varies from light to rather dark reddish-brown; infuscation of vertex absent to fairly distinct. Propodeal spines vary slightly in length, angles of elevation and divergence, and in strength of their arch as seen from the side; in some specimens the tips are a little more strongly deflected ventrad than in others.

Queen
TL 6.5, HL 1.43, HW 1.28 (CI 90), ML 0.80 (MI 56), WL 1.76 mm. Similar to worker, with the female differences usual for dacetines. Compound eyes only slightly larger than in worker; ocelli small but distinct. Meso- and metanota together forming an abruptly raised dome, smooth and shining, with scattered small punctures. Propodeal spines straight (not gently arched as in worker), only the extreme tips slightly deflected ventrad. Sculpture, color and pilosity as in worker, except that punctures on dorsal surfaces of occipital lobes are more abundant and larger, more nearly foveoliform. The second female paratype has the propodeal spines very slightly arched as seen in side view, but still straighter than in any of the workers.

Type Material
The holotype was collected with seven worker and two dealate female paratypes at the village Ebabaang, altitude about 1400 m., in the Mongi Watershed, Huon Peninsula, New Guinea, April 18, 1955 (E. O. Wilson leg.). The seven worker paratypes MCZ, HNM,.