Probolomyrmex greavesi

Probolomyrmex greavesi has been found in forested sites ranging from a non-native pine plantation through dry sclerophyll and into wet sclerophyll. It is known to nest in soil under rocks. It is one of the rarer Australian ants having been collected only a handful of times.

Identification
Petiolar node relatively short and broad and with the anterior and dorsal faces separated by a convexity; subpetiolar process forming a rounded 90° angle anteriorly and with the ventral margin straight; body large (HW > 0.35mm, ML > 0.65mm) and head broad (CI > 66).

Probolomyrmex greavesi is similar to Probolomyrmex latalongus (from Australia) and Probolomyrmex vieti (from Thailand, Vietnam and Indonesia). It differs from P. latalongus by its larger size (HW > 0.35mm and ML > 0.65mm vs. HW < 0.33mm and ML < 0.65mm in P. latalongus) and broader head (CI > 66 vs. CI < 66 in P. latalongus), and from P. vieti by the anteriorly angular and ventrally straight subpetiolar process (the process having an anterior tooth and concave ventral surface in P. vieti).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Taylor (1965) - The Mt. Stromlo material was collected under rocks in pine litter in a plantation of exotic Pinus radiata. The Greenmount material was taken in open Eucalyptus woodland, on a hill overlooking treeless downs. According to Mr. Greaves they were probably collected under a rock.

Nomenclature

 *  greavesi. Probolomyrmex greavesi Taylor, 1965d: 358, figs. 2, 22-27 (w.q.m.) AUSTRALIA. See also: Shattuck, Gunawardene & Heterick, 2012: 43.

Worker
Holotype. HL, 0.56 mm.; HW, 0.39 mm.; SL, 0.34 mm.; Cl, 70: Sl, 87; WL, 0.71 mm.; PW, 0.28 mm.; dorsal petiole width, 0.20 mm.; petiolar node index, 71 ; petiole height, 0.29 mm.; petiolar node length, 0.24 mm.; lateral petiolar index, 83. Habitus similar to the related species Probolomyrmex dammermani and Probolomyrmex salomonis. Cephalic proportions as in dammermani, occipital border almost straight, and sides of head slightly more convex. Eyeless. Scapes somewhat shorter than in either of the above species; basal funicular segment about one-third longer than broad, segments 2-10 broader than long, second subequal in length to third; apical segment slightly longer than the three preceding together. Mandible with an acute apical tooth followed by a series of seven or eight small denticles, anterior one of which is very slightly enlarged.

Mesosoma as in P. dammermani. Petiolar node shorter than in either dammermani or salomonis, its posterior border almost perfectly straight when viewed from side or from above. Subpetiolar process well developed, subrectangular; its anteroventral angle narrowly rounded, posteroventral _one produced as a small posteriorly directed tooth; lower edge feebly concave, almost straight.

Subopaque, sculpturation as in P. dammermani, punctural component somewhat less distinctly incised, almost lacking on mesosomal dorsum. Pubescence and pilosity as in dammermani.

Body medium-light golden-brown; antennae, legs and apex of gaster a shade lighter.

Paratypes. Three paratype workers, from same nest series as holotype, have the following dimensions: HL, 0.56-0.58 mm.; HW, 0.39 mm.; SL, 0.33-0.34 mm.; Cl, 67-70; SI, 85-87; WL, 0•73-0.76 mm.; PW, 0.29 mm.; dorsal petiole width, 0•19-0.20 mm.; petiolar node index, 66-69; petiole height, 0.30 mm.; petiolar node length, 0.25 mm.; lateral petiolar index, 83. Palpal formula, maxillary 4: labial 2 (dissected), general proportions of palp segments as in P. angusticeps. No significant structural variation shown among these specimens.

Two additional paratype workers from Greenmount, south Queensland, are smaller than those from type nest, but resemble them in all apparently significant characters: HL, 0.52, 0.55 mm.; HW, 0.36, 0.37 mm.; SL, 0.31, 0.32 mm.; Cl, 69, 67; SI, 86, 86; WL, 0.66, 0.68 mm.; PW, 0.27 mm.; dorsal petiole width, 0.17, 0.18 mm.; petiolar node index, 67, 67; petiole height, 0.27, 0.28 mm.; petiolar node length, 0.22, 0.23 mm.; lateral petiolar index, 82, 82.

Shattuck et al (2012) - Body light ferruginous brown. Head in full-face view with weakly convex sides and very shallowly concave occipital border. Eye absent. Antenna relatively short. Dorsal outline of mesosoma straight; posterior margin of dorsum of propodeum in dorsal view moderately concave; posterior face of propodeum separated from sides by an angle, the lamella being absent. Petiole including subpetiolar process higher than long, in profile with relatively steep anterior face and convex posterior outline; posterodorsal margin of petiolar node in dorsal view very weakly concave; subpetiolar process developed; its anteroventral portion forming a rounded 90° angle; posteroventral portion of subpetiolar process forming a blunt tooth; ventral surface straight. Abdominal segment III (gastral segment I) in profile relatively short, gently narrowed anteriad in the anterior 2/3; abdominal sternum III weakly convex behind the midlength.

(n=5)—CI 67–69; DPetW 0.18–0.20; HL 0.52–0.58; HTL 0.32–0.37; HW 0.36–0.39; LPetI 80–88; ML 0.66–0.77; PetH 0.26–0.29; PetNL 0.22–0.25; PronW 0.26–0.28; SI 83–90; SL 0.31–0.35.

Queen
Paratypes. Four queens present in type nest series: a rather worn, large headless specimen (probably the colony mother-queen), two winged ones and a little-worn dealate (all apparently virgins). These specimens have the following dimensions (those of the headless specimen cited last where applicable). HL, 0.54-0.56 mm., HW (behind eyes), 0•38-0.40 mm.; SL, 0.33 mm.; CI, 69-71; Sl, 83-87; WL, 0.74-0.75 mm., 0.77 mm.; mesonotal width, 0.29, 0.30 mm.; dorsal petiole width, 0.17-0.18 mm., 0.20 mm.; petiole height, 0.27-0.28 mm., 0.30 mm.; petiolar node length, 0.20-0.22 mm., 0.24 mm.; lateral petiolar index, 74-79, 77. Differing from worker in the usual characters. Maximum diameter of compound eye 0.11 mm., ocelli small. Details of antennal, mandibular and palpal structure as in worker. Mesosoma structurally complete. Form of petiole and gaster as in worker. Wing similar to that of Probolomyrmex angusticeps.

Sculpture, pubescence, pilosity and colour of body and appendages as in worker; eyes black, each ocellus with an adjacent black spot, mesosomal suture lines faintly infuscated, wings clear, their veins pale yellow, pterostigma pale brown.

Male
Paratype. A single specimen from the greavesi type nest series is the only known male of Probolomyrmex.

HL, 0.47 mm.; HW (across eyes), 0.49 mm.; SL, 0.38 mm.; WL, 0.84 mm.; mesonotal width, 0.39 mm.; dorsal petiole width, 0.14 mm.; petiole height, 0.18 mm.; petiolar node length, 0.22 mm. General characters as discussed in the generic diagnosis above. Compound eyes large, finely faceted, their maximum diameter 0•23 mm. Ocelli very large, their average diameter about 0.05 mm. Palpal segmentation, maxillary 4: labial 2 (dissected), proportions of palpomeres almost exactly as in worker. Basal and declivitous faces of propodeum forming an even curvature in side view; declivitous face very slightly concave in dorsal view, with weak, obtuse posterolateral lamellae. Propodeal spiracle directed posteriorly, area behind it slightly concave.

Mandibles antennae and frontoclypeal process finely punctate. Head and mesosomal dorsum subopaque, fairly coarsely shagreened. Sides of mesosoma more lucid, with fairly close, fine puncturation, which is almost effaced on parts of mesanepisternum. Declivitous face of propodeum smooth and shining. Petiole and gaster subopaque and indistinctly sculptured with a partly effaced, dense, medium puncturation, which is finer on node than gaster.

Colour dull dark reddish-brown. Mandibles, antennae, legs and terminalia yellowish-brown. Eyes black. Wing veins light yellowish-brown: pterostigma slightly darker.

References based on Global Ant Biodiversity Informatics

 * Andersen A. N., M. Houadria, M. Berman, and M. van der Geest. Rainforest ants of the Tiwi Islands: a remarkable centr of endemism in Australia's monsoonal tropics. Insectes Sociaux 59: 433-441.
 * Taylor R. W. 1965. A monographic revision of the rare tropicopolitan ant genus Probolomyrmex Mayr (Hymenoptera: Formicidae). Transactions of the Royal Entomological Society of London 117: 345-365.
 * Taylor R. W. 1987. A checklist of the ants of Australia, New Caledonia and New Zealand (Hymenoptera: Formicidae). CSIRO (Commonwealth Scientific and Industrial Research Organization) Division of Entomology Report 41: 1-92.