Taxonomic history
See also: Shattuck et al., 2012 PDF: 43.Holotype worker
HL, 0.56 mm.; HW, 0.39 mm.; SL, 0.34 mm.; CI, 70: SI, 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. General features as shown in figures 22 and 23. Habitus similar to the related species dammermani and 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.
Paratype workers
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.; CI, 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.; CI, 69, 67; SI, 86, 86; WL, 0.66, 0.68 mm.; PW, 0.27 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.
Paratype queens (figs. 2, 24, 25)
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; SI, 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 venation as in figure 2, similar to that of P. 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.
Paratype male
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 and shown in figures 26 and 27. 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.
Holotype Australia: Australian Capital Territory, Mt. Stromolo (type locality), 11. hi. 1933 (T. Greaves). Paratypes: 3 [[ worker ]] 4 [[ queen ]] 1 [[ male ]] same data as type; 2 Queensland, Greenmount, 4. xii. l 949 (T. Greaves).
The holotype, paratype male, and most paratype workers and queens are deposited in the Australian National Insect Collection, C. S. I. R. O., Canberra. Other paratypes are in the Museum of Comparative Zoology (1 [[ worker ]] 1 [[ queen ]]) and the National Museum of Victoria, Melbourne (1 [[ worker ]]).
Ecology. - The Mt. Stromolo 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.
Relationships. - Close to P. dammermani and P. salomonis , but differing from them in the form of the petiolar node and the relative proportions of the head and antennal scapes (see above under P. salomonis ).
