De Andrade, 2003
Nothing is known about the biology of Proceratium gigas.
A Proceratium species belonging to the silaceum clade and differing from all the other species of the clade, in the worker, by the following combination of characters: CI = 83.9, frontal carinae broad and strongly diverging, petiolar node thick, and erect long hairs sparse. Proceratium gigas shares with Proceratium hirsutum the broad, diverging frontal carinae, but gigas has sparser and shorter hairs and denser body sculpture. gigas resembles Proceratium gracile and Proceratium robustum for the shape of the gaster, strongly convex in profile. Among the 6 species of the silaceum group known from Australia, gigas is the largest one as exemplified by its TL = 3.72 mm (TL < 3.62 mm for the other 5 species).
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
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Very little is known about the biology of Proceratium ants. They nest in soil, rotten wood, under deep-set stones and, in a few cases, tree branches. For many species the nest consists of small rounded chambers hollowed out of soft rotten wood or in the soil. Toward the cooler limits of the range, particularly in North America, nests and foraging workers are found under deep set rocks instead of in rotten wood. The nest site is usually in forest shade, in old moist gardens, or similar habitats that are constantly moist. Some species of known to be egg predators of arthropods, especially of spiders.
Most Proceratium are relatively rare but this is not the full explanation for why they are not commonly collected. Colonies of most species are small. Based on anectdotal natural history information from a few species, it was once thought that most Proceratium would likely be found to have mature colonies that contain somewhere between 10 - 50 workers. Yet nests with more than 50, and in some cases up to 200, workers have been been reported. Besides small colonies, these ants also do not appear to forage in places where they are readily encountered.
Males and females are though to be produced in small numbers but we generally do not have enough data for colonies of any species to know what might be typical. Reproductive flights have been observered toward the end of the summer in some northern temperate areas. In these regions the nuptial flight occurs during the last half of August. Both sexes climb some distance from the nest entrance before taking flight. Workers too issue from the nest during the nuptial flight, as is often the case with otherwise cryptobiotic ants.
The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.
- gigas. Proceratium gigas De Andrade, in Baroni Urbani & De Andrade, 2003b: 360, fig. 141 (w.) AUSTRALIA.
- Holotype, worker, East end of Blackbutt Track, Dorrigo National Park, New South Wales, 710m, Australia, 28 Feb.-5 March 1980, A. Newton, M. Thayer, Museum of Comparative Zoology; subtropical rainforest.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Head longer than broad and with parallel sides. Vertex in full face view gently convex. Clypeus reduced and slightly longer than the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae broad and slightly covering the antennal insertions. Lateral expansions of the frontal carinae broad, raised, diverging on the two anterior fourths, converging on the third fourth, diverging and carinate only on the posterior fourth. Frontal area concave on the three anterior fourths and with a longitudinal carina starting from the last fourth and prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae distinct, each carina corresponding to the external border of a deep sulcus. Eyes visible as a dark dot below the integument, small and on the middle of the head sides. First funicular joint about as broad as long. Funicular joints 2-10 broader than long. Last funicular joint as long as the sum of joints 7-10. Scapes short of the vertexal margin and gently thickening apically. Right mandible with masticatory margin with 4 denticles before the pointed apical tooth and left mandible minutely crenulate and with preapical and apical teeth. Palp formula 2,2.
Mesosoma convex and about as long as the maximum head length (mandibles included) in profile. Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Area between the basal and declivous faces of the propodeum gently concave medially and with a dorsal carina ending in a small tooth on each side. Declivous face of the propodeum flat. Sides of the declivous face of the propodeum slightly marginate. Propodeal spiracle round and above mid height in lateral view.
Petiole rectangular and thick. Anterior border of the petiole straight and anterolaterally carinate. Ventral process of the petiole large, subtriangular and slightly pointed posteriorly. Postpetiole about 1/3 shorter than gastral tergite I, with gently diverging sides in dorsal view. Postpetiolar sternite anteromedially with a marked subround projection, convex posteriorly in side view. Constriction between postpetiole and gaster impressed. Gastral tergite I convex on the curvature. Remaining gastral tergites and sternites curved ventrally.
Legs slightly elongate. All tibiae with a pectinate spur. Spurs of fore legs without basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 1/5 shorter than hind tibiae. Second tarsomere of hind legs about as long as the pretarsus. Pretarsal claws simple. Arolia very small.
Sculpture. Head reticulate-punctate and rugulose. Mesosoma granulopunctate and with few, irregular rugosities, the rugosities more longitudinal on the pleurae. Petiole and postpetiole granulopunctate. Gaster and legs shining and with minute piligerous punctures, the punctures denser on the legs.
Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, sparser and erect on the funicular joints; (2) longer than type (1), sparse on the whole body, erect on the head and mesosoma, suberect or subdecumbent on the scapes, petiole, postpetiole, gaster and legs. absent on the funiculi; (3) shorter than hair type (1), dense and decumbent on the funicular joints only. In addition the funicular joints bear whitish, thick, appressed, sparse hairs.
Colour. Light ferrugineous with slightly lighter antennae and legs.
Measurements in mm and Indices: TL 3.72; HL 0.87; HW 0.73; EL 0.04; SL 0.60; WL 1.04; PeL 0.25; Pew 0.35; HFeL 0.68; HTiL 0.56; HBaL 0.45; LS4 0.40; LT4 0.80; CI 83.9; SI 68.9; IGR 0.50.
From the Latin gigas (= giant), referred to large size of this species.
- Baroni Urbani, C., de Andrade, M.L. 2003. The ant genus Proceratium in the extant and fossil record (Hymenoptera: Formicidae). Museo Regionale di Scienze Naturali, Monografie, 36, 1–492. (page 360, fig. 141 worker described)