Proceratium gracile

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Proceratium gracile
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Proceratiinae
Tribe: Proceratiini
Genus: Proceratium
Species: P. gracile
Binomial name
Proceratium gracile
De Andrade, 2003

Proceratium gracile casent0172097 profile 1.jpg

Proceratium gracile casent0172097 dorsal 1.jpg

Specimen labels

Nothing is known about the biology of Proceratium gracile.


A Proceratium species belonging to the silaceum clade and resembling Proceratium robustum but differing from it, in the worker, by the following characters: hind tarsomeres longer, CI < 93 (instead of > 94), SI ≥ 69 (instead of < 65) and the by the hairs of type (2) shorter and sparser.

Keys including this Species


Latitudinal Distribution Pattern

Latitudinal Range: -28.04999924° to -28.04999924°.

Tropical South

Distribution based on Regional Taxon Lists

Australasian Region: Australia (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


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.

  • gracile. Proceratium gracile De Andrade, in Baroni Urbani & De Andrade, 2003b: 353, fig. 139 (w.) AUSTRALIA (Queensland).
    • Type-material: holotype worker, 5 paratype workers.
    • Type-locality: holotype Australia: Queensland, Mt Cordeaux, Cunningham’s Gap, 3000 ft, 1.v.1962, Accession 722, ANIC ants vial 35-131, rotten wood, forest floor, rainforest (R.W. Taylor); paratypes with same data.
    • Type-depository: ANIC.
    • Distribution: Australia.

Type Material

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.



Head slightly longer than broad and with subparallel sides. Vertex in full face view gently convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae broad and partly 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 and with a longitudinal carina prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae superficially marked, each carina corresponding to the external border of a superficial sulcus. Eyes absent. 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 6-10. Scapes short of the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 5-6 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma gently convex and slightly shorter than maximum head length (mandibles included) in profile. Pronotal and propodeal sutures absent. Basal face of the propodeum gently declivous posteriorly. Area between the basal and declivous faces of the propodeum with a dorsal, faint, transversal carina. Each side between the basal and declivous faces of the propodeum subangulate. 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 subrectangular and not very thick. Anterior border of the petiole straight and weakly carinate anterolaterally. Ventral process of the petiole large, subtriangular and pointed posteriorly. Postpetiole about 1/4 shorter than gastral tergite I. Postpetiole in dorsal view with convex sides. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently convex posteriorly in profile. Constriction between postpetiole and gaster impressed. Gastral tergile I convex on the curvature, strongly convex after the postpetiolar constriction in dorsal view. Remaining gastral tergites and sternites curved ventrally.

Legs not very elongate. All tibiae with a pectinate spur. Spurs of fore legs without basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 1/6 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head reticulate-punctate rugulose. Mesosoma, petiole, postpetiole, gaster and legs superficially shining, minutely punctate to weakly granulate, the granulation less marked on the gaster.

Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, slightly longer on the gaster, sparser and erect on the funicular joints; (2) longer than type (1), erect and relatively sparse on the whole body, 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-brown with slightly lighter legs.

Measurements in mm and Indices: TL 2.98-3.27; HL 0.71-0.74; HW 0.65-0.68; EL absent; SL 0.49-0.52; WL 0.85-0.90; PeL 0.21-0.22; PeW 0.32-0.35; HFeL 0.52-0.56; HTiL 0.43-0.46; HBaL 0.36-0.40; LS4 0.30-0.35; LT4 0.61-0.72; CI 91.5-91.9; SI 69.0-70.1; IGR 0.48-0.49.

Type Material

Holotype worker from Queensland, Australia labelled: "QLD. Mt. Cordeaux, Gunning Hams Gap, 3000', 1.V.1962, R. W. Taylor, rtn. wood forest floor, rainforest, R. W. Taylor, Acession 722, Australian National Insect Collection Ants Vials 35-131", in ANIC, 5 paratypc workers, same data and collector as the Holotype.


From the Latin gracilis (= weak) as opposed to the species Proceratium robustum.


  • 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 353, fig. 139 worker described)