Proceratium robustum

AntWiki - Where Ant Biologists Share Their Knowledge
Jump to navigation Jump to search
Proceratium robustum
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Proceratiinae
Tribe: Proceratiini
Genus: Proceratium
Species: P. robustum
Binomial name
Proceratium robustum
De Andrade, 2003

Proceratium robustum P casent0172128.jpg

Proceratium robustum D casent0172128.jpg

Specimen Label

The type specimens were collected in rainforest.

Identification

A member of the silaceum clade and resembling Proceratium gracile but differing from it, in the worker, by the following characters: hind tarsomere shorter, CI > 94 instead of < 93, SI < 65 instead of ≥ 69 and hairs of type (2) longer and denser.

Keys including this Species

Distribution

Australia: New South Wales.

Distribution based on Regional Taxon Lists

Australasian Region: Australia (type locality).

Distribution based on AntMaps

AntMapLegend.png

Distribution based on AntWeb specimens

Check data from AntWeb

Biology

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.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • robustum. Proceratium robustum De Andrade, in Baroni Urbani & De Andrade, 2003b: 356, fig. 140 (w.q.) AUSTRALIA.

Holotype worker from New South Wales, Australia, labeled: "NSW. Dorigo N. P., Glade, 2700 ft., rainforest,12.ii.1968, R. W. Taylor, ex rotting log, Australian National Insect Collection ", in ANIC; 3 paratype workers, same data and collection as the holotype.

Type Material

  • Holotype, worker, Glade, Dorrigo National Park, New South Wales, 2700 ft., Australia, 12 February 1968, Taylor,R.W., ANIC32-017672, Ants Vial 35-130, Australian National Insect Collection; rainforest, ex rotten log.
  • Paratype, 2 workers, Glade, Dorrigo National Park, New South Wales, 2700 ft., Australia, 12 February 1968, Taylor,R.W., ANIC32-017673, Ants Vial 35-130, Australian National Insect Collection; rainforest, ex rotten log.

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

The isolated gyne attributed to Proceratium robustum, besides coming from the same area as the workers, shares with the workers the integumental sculpture and the hairs of type 2 decumbent or appressed on the petiole and gaster, instead of suberect as in the majority of the Proceratium species. The thick tarsi of both castes also strongly support this attribution.

Description

Worker

Head almost as long as broad, with gently convex sides. Vertex in full face view weakly convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae broad and badly covering the antennal insertions. Lateral expansions of the frontal carinae broad, raised, diverging on the two anterior thirds, converging and carinate only on the posterior third. Frontal area concave and with a longitudinal carina prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a sulcus. Eyes visible as a dark dot below the integument, small and placed 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 6-10. Scapes short of the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 8-9 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 declivous posteriorly. Area between the basal and declivous faces of the propodeum dorsally gently concave, the concavity superficially carinate, the carina ending on each side in an angle. 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 anterolaterally weakly carinate. Ventral process of the petiole large, subtriangular and pointed posteriorly. Postpetiole slightly shorter than 1/3 of the gastral tergite I, with convex sides in dorsal view. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently 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 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 1/4 shorter than hind tibiae. Second tarsomere of hind legs slightly shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head reticulate-punctate and rugulose, the rugosities more longitudinal on the sides. Mesosoma punctate and with short, transversal rugosities on the middle of the mesonotum and of the propodeum. Petiole punctate, the punctures approaching granulation. Postpetiole, gaster and legs shining and with minute piligerous punctures.

Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, slightly longer on the postpetiole and gaster, sparser and erect on the funicular joints; (2) longer than type (1), sparse, subdecumbent on the head and mesosoma, decumbent or appressed on the petiole and postpetiole, subdecumbent or decumbent, denser on the gaster, absent on the antennae; (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, and the scapes with sparse hairs similar to type (2).

Colour. Light brown with slightly lighter scapes and legs.

Measurements in mm and Indices: TL 3.12-3.19; HL 0.72; HW 0.69-0.70; EL 0.04-0.05; SL 0.45-0.46; WL 0.88; PeL 0.22-0.23; PeW 0.31-0.32; HFeL 0.52-0.53; HTiL 0.42-0.46; HBaL 0.29-0.30; LS4 0.35-0.36; LT4 0.70; CI 95.8-97.2; SI 62.5-63.8; IGR 0.48-0.51.

Queen

(tentative attribution). Differing from the worker in the following details: eyes large, about 1/3 of the head length, composed by many facets and with ocular pilosity. Ocelli well developed.

Mesosoma robust and convex in side view. Parapsidal furrows marked. Scutellum with the sides gently convex and with the posterior border subtruncate. Dorsum of the scutellum with a longitirdinal carina prolonging to the posterior half of the mesonotum. Metanotum with a small pointed tooth. Basal face of the propodeum medially slightly more concave and laterally denticulate.

Posterior half of the mesonotum and scutellum with irregular, longitudinal rugosities.

Measurements in mm and Indices: TL 3.48; HL 0.72; HW 0.70; EL 0.23; SL 0.46; WL 1.06; PeL 0.25; PeW 0.35; HFeL 0.59; HTiL 0.46; HBaL 0.35; LS4 0.38; LT4 0.79; CI 97.2; SI 63.8; IGR 0.48.

Etymology

From the Latin robustus (= robust, sturdy), referred to stout body of this species.

References

  • 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 356, fig. 140 worker, queen described)