Proceratium politum

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

Proceratium-politumL5.jpg

Proceratium-politumD5.jpg

Specimen Label

The holotype was collected in disturbed rainforest beside a stream.

Identification

A member of the silaceum clade. Proceratium politum and Proceratium caledonicum are the sole Proceratium species recorded from New Caledonia. They resemble each other by having a shining body and propodeal sides at most angulate. Differs from caledonicum, in the worker, by the much broader frontal carinae and by the shorter erect hairs.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Australasian Region: New Caledonia (type locality).

Distribution based on AntMaps

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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

Worker

Nomenclature

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

  • politum. Proceratium politum De Andrade, in Baroni Urbani & De Andrade, 2003b: 324, fig. 131 (w.) NEW CALEDONIA.

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

Description

Worker

Head slightly longer than broad and with the sides gently diverging posteriorly. Vertex in full face view gently convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae very broad and weakly covering the antennal insertions. Lateral expansions of the frontal carinae broad, little raised, diverging on the two anterior fourths, converging on the third fourth, subparallel and carinate only on the posterior fourth. Frontal area concave and with a thin longitudinal carina faintly prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae superficially marked but short, each carina corresponding to the external border of a superficial sulcus. Eyes visible as a dark dot below the integument, small and on the middle of the head sides. First funicular joint almost 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 6-10 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma weakly convex in profile and as long as the maximum head length (mandibles included). Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Area between the basal and declivous faces of the propodeum weakly concave and poorly angulate on each side. Declivous face of the propodeum sloping posteriorly. Sides of the declivous face of the propodeum submarginate. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and not very thick. Anterior border of the petiole straight and anterolaterally carinate. Ventral process of the petiole large, subtriangular and pointed posteriorly. Postpetiole 1/3 shorter than gastral tergite II. Postpetiole in dorsal view with the sides gently convex. 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 1/5 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Body shining. Head minutely punctate, the punctures denser and mixed with irregular reticulation-rugosities below the eyes. Mesosoma, petiole, postpetiole, gaster and legs with minute piligerous punctures smaller than those on the head. Petiole with sparse, minute granulation.

Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, suberect and sparse on the funicular joints; (2) longer than type (1), erect on the whole body, shorter than in cnledonicum, absent from 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) but shorter.

Paratype Specimen Labels

Colour. Ferrugineous-orange with slightly lighter legs.

Measurements in mm and Indices: TL 3.16-3.47; HL 0.69-0.74; HW 0.64-0.69; EL 0.04-0.05; SL 0.46-0.49; WL 0.91- 1.00; PeL 0.22-0.23; PeW 0.33-0.35; HFeL 0.54-0.57; WTiL 0.45-0.47; HBaL 0.35-0.38; LS4 0.35-0.39; LT4 0.69-0.76; CI 92.7-93.2; SI 66.2-66.6; 1GR 0.51.

Type Material

Holotype worker from New Caledonia labeled: "NEW CAL. Toili River, Col d'Amieu For. Stn. 21.35S, 165.47E, 21 Feb 1977 350 m, P. Ward, disturbed rainforest, beside stream", 1 paratype worker, same data and collection as the holotype Australian National Insect Collection.

Etymology

From the Latin politus (= smooth), referred to the integumental sculpture.

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 324, fig. 131 worker described)