Proceratium relictum

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Proceratium relictum
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Proceratiinae
Tribe: Proceratiini
Genus: Proceratium
Species: P. relictum
Binomial name
Proceratium relictum
Mann, 1921

Proceratium relictum P casent0194740.jpg

Proceratium relictum D casent0194740.jpg

Specimen Label

Mann collected several females and a solitary worker under stones on Taveuni. The recent survey recovered workers from both Taveuni and Vanua Levu. Several dozen males were captured in malaise traps, all from either Taveuni or Vanua Levu, and it would appear that this species is restricted to those two northern islands. (Sarnat and Economo 2013). It has been collected from a range of habitats, including rainforest, disturbed forest and a forest edge garden.


A member of the silaceum clade.

Hita Garcia et al. (2015) - The following combination of characters separates P. relictum from the remainder of the Proceratium silaceum clade: comparatively large species (HW 1.03; WL 1.38); in full-face view head approximately as long as wide (CI 101); lateral expansions of frontal carinae weakly triangular and moderately rounded; petiolar node extremely squamiform (DPeI 620) and strongly narrowing from base to apex; subpetiolar process thickly spiniform.

Proceratium relictum and Proceratium oceanicum form a very close species pair easily distinguishable from the new species Proceratium vinaka and all other Proceratium species by the extremely modified petiolar node. Detailed information on how to separate P. relictum from P. oceanicum is presented in the species account of the latter and the identification key.

Baroni Urbani and de Andrade (2003) - Proceratium relictum is the largest of the three Proceratium species in Fiji, and can be separated from the closely related Proceratium oceanicum by its larger size, submarginate propodeal angels, and tooth-like subpetiolar process. (Sarnat and Economo 2013)

Keys including this Species


Distribution based on Regional Taxon Lists

Indo-Australian Region: Fiji (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 New General Catalogue, a catalogue of the world's ants.

  • relictum. Proceratium relictum Mann, 1921: 413, fig. 3 (w.q.) FIJI IS. See also: Baroni Urbani & De Andrade, 2003b: 306.

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



TL 5.09; HL 1.12; HW 1.10; EL 0.03; SL 0.87; WL 1.48; PeL 0.28; PeW 0.52; WFeL 1.10; HTiL 0.82; HBaL 0.74; LS4 0.54; LT4 1.12; CI 98.2; ST 77.7: IGR 0.48.

Baroni Urbani and de Andrade (2003) - Head about as broad as long and with the sides gently diverging posteriorly. Vertex in full face view straight. Clypeus reduced and as long as the antenna] sockets. Anterior border of the clypeus truncate. Frontal carinae far from each other, not covering the antennal insertions. Lateral expansions of the frontal carinae broad, moderately raised, diverging on the two anterior thirds and parallel and lower on the posterior third. Frontal area flat on the two anterior thirds, concave on the posterior third and with a long, thin longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a deep sulcus. Eyes small and on the middle of the head sides. First funicular joint about 1/5 longer than broad. Funicular joints 2-10 slightly broader than long. Last funicular joint slightly longer than the sum of joints 7-10. Scapes short of the vertexal margin and gently thickening apically. Mandibles elongate. Masticatory margin of the mandibles with 7 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma convex anteriorly, sloping posteriorly and slightly longer than the maximum head length (mandibles included) in profile. Pronotal suture very weakly impressed. Propodeal suture superficially impressed. Basal face of the propodeum slightly convex. Declivous face of the propodeum gently concave anteriorly and flat posteriorly. Each side of the declivous face of the propodeum carinate and with a small tooth after the concavity. Propodeal spiracle round and above mid height in lateral view.

Petiole squamiform, compressed and carinate dorsally. Anterior border of the petiole straight, without neck and carina. Ventral process of the petiole triangular and pointed. Postpetiole anteriorly slightly protruding on the petiole; its sides diverging and gently convex posteriorly. Postpetiolar sternite anteromedially with a marked subtriangular projection. Postpetiolar sternite gently convex posteriorly in profile. Constriction between postpetiole and gaster impressed. Gastral tergite I about 1/3 longer than the postpetiole and slightly convex on the curvaiure. Remaining gastral tergites and sternites curved ventrally.

Legs slender and 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 1/10 shorter than hind tibiae. Second tarsomere of hind legs subequal in size to the pretarsus. Pretarsal claws simple. Arolia small but present.

Sculpture. Body moderately shining. Head punctate and sparsely rugulose, the rugulae thicker and denser on the sides. Mesosoma, petiole, postpetiole, gaster and legs covered by dense, minute piligerous punctures.

Body covered by hairs of three main types: (1) short, dense, subdecumbent on the whole body, sparse on the funicular joints; (2) longer than type (1), erect on the whole body, sparse on the scapes, 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. Dark reddish brown with lighter legs.

Hita Garcia et al. (2015) - (N=1). TL 4.45; EL 0.04; SL 0.78; HL 1.01; HLM 1.28; HW 1.03; WL 1.38; HFeL 0.98; HTiL 0.71; HBaL 0.67; PeL 0.83; PeW 0.52; DPeI 620; LT3 0.69; LS4 0.42; LT4 1.02; OI 4; CI 101; SI 77; IGR 0.41; ASI 148.


Baroni Urbani and de Andrade (2003) - Differing from the worker in the following details: eyes large, 1/5 of the head length, composed by many ommatidia and with ocular pilosity. Ocelli well developed. Funicular joints about as broad as long. Mesosoma robust and convex in side view. Parapsidal furrows weakly marked. Scutellum with the sides converging posteriorly and with the posterior border round. Metanotunl with a minute denticle.

Measurements in mm and Indices: TL 5.78-5.91; HL 1.12-1.16; HW 1.14-1.16; EL 0.22; SL 0.90; WL 1.76-1.80; PeL 0.30-0.32; PeW 0.60; HTiL 0.85; HBaL 0.82-0.83; LS4 0.64-0.67; LT4 140; CI 100.0-101.8; SI 77.6-80.3; IGR 0.46-0.48.

Type Material

Baroni Urbani and de Andrade (2003) - Somosomo, Fiji Islands. Type material: 1 worker and 7 gynes (syntypes) labeled:P "Somo Somo, Fiji, W. M. Mann, Proceratium relictum Mann Cotypes", in National Museum of Natural History and Museum of Comparative Zoology, all examined.