Proceratium itoi

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Proceratium itoi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Proceratiinae
Tribe: Proceratiini
Genus: Proceratium
Species: P. itoi
Binomial name
Proceratium itoi
(Forel, 1918)

Proceratium itoi P casent0281853.jpg Proceratium itoi D casent0281853.jpg Specimen Label

A colony of P. itoi collected in Japan by Masuko and collaborators (1985) was formed of 202 workers and 1 queen. Workers are usually collected under stones and within the leaf-litter of glossy-leaved evergreen, deciduous broad-leaved and bamboo forests (Onoyama & Yoshimura 2002).

At a Glance • Larval Hemolymph Feeding  



A member of the itoi clade. Differing from the two ingroup species, Proceratium bhutanense and Proceratium malesianum, in the worker, by the palp formula 4,3 instead 3,2 and by the broader frontal carinae, from bhutanense only, by the presence of erect hairs over the whole body, and from malesianum only, by the mid basitarsi with hairs never as much as 1/2 of the mid basitarsal length.

Keys including this Species


China, Japan and Republic of Korea.

Distribution based on Regional Taxon Lists

Oriental Region: Taiwan.
Palaearctic Region: China, Japan (type locality), Republic of Korea.

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.

  • itoi. Sysphincta itoi Forel, 1918a: 717 (w.) JAPAN. Ogata, 1987: 107 (m.); Onoyama & Yoshimura, 2002: 35 (q.). Combination in Proceratium: Brown, 1958g: 247. See also: Baroni Urbani & De Andrade, 2003b: 267.

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



Baroni Urbani and de Andrade (2003) - Head longer than broad, its sides weakly convex. Vertex in full face view almost straight. Clypeus medially reduced, triangular, between and slightly longer than the antennal socket. Clypeal dorsum with a longitudinal carina. Antenna1 socket with broad torulus. Frontal carinae far (sic) each other, partially covering the antennal insertions. Frontal area behind the frontal carinae convex. Lateral expansions of the frontal carinae relatively narrow, raised, diverging. Genal carinae prominent. Eyes small, represented by a dark dot below the integument. Eyes on the midline of the head. First funicular joint subequal in length and width. Funicular joints 2-10 much broader than long. Last funicular joint about as long as the sum of joints 7- 10. Scapes clearly not reaching the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 3-4 denticles before the pointed apical tooth. Palp formula 4,3.

Mesosoma slightly longer than the maximum head length (mandibles included). Promesopleural and meso-melapleural sutures impressed ventrally only. Basal face of the propodeurn weakly declivous. Declivous face of the propodeum gently concave. Basal and declivous faces of the propodeum separate laterally by a weakly carinate angle. Sides of the declivous face of the propodeum carinate. Propodeal lobes surrounded by a narrow lamella. Propodeal spiracle round and above mid height in lateral view.

Petiole in profile with declivous anterior face and convex posteriorly. Petiole in dorsal view with diverging sides and convex posteriorly. Anterior border of the petiole variably concave and carinate, the carina dcnticulate on each side. Ventral process of the petiole small and triangular. Postpetiole anteriorly broader than the petiole; its sides diverging or gently convex. Postpetiolar sternite anteromedially with a weakly marked subtriangular projection. Postpetiolar sternite straight in side view. Constriction between postpetiole and first gastral segment impressed. Gastral tergite I strongly convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs slender but not very elongate. All tibiae with a pectinate spur. Spurs of fore legs without a basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 1/4 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia present.

Sculpture. Head, mesosoma, petiole and postpetiole granulate. First gastral tergite smooth and covered by piligerous punctures; its sides and the posterior border with additional granulation. Legs granulate, the granulation less marked than in the other body parts.

Pilosity. Body covered by hairs of three main types: (1) short, dense, subdecumbent on the whole body, sparse and suberect on the funicular joints; (2) longer than type (I), sparse, erect or suberect on the whole body, slightly shorter on the scapes, absent on the funiculi; (3) shorter than hair type (I), dense and decumbent on the funicular joints only. In addition the funicular joints bear whitish, thick, appressed, sparse hairs.

Colour brown.

Measurements in mm and Indices: TL 3.65-3.82; HL 0.81-0.83; HW 0.71-0.74; EL 0.03; SL 0.49-0.50; WL 1.00-1.04; PeL 0.32-0.35; Pew 0.31-0.32; HFeL 0.64; HTiL 0.53-0.56; MBaL 0.38-0.41; LS4 0.25-0.30; LT4 0.86-0.92; CI 87.6-89. I; SI 60.2-60.5; IGR 0.34-0.35.


Baroni Urbani and de Andrade (2003) - Differing from the worker in the following details: eyes about 1/5 of the head length and with well defined ommatidia. Ocular pilosity present. Ocelli present.

Mesosoma robust. Scutellum large; its sides converging into a convex posterior border. Basal face of the propodeum gently declivous posteriorly; dorsally medially incised and as flat as the declivous face; its sides subangulate and carinate. Metanotum without denticle. Propodeal lamellae narrower.

Measurements in mm and Indices: TL 4.46-4.62; HL 0.86-0.88; HW 0.78-0.8 1 ; EL 0.17; SL 0.5 1; WL 1.28- 1.32; ; PeL 0.38-0.40; Pew 0.37; HFeL 0.75; HTiL 0.61 -0.62; HBaL 0.46; LS4 0.36-0.38; LT4 1.10- 1.12; CI 90.7-92.0; SZ 57.9-59.3; ICR 0.33-0.34.


Head subequal in size or slightly broader than long. Vertex in full face view convex. Vertexal margin carinate. Clypeus dorsomedially convex. Frontal carinae thin, low, diverging posteriorly. Frontal area with a sulcus. Ocelli large. Compound eyes large and placed mostly on the anterior part of the head sides. Scapes reaching the anterior ocellus. First funicular joint about 1/4 shorter than second joint. Joints 2-12 longer than broad. Last funicular joint slightly longer than the sum of joints 10-11. Mandibles edentate and only with a pointed apical tooth. Palp formula 4,3.

Mesosoma robust. Pronotum and anterior third of rnesonotum almost perpendicular to the posterior two thirds of the mesonotum. Posterior two thirds of mesonotum almost flat. Parapsidal furrows marked. Scutellum slightly higher than the mesonotum; its posterior border round. Basal and declivous faces of the propodeum convex in side and dorsal view. Sides of the propodeum gently converging. Declivous face of propodeum laterally superficially carinate. Metanotum with a median tooth. Propodeal lobes round and partially lamellaceous. Propodeal spiracles small.

Petiole in profile declivous in the anterior third and convex in the two posterior thirds. Sides of the petiole convex in dorsal view. Anterior border of the petiole concave and laterally carinate. Subpetiolar process absent; petiolar sternite gently convex. Postpetiole anteriorly broader than the petiole; postpetiolar sides diverging posteriorly. Anterior border of the postpetiolar sternite with a superficial triangular "lip". Gastral tergite I large and convex in side view. Remaining gastral tergites and sternites slightly curved ventrally.

Legs as in the worker but more elongate. Hind basitarsi slightly shorter than hind tibiae.

Fore wings of our type 2, hind wings of our type 3 as defined in the description of the genus.

Genitalia as in Fig. 114.

Sculpture. Head irregularly reticulorugose. Mesosoma minutely granulopunctate, the granulation more superficial on the mesonoturn. Scutellum, propodeum and pleurae with additional, thin, irregular rugosities. Postpetiole and gaster smooth and with minute piligerous punctures. Legs minutely granulopunctate.

Pilosity as in the worker but with hairs of type (2) sparser on the petiole, postpetiole and gaster.

Colour. Back with lighter antennae and legs.

Measurements in mm and Indices: TL 3.63-3.74; HL 0.59-0.60; HW 0.61-0.64; EL 0.30-0.31; SL 0.33; WL 1.20-1.28; PeL 0.34-0.35; PeW 0.25-0.26; HFeL 0.76-0.79; HTiL 0.65; HBaL 0.58-0.60; LS4 0.48; LT4 0.84; CI 103.4-106.7; SI 55.0-55.9; IGR 0.57.

Type Material

Worker. Type locality. Tokyo, Japan Type materlal 3 syntype workers labelled "Sysphincta itoi" For, worker type, Tokio, Japan (Ito)" in Musee d'Histoire Naturelle Genève, examined.