Tetramorium Mayr , 1855 is one of the most diverse ant genera comprising more than 400 species worldwide (Bolton, 1995a). Modern taxonomic revisions of this genus were carried out by Bolton (1976, 1977, 1979, 1980) for all zoogeographical regions except for the Palaearctic Region.

Although tropical Tetramorium species have very diverse biologies (habitat requirements, food preferences, nesting habits, etc.) the bionomics of the Palaearctic species is more or less uniform. They build nests mainly in the ground, often with soil mounds, frequently under stones and, rarely, in rotten wood. Biology, distribution and the life cycle of Tetramorium caespitum ( López et al. 1990; López et al. 1992; Sanetra et al. 1999; Attygalle & Morgan 1984; Brian et al. 1967; Cammaerts & Cammaerts 2000, 2001; Gallé 1986; Sanetra & Buschinger 2000; Steiner et al. 2003) and related T. impurum ( Stäger 1929; Poldi 1963; Cammaerts et al. 1984; Steiner et al. 2003; Csösz & Markó 2004)have been very well studied but other Palaearctic Tetramorium species have been little represented other than faunistic surveys. Colonies of Palaearctic Tetramorium are sometimes inhabited by several tens of thousands of workers and generally they live in dry and warm or even hot habitats including steppes and steppe-like grasslands, semi-deserts or deserts.

The first taxonomic revision (Emery 1909) of the Palaearctic Tetramorium includes five species and about 20 infraspecific forms. Later several reviews of the genus from different parts of the Western Palaearctic were provided by Santschi (1927), Stitz (1939) and Kratochvíl (1944); many infraspecific taxa were described by other authors. More recently, data on Palaearctic Tetramorium were published in regional monographs or special taxonomic papers, including descriptions of several new species from Morocco (Cagniant 1997), Iberian Peninsula ( López 1991a, 1991b; López et al. 1992), South Europe (Bernard 1967), Balkans, Europe (Agosti & Collingwood 1987a, 1987b), Switzerland (Kutter 1977), North Europe (Collingwood 1979), Italy (Mei 1995; Sanetra et al. 1999), Germany (Schulz 1996; Seifert 1996), Poland (Radchenko et al. 1998), European part of the former Soviet Union and Caucasus (Arnoldi 1968; Radchenko & Arakelyan 1990), former Soviet Union (Radchenko 1992a, 1992b), Kazakhstan (Bursakov 1984), Turkmenistan (Dlussky & Zabelin 1985; Dlussky et al. 1990), Afghanistan (Pisarski 1967a, 1967b, 1969), Turkey (Poldi 1979), Saudi Arabia (Collingwood1985; Collingwood & Agosti 1996), China (Wang et al. 1988; Xu & Zheng 1994; Zhou & Jiang 1998), Japan (Imai et al. 2003). As a result, about 60 species and infraspecific forms of Tetramorium were recorded from the Palaearctic up to now, mostly from the southern part of the region.

Taxonomy. The genus Tetramorium is assigned to the tribe Tetramoriini (for a complete taxonomic history see Bolton 2003). The Oriental species were revised by Bolton (1976, 1977). Workers of Vietnamese species have the following features.

Worker monomorphic; head in full-face view subrectangular, with rounded posterior corners; frontal carina usually (but not always) long and distinct; antennal scrobe weak or absent; anteromedian margin of clypeus weakly convex, often with a weak emargination at midpoint, lacking any denticles or teeth; an isolated median seta absent; posteromedian portion of clypeus very broadly inserted between frontal lobes; lateral portion of clypeus modified into a distinct ridge or wall in front of antennal insertion; mandible triangular; masticatory margin with apical and 1 or 2 larger preapical teeth followed by some smaller teeth or minute denticles; palp formula 4,3; antennae 11- or 12-segmented, with 3-segmented club; basal rim of shaft of antennal scape often forming an enlarged lobe expanding ventrad; eye medium to large in size; mesosoma in lateral view weakly convex dorsad; promesonotal suture absent dorsally; metanotal groove absent; anterior part of mesopleuron forming a flange projecting over basal part of fore coxa; propodeal spine present, varying in size and shape; propodeal lobe well developed usually as a triangular lamella or spinose projection but sometimes as a subrectangular or round lamella; petiole pedunculate, with distinct node; a tiny denticle or process present on the anteriormost part of ventral face of peduncle (it is often concealed by mesopleuron and or hind coxa in lateral view); gastral shoulder distinct to absent; apex of sting with a small lamellate appendage; head and mesosoma usually strongly reticulate or rugoso-reticulate.

The worker of Tetramorium is similar to those of Rhoptromyrmex and Myrmica (for distingusihing characters see under the latter genera)

Vietnamese species. Four species have been described from Vietnam: indosinense Wheeler [= sp. eg-13] (Type locality: Ha Noi; other locality: Ba Vi); infraspinosum Karaviev (type locality: Cau Da); kieti Roncin (type locality: Vietnam); secure Roncin (type locality: Vietnam). An additional 21 species have recognized by us from Vietnam: flavipes Emery [= sp. eg-4; = sp. 39 of SKY: Yamane et al., 2003] (Ba Vi, Chua Yen Tu, Cuc Phuong, Nam Cat Tien, Phu Quoc, Pu Mat, Tay Yen Tu, Van Ban); kheperra (Bolton) [= sp. eg-9] (Ba Vi, Phu Quoc, Tay Ye n T u); lanuginosum Mayr [= sp. eg-17] (Ba Vi, Bac Kan, Tam Dao); nipponense Wheeler [= sp. eg-5] (Ba Be, Ba Vi, Cuc Phuong, Sa Pa, My Yen, Pu Mat, Tay Yen Tu, Van Ban); sp. eg-1 (Sa Pa); sp. eg-2 [= kraepelini Forel : Eguchi et al., 2005] (Ba Vi, Nam Cat Tien, Phu Quoc, Pu Mat, Tay Yen Tu); sp. eg-3 [= sp. 32 of SKY: Eguchi et al., 2005] (Ba Vi, Chua Yen Tu, Tam Dao, Tay Yen Tu, Van Ban); sp. eg-6 [cf. pacificum Mayr ] (Sa Pa, Pu Mat); sp. eg-7 (Sa Pa); sp. eg-8 (Ba Be); sp. eg-10 (Tay Yen Tu); sp. eg-12 (Ba Vi, Pu Mat); sp. eg-14 (Binh Chau-Phuoc Buu); sp. eg-15 [= bicarinatum (Nylander): Eguchi et al., 2005] (Tam Dao); sp. eg-16 [= smithi Mayr : Eguchi et al., 2005] (Ba Vi); sp. eg-18 [= walshi (Forel): Yamane et al., 2003] (Cuc Phuong, My Yen, Pu Mat); sp. eg-19 (Ba Be); sp. eg-21 (Cuc Phuong); sp. eg-22 (Nam Cat Tien); sp. eg-23 (Nam Cat Tien, Nui Chua); sp. eg-24 (Nam Cat Tien).

Bionomics. Tetramorium species inhabit various habitats such as open lands, grasslands, forest edges and well-developed forests. Their nests are usually found in rotting logs, twigs, wood fragments, under stones and in soil. Workers forage mainly on the ground.

Worker small, monomorphic. Antennae 12-jointed, with a 3-jointed club. Clypeus narrowed on the sides where its posterior margin is raised in the form of a short trenchant ridge or carina as the anterior border of the antennal socket. Frontal carinae rather far apart, usually continued back some distance and often the full length of the head as subparallel ridges forming the inner borders of scrobes or demiscrobes for the accommodation of the antennal scapes. Maxillary palpi 4-jointed; labial palpi 3-jointed. Eyes well developed; ocelli absent. Mandibles rather large, triangular, their apical border with a few large and several small teeth. Premesonotal suture indistinct, mesoepinotal suture more or less distinct; mesoepinotal constriction usually feeble; epinotum with two spines or teeth and episterna usually spined or dentate. Petiole with a short but distinct peduncle and the node large, subcuboidal, rounded above, rarely squamiform; the postpetiole usually broader than the petiole. Legs rather short, middle and hind tibiae with small, simple spurs. Head, thorax, and petiole sculptured, usually rugose or reticulate rugose.

Female resembling the worker, but somewhat larger. Pronotum usually very little exposed above; mesonotum and scutellum raised above the level of the pro- and epinotum, the latter with stouter and shorter spines than in the worker. Fore wing with one cubital, one discoidal, and a closed radial cell.

Male slightly smaller than the female, with 10-jointed, very exceptionally with 12- or 13-jointed antennae. Second funicular joint very long, representing a fusion of 4 joints. Head small, ocelli and eyes large. Mandibles small but dentate. Pronotum overarched by the mesonotum, which has distinct Mayrian furrows. Epinotum truncate and dentate. Wings as in the female.

This genus might be described as peculiar to the Old World, because nearly all the few species occuring in America ( T. caespitum , simillimum , and guineense ) are known to have been introduced by commerce. The group reaches its greatest development in the Ethiopian Region so far as the number of species, subspecies, and varieties is concerned. Arnold has included Triglyphothrix, Xiphomyrmex , and Decamorium as subgenera, but I have treated them as genera, though a few species with simple hairs may be assigned indifferently either to Tetramorium or Triglyphothrix. I have still further reduced the size of the genus Tetramorium by establishing a new genus , Macromischoides , for T. africanum and aculeatum (vide supra). The species of Tetramorium form moderately large colonies and nest in the ground, usually under stones or logs. One of the species, T. caespitum , has a remarkable distribution, ranging from Britain to Japan, around the shores of the Mediterranean, and reappearing at higher elevations on Mt. Kilimanjaro.

There is one native species of Tetramorium in California, T. spinosum (Pergande) , which occurs in open dry habitats of southern California, and one introduced European species, T. caespitum (Linnaeus) (the pavement ant), which is found in urban and agricultural areas of central and northern California. Both are ground-nesting, with generalist foraging habits. Four other non-native species, of tropical origin, have been recorded occasionally from the state.

Species identification: keys in Bolton (1979). Additional references: Astruc et al. (2001), Brown (1957d), Bruder and Gupta (1972), Knight and Rust (1990), Longhurst et al. (1980), Martinez (1993), Merickel and Clark (1994), Sanetra and Buschinger (2000), Steiner et al. (2005).

Tetramorium Mayr, 1855: Verh. Zool. Bot. Ges. Wien.5: 423.

Type-species: Formica caespitum L. ,1758: Syst. Nat., ed.10: 581.

Distribution: Palaearctic, Ethiopian, Oriental, Australian, Polynesian, Nearctic & Neotropical regions.

Key to species

1 Body length 2.5 mm, propodeal spines relatively longer (Fig.42) ....................... ........................... T. brevicorne Brondroit

- Body length 3.5 mm, propodeal spines short .......................................................2

2- Dorsum of head with a distinct median depression, propodeal spines short and acute (Fig.43)............ T. depressicepes Menozzi

- Dorsum of head without a median depression, propodeal armature tuberculate and blunt (Fig.44)............... T. salwaen.sp.

Differe seulement du genre Tetramorium proprement dit par ses antennes de 11 articles. Le metanotum est en general plus retreci, arme, sauf chez le X. smithi , de deux longues epines etroites, divergentes, dirigees en arriere et en liant. Chez le genre Tetramorium proprement dit, les epines sont plus courtes et plus verticales; de plus les angles inferieurs de la face declive du metanotum sont ordinairement transformes en dents ou en epines, ce qui n'est pas le cas chez les Xiphomyrmex .

A ce sous-genre doivent se rapporter les especes tortuosum Roger , sigmoideum Mayr, smithi Mayr, kellerin. sp. et peut-etre l´ Ochetomyrmex (?) auropunctatus Roger. Mon ami le Dr. Mayr m'ecrit que cette derniere espece ne peut etre rapportee a son genre Ochetomyrmex , a cause de la forme de l'epistome. Cependant a tous les autres egards elle en est bien rapprochee et me parait tout au moins former un passage du sous genre Xiphomyrmex au genre Ochetomyrmex .

[[ worker ]]. L. 2,2 a 2,4 mill. Tres semblable aux T. Schaufussii et Nassonowii , mais de taille bien plus petite, et avec le thorax plus robuste, plus large, faiblement convexe, a dos subdeprime et subborde. Le thorax et la tete sont subopaques, tres finement et assez densement reticulesponctues, avec une sculpture superposee mediocrement grossiere, assez faible et vague, reticulee sur le dos du thorax, longitudinalement ridee sur la tete et les cotes du thorax. Metanotum arme de deux dents sensiblement plus longues que chez le T. Nassonowii ou si l'on prefere de deux epines extremement courtes, beaucoup plus courtes que celles du T. Schaufussii . Dents lamelliformes metasternales fort courtes. Suture meso-metanotale comme chez le T. Schaufussii . Premier n oe ud du pedicule comme chez le T. Schaufussii , mais sensiblement plus eleve, plus arrondi au sommet, surtout devant, et encore plus court. Il est plus eleve que le 2 me n oe ud. Pedicule et abdomen lisses et luisants.

D'un roux jaunatre. Abdomen d'un brun rousseatre. Pattes et mandibules d'un jaune roussatre.

Pilosite et pubescence encore plus faibles que chez le T. Nassonowii. Du reste comme cette espece et comme le T. Schaufussii .

Amparafaravantsiv.

- [[ worker ]]. - Long. 3.8 mill. - Mandibules lisses, luisantes, avec de petits points epars, armees de 7 dents, dont les posterieures indistinctes. Epistome sans carene, echancre au milieu de son bord anterieur. Tete comme chez le guineense , mais bien plus large, a peine plus longue que large, distinctement retrecie devant. Massue des antennes plus grele, presque de 4 articles. Thorax, surtout le pronotum, bien plus large que chez le guineense et beaucoup plus convexe dans le sens longitudinal, subborde; echancrure meso-epinotale un peu plus forte. Epines superieures plus verticales, un peu plus courtes-, plus larges a la base, non courbees a l'extremite; dents inferieures plutot plus courtes N oe uds du pedicule plus epais, plus larges et plus arrondis que chez le guineense- Le premier n oe ud n'est pas tronque, mais arrondi devant, et forme avec son petiole anterieur une seule courbe anterieure concave sur le profil; il est aussi arrondi et bien moins tronque derriere.

Meme sculpture que. le guineense , mais plus serree, ' un peu plus.

fine et moins luisante; base de l'abdomen striee en long. Pilosite comme chez le guineense .

D'un rouge brunatre, comme la Myrmica laevinodis ; membres plus clairs; abdomen un peu plus terne, plus brun jaunatre; donc plus fonce que le guineense , sauf l'abdomen qui est au contraire plus clair.

Natal (Haviland). Tres voisin du guineense et pourtant nettement different; plus grand, plus robuste, avec les mandibules lisses, les epines differentes, ainsi que le 1 er n oe ud, etc. Etant donnee la grande constance du guineense , je suis d'avis qu'il s'agit d'une espece distincte. Autant que la description permet d'en juger, il differe de quadridentatum Stitz par ses courtes dents inferieures (episternales), par les mandibules lisses et par l'epistome echancre.

Se distingue des autres especes des Xiphomyrmex et des Rogeria par son enorme tete, par son exiguite, par son habitat nearctique et par ses teguments lisses.