Eutetramorium

Forest dwelling species of ants, the genus is endemic to Madagascar and Comoros.

Identification
One of a number of closely related Myrmicinae genera - the Eutetramorium group - from Madagascar, species in the genus Eutetramorium superficially resemble Tetramorium.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Nomenclature

 *  EUTETRAMORIUM [Myrmicinae: Myrmicini]
 * Eutetramorium Emery, 1899f: 280. Type-species: Eutetramorium mocquerysi, by subsequent designation of Wheeler, W.M. 1911f: 163.

Bolton and Fisher (2014):

This small genus was established by Emery (1899) for two conspicuous, large, darkly coloured Madagascan species that superficially resemble Tetramorium. Initially, Emery (1912, 1914) was of the opinion that the genus was referable to the tribe Myrmecinini, but Ashmead (1905) and Wheeler (1910) had already referred it to Tetramoriini, an opinion that Emery (1915b, 1924) also came to accept. Bolton (1976) excluded Eutetramorium from Tetramoriini on morphological grounds, and tentatively transferred it to Myrmicini. This placement persisted until recently, when a molecular analysis of Myrmicini by Jansen & Savolainen (2010) showed that the monophyly of the tribe was dubious, and that Eutetramorium formed a clade with Huberia. The yet unpublished, more detailed, DNA analysis of Myrmicinae by Philip S. Ward has established that Eutetramorium belongs in a strongly supported, endemic Madagascan clade that also includes four other genera.

Worker
Monomorphic myrmicine ants.

Mandible triangular; masticatory margin with 6–8 teeth, longer than the basal margin.

Palp formula 4,3, or 4,2.

Stipes of maxilla with a coarse transverse crest.

Clypeus posteriorly moderately broadly inserted between the frontal lobes; median portion of clypeus broad, not bicari¬nate.

Clypeus with lateral portions raised into a shielding wall or sharp ridge in front of the antennal sockets.

Clypeus with a tooth or triangular point at midpoint of anterior margin; without an unpaired seta at the midpoint.

Frontal carinae restricted to frontal lobes, never extending to the posterior margin of the head.

Antennal scrobes absent.

Antenna with 12 segments, with an apical club of 3 segments; scape distinctly downcurved near its base.

Antennal socket and torulus subtended by a depressed antennal fossa; anterior margin of the fossa is formed by the pos¬terior surface of the narrow, raised, lateral portion of the clypeus.

Torulus with upper lobe concealed by the frontal lobe in full-face view. In profile the torulus lobe large, directed down¬ward over the condyle of the scape.

Eyes present, located slightly in front of, to slightly behind, the midlength of the side of the head capsule in full-face view.

Head capsule without a median, longitudinal carina.

Pronotal humeri rounded in dorsal view.

Metanotal groove impressed.

Propodeum bispinose or bidentate.

Propodeal spiracle behind midlength of sclerite.

Metasternal process present.

Tibial spurs: mesotibia 0 or 1; metatibia 0 or 1; simple when present.

Abdominal segment 4 (first gastral) tergite does not broadly overlap the sternite on the ventral gaster; gastral shoulders absent.

Sting simple, without a spatulate to pennant-shaped lamellate appendage that projects from the dorsum of the shaft near or at its apex.

Main pilosity of dorsal head and body: simple.

Queen
Extreme ergatoid in mocquerysi, alate in monticellii. In parvum a normal dealate queen is present in the type-series, but there is also a specimen that may be an ergatoid or a worker-queen intercaste, or possibly merely an oversized worker, as discussed under parvum. Dealate queen with characters as worker except for the usual modifications of the mesosoma and the presence of ocelli. Venation: see under male.

Male
Known only for E. mocquerysi. Smaller than conspecific worker. Mandible stoutly triangular, with 7 teeth. Palp formula 4,3. Stipital crest present on maxilla. Antenna with 13 segments, filiform. SI 31. First funicular segment short but not globular, about one quarter the length of the second funicular segment. In full-face view eye located in front of midlength of head capsule. Ocelli small, conspicuous. Occipital carina sharp but not forming a raised crest. Mesotibia and metatibia each with a single spur, barbulate on mesotibia, weakly pectinate on metatibia. Notauli weakly present, the anterior arms forming a V-shape. Mesoscutum anteriorly, between the notauli arms, with a longitudinal median carina that is narrowly bifurcated anteriorly. Mesopleuron with a marked transverse sulcus. Propodeum unarmed, the spiracle low on the side and in front of the midlength of the sclerite; propodeal lobes conspicuous, rounded. Petiole with a short, stout anterior peduncle and a short but relatively high node, the spiracle about level with the base of the anterior face of the node. Postpetiole greatly elongated, in profile almost twice the length of the petiole. Subpetiolar process present, small. Cerci present.

Forewing venation (based on male of mocquerysi and queen of monticellii). Rs·f4–5 does not meet R·f3 on anterior margin of wing (= marginal cell open). 2rs-m absent. 1m-cu present. Fusion of Rs+M extended distally, so that 1m-cu arises from Rs+M, not from M. Rs·f3 present (Rs+M divides into Rs·f3 and M·f3–4 proximal of the junction with 2r-rs). A·f2 long, not merely a stub distal of cu-a. In monticellii queens cu-a is retracted toward the wing base and arises from M+Cu, proximal of the point where it divides into M·f1 and Cu·f1–2. However, in the single mocquerysi male examined, cu-a arises at the point where M+Cu divides.