Myrmoteras

Bui, Viet Tuan, Eguchi, Katsuyuki & Yamane, Seiki, 2013, Revision of the ant genus Myrmoteras of the Indo-Chiese Peninsula (Hymenoptera: Formicidae: Formicinae), Zootaxa 3666 (4), pp. 544-558 : 545-546

Key to the Myrmoteras species from the Indo-Chinese peninsula ( Vietnam, Myanmar and Thailand) based on the worker caste

Note: Surface sculpture and pilosity of the dorsa of the head and pronotum looks very differently depending on the condition of specimens. In some specimens the surface looks somewhat shiny but in others from the same colony it can look completely mat. The pubescence (minute appressed hairs) on the pronotal dorsum and gastral tergites is often abraded away to some extent, particularly in the mediodorsal area of the second tergite; more hairs may remain in the lateral area of the tergite. It is highly recommended to observe multiple specimens from the same colony. Mandibular teeth are counted from the apex of the mandible and exclude denticles between the teeth; the first (apical) to fourth teeth are generally distinctly longer than the subsequent teeth, although counts of the teeth are somewhat arbitrary (see Fig. 1 ).

1. Median portion of anterior margin of labrum transverse, without a pair of long trigger hairs. Apical part of mandible not bent; with mandible seen in profile first (apical) and second (penultimate) teeth located on the same plane; a relatively large denticle present between second and third teeth and between third and fourth teeth ( Fig.1 –A).................................................................................................. (subgenus Myagroteras ).... cuneonodum Xu

- Median portion of anterior margin of labrum more or less triangular, bearing a pair of long trigger hairs. Apical part of mandible bent ventrally; with mandible seen in profile first (apical) and second (penultimate) teeth located on different planes; small denticle absent between second and third teeth and between third and fourth teeth (denticle seen only in abnormal individuals) ( Fig. 1 –B,C)..................................................................... (subgenus Myrmoteras )... 2

2. Third tooth of mandible much shorter than second and fourth teeth, looking like a large denticle ( Fig. 1 –B). Dorsum of mesonotum transversely and finely striate. Smaller species with head width 0.88–0.94 mm .............. jaitrongi sp. nov.

- Third tooth of mandible much shorter than second tooth, but as long as or longer than fourth tooth ( Fig. 1 –C). Dorsum of mesonotum variously sculptured, with longitudinal rugae or irregular sculpture, or rarely transversely striate. Larger species with head width more than 1 mm ......................................................................... 3

3. Second gastral tergite with abundant appressed short pubescence; distance between hairs generally shorter than hairs; pubescence on pronotal dorsum also denser...................................................................... 4

- Second gastral tergite without pubescence or with much sparser appressed short pubescence; distance between hairs on average much longer than hairs; pubescence on pronotal dorsum much sparser......................................... 5

4. Almost entire dorsum of head densely and distinctly sculptured; pronotal dorsum punctate. Coxae, femora and tibiae brown to reddish brown; legs of same colour as mesosoma.............................................. tomimasai sp. nov.

- Posterior 1/3 of head dorsum nearly smooth, with more superficial sculpture than in anterior 2/3, or dorsum of head extensively weakly sculptured; pronotal dorsum nearly smooth and shiny. Mid- and hind coxae creamy to yellowish; legs yellowish, much paler than mesosoma.................................................................. binghamii Forel

5. Median portion of clypeus and area just above clypeus nearly smooth and shiny; sculpture if any superficial. Mandible clear yellow; petiole tinged with yellow. Frontal sulcus confined to median portion of head, not reaching median ocellus............................................................................................. namphuong sp. nov.

- Clypeus and lower frons distinctly and densely sculptured. Mandible yellowish to dark brown; petiole not tinged with yellow. Frontal sulcus very weakly developed, or distinct and usually reaching median ocellus............................... 6

6. Body and legs brown to dark brown; mandible, antenna and legs paler; femora of all legs of almost same colour as tibiae. Gastral tergite 2 almost without pubescence (rarely with very sparse pubescence). Frontal sulcus distinct, usually reaching median ocellus................................................................................ concolor sp. nov.

- Body brown, slightly with reddish tinge; mid- and hind coxae and femora whitish yellow; fore coxa and femur yellowish; femora of all legs distinctly paler than tibiae. Gastral tergite 2 with sparse pubescence (often abraded away). Frontal sulcus usually very weak............................................................................. opalinum sp. nov.

Figures

FIGURE 1. Left mandibles in dorsal view. A. Myrmoteras cuneinodum; B. M. jaitrongi; C. M. concolor.