Crematogastrini

Eguchi, K., Viet, B. T. & Yamane, S., 2011, Generic synopsis of the Formicidae of Vietnam (Insecta: Hymenoptera), Part I - Myrmicinae and Pseudomyrmicinae., Zootaxa 2878, pp. 1-61 : 14

Crematogaster Lund, 1831

Taxonomy. The genus Crematogaster is assigned to the tribe Crematogastrini (Bolton 2003). Workers of Vietnamese species have the following features.

Worker monomorphic, but sometimes varying widely in size; head round, subrectangular or subtrapezoidal; frontal carina and antennal scrobe absent; median portion of clypeus roundly expanded anteriad, partly overhanging basal part of mandibles when fully closed; posteromedian portion very broadly inserted between frontal lobes; no isolated, median seta on anterior clypeal margin; mandible narrow; masticatory margin oblique, with 4 teeth; antennae 11-segmented, with a 2-, 3-, or 4-segmented club, or gradually incrassate; eye medium sized or rarely consisting of a few ommatidia; promesonotum more or less raised; promesonotal suture absent or weakly present dorsally; metanotal groove usually distinctly impressed, sometimes margined laterally by a longitudinal carina or lamella; propodeal spine usually (but not always) present, varying in size and shape; propodeal spiracle located well posteriorly on posterolateral margin of propodeum, just below base of propodeal spine; petiole depressed dorsoventrally, without node; postpetiole with rounded node which often bears median longitudinal impression, attached to dorsal surface of gaster; gaster in dorsal view triangular or cordate; sting spatulate.

Crematogaster is easily distinguished from all other myrmicine genera known from Vietnam by the morphology of the waist and gaster. The worker of species belonging to the subgenus Orthocrema of Crematogaster is a little similar to that of Recurvidris , but in the latter the propodeal spines are weakly to strongly recurved, the propodeal spiracle is located far in front of the base of the propodeal spine, the postpetiole, in dorsal view, is broadly attached to the first gastral segment, and the first gastral segment behind the postpetiole is extremely dorsoventrally compressed in lateral view. Antennal club is 2-segmented in Orthocrema , but 3-segmented in Recurvidris .

Vietnamese species. Three species have been described from Vietnam: agniae Karavaiev (type locality: Lien Chieu, Col de Nuage [Hai Van Pass, Hue Province]); brunnea subsp. latipetiolata Karavaiev (type locality: Cau Da); walshi st. bouvardi Santschi (type locality: Lang Bian). Furthermore, thirteen species have been recognized by us from Vietnam: aurita Karavaiev [= sp. eg-13] (Nui Chua); sewardi Forel [= sp. eg-14] (Nam Cat Tien); sp. eg-1 [= C. (Orthocrema) sp. 36 of SKY in Eguchi et al. 2005] (Ba Vi, Chua Yen Tu, Nam Cat Tien, Pu Mat, Sa Pa, Tam Dao, Tay Yen Tu, Van Ban); sp. eg-4 (Chua Yen Tu); sp. eg-6 (Ba Be, Ba Vi, Binh Chau-Phuoc Buu, Chua Yen Tu, Sa Pa, Nui Chua, Pu Mat, Tay Yen Tu); sp. eg-7 (Chua Yen Tu); sp. eg-8 (Ba Be); sp. eg-9 (Ba Be, Tay Ye n T u); sp. eg-10 (Sa Pa); sp. eg-12 (Van Ban); sp. eg-15 (Nam Cat Tien); sp. eg-16 (Nam Cat Tien); sp. eg-17 (Pu Mat).

Bionomics. Many species are arboreal foragers, and nest in decayed parts of standing trees and hollows of tree trunks and branches or build carton nests. Some species nest in soil or rotting logs on the ground. Species of the subgenus Orthocrema forage both on and under the ground.