Stigmatomma Roger, 1859

Eguchi, Katsuyuki, Viet, Bui Tuan & Yamane, Seiki, 2014, Generic Synopsis of the Formicidae of Vietnam (Insecta: Hymenoptera), Part II — Cerapachyinae, Aenictinae, Dorylinae, Leptanillinae, Amblyoponinae, Ponerinae, Ectatomminae and Proceratiinae, Zootaxa 3860 (1), pp. 1-46 : 26

Stigmatomma Roger, 1859

Taxonomy. Yoshimura & Fisher (2012) studied the male characters of Amblyopone Erichson sensu Brown (1960) , and divided it into three genera: Xymmer Santschi , Amblyopone and Stigmatomma Roger. They concluded that all the Asian species previously placed in Amblyopone belong to Stigmatomma , which has no unique character condition in the male but is clearly defined based on the mandiblular structure of the worker (but see below). Morphology. Workers of the Vietnamese species have the following features (see also Schmidt & Shattuck 2014):

Worker monomorphic; head in full-face view usually subrectangular, with genal angle beside each mandibular insertion which is rarely developed well as a small, triangular spine; preoccipital carina weak or absent dorsally and laterally; frontal lobes present, narrowly separated by posteromedian portion of clypeus, or approximate to each other; frontal carina rarely present; antennal scrobe absent; antennal sockets in full-face view at least partly concealed by frontal lobe; anterior margin of clypeus usually with a series of dents (see below); mandible elongate, narrowly blade-like with pointed apex, without basal margin; masticatory margin with one or two rows (dorsal and ventral rows) of teeth; antenna 11- or 12-segmented; eye relatively reduced or absent; eye, if present, situated behind midlength of side of head; mesosoma in lateral view with a flat or weakly arched dorsal outline; promesonotal suture present and flexible; metanotal groove absent dorsally; propodeum unarmed; propodeal lobe low or almost absent; petiole essentially sessile, but rarely with a distinct short anterior peduncle; broadly attached to abdominal segment III, in lateral view without a free posterior face; subpetiolar process present; abdominal segment III with a free anterior face below helcium only; girdling constriction between abdominal segment III and IV moderate to weak; pygidium large, convex across, laterally and posteriorly unarmed; hypopygium often armed with a series of spines posteriorly; sting well developed.

Differentiation. The worker of Stigmatomma is somewhat similar to that of Myopopone , but in the latter a few apical segments of the antenna are distinctly flattened.

A single worker specimen of Stigmatomma sp. eg-4 (collected from a dry dwarf forest of southern central Vietnam) is morphologically very distinct from the other Vietnamese species. It lacks a series of dents on the anterior clypeal margin; instead it has a plate-like projection just dorsal to the junction between the clypeus and labrum. This feature seems to be equivalent to a diagnostic characteristic of the worker of Xymmer discussed by Yoshimura and Fisher (2012) which recorded a male of Xymmer from Thailand. In order to confirm the identity of Stigmatomma sp. eg-4, colony samples containing males may be needed.

Vietnamese species (11 spp.).

S. amblyops Karavaiev, 1935 . Type locality: Caûda, Cochinchine [Cau Da, Nha Trang]. S. crenata Xu, 2001 . Zry (Cat Tien).

S. quadratum Karavaiev, 1935 . Type locality: Poulo Dama [Quan Dao Nam Du, Kien Giang]. Zry (Cat Tien). S. sp. eg-1 [= sp. 6 of SKY in Eguchi, Bui et al. (2005)] (Cat Tien, Nui Chua, Phu Quoc, Tam Dao, Tay Yen Tu). S. sp. eg-2 (Ba Vi).

S. sp. eg-3 (Pu Mat).

S. sp. eg-4 (Nui Chua).

S. sp. eg-5 (Phu Quoc).

S. sp. eg-6 (Van Ban).

S. sp. eg-7 [sp. 11 of SKY in Eguchi, Bui et al. (2005)] (Ba Vi). S. sp. eg-8 (Bidoup-Nui Ba).

Bionomics. Stigmatomma spp. usually occur in well-developed forests but sometimes in forest edges. They nest under rotting logs, under stones, and in litter and soil. We often found their nests with remnants of small centipedes probably eaten by their larvae.