Diacamma Mayr, 1862

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 : 30-31

Diacamma Mayr, 1862

Taxonomy. The genus Diacamma is assigned to the tribe Ponerini ( Bolton 2003). Morphology. Workers of Vietnamese species have the the following features (see also Schmidt & Shattuck 2014):

Worker monomorphic; head in full-face view elliptical, with a distinct preoccipital carina dorsally and laterally; frontal lobes horizontal, narrowly separated by posteromedian portion of clypeus, partly concealing antennal sockets; antennal scrobe absent; median portion of clypeus strongly and triangularly produced anteriad; mandible subtriangular, with ca 10–15 teeth on masticatory margin; antenna 12 -segmented; eye developed well, strongly convex, located around or a little before midlength of side of head in lateral view; mesosoma in lateral view with gently convex dorsal outline, or pronotum slightly raised; mesonotum present as a transverse strip between promesonotal suture and metanotal groove; mesopleuson defined dorsally by a conspicuous excavation (in ergatoid queen the excavation filled with gemma), and posteriorly with sulcus; propodeum elongate anteriad, unarmed; orifice of propodeal spiracle slit-like; propodeal lobe indistinct; apicoventral part of foretibia with a small simple spur behind a large pectinate spur; apicoventral part of mid tibia with a simple spur in front of a simple to barbulate spurs; apicoventral part of hind tibia with a simple spur in front of a large pectinate spur; pretarsal claws of hind leg simple, without inner tooth; petiole without anterior peduncle; petiolar node in lateral view thick, with convex anterodorsal face and vertical posterior face; posterodorsal margin armed with a pair of acute spines; subpetiolar process present; its anteroventral and posteroventral corners acutely produced; girdling constriction between abdominal segments III and IV relatively weak; abdominal sternite sternite III with a distinct anteroventral flange beneath helcium; sting well developed; head, mesosoma and waist strongly rugose.

Differentiation. The worker of Diacamma spp. are in general appearance somewhat similar to that of Leptogenys , but in the latter a conspicuous excavation is absent above mesopleuron, and pretarsal claws of the hind leg are armed with one to many teeth on the inner margin.

Vietnamese species ( 7 spp.).

D. longitudinale Emery, 1889 . Type locality: Cocincina [southern Vietnam]. Zry (Cat Tien). D. rugosum (Le Guillou, 1842) . Rad (nr. Ha Noi), Zry (Cat Tien). D. sp. eg- 1 (Ba Be, Ba Vi, Chua Yen Tu, Cuc Phuong, Ky Thuong, Pu Mat, Tam Dao, Tay Yen Tu, Van Ban). D. sp. eg- 2 (Hon Ba, Cat Tien).

D. sp. eg- 3 (Cat Tien).

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

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

Radchenko ( 1993 a) treated D. geometricum (F. Smith, 1857) as an independent species not a junior synonym of D. rugosum , and recorded it from Nghe An and Ha Noi.

The following subspecies were also described from Vietnam: D. rugosum gibbosum Karavaiev, 1935 ( type locality: Dalat, Lang Biang [Mt. Lang Bian, Lam Dong Prov.]); D. rugosum longiceps Santschi, 1932 [originally D. geometricum longiceps ] ( type locality: Ha Noi); D. rugosum ovale Karavaiev, 1935 ( type locality: Ba-Me-Thout, Prov. Danlac [Buon Ma Thuot, Dak Lak Prov.]).

Bionomics. Diacamma spp. usually occurs in wooded habitats. They usually nest in rotting logs, under stones, and in the soil around tree bases. Gastropod guests (Prosobranchia: Pupinidae , and Pulmonata : Subulinidae ) are often found inside nests of D. sculpturatum complex ( Eguchi, Bui & Janssen 2005).