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 (1993a) 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).