5. POLYRHACHIS LONGIPES. _P._ niger; flagelli dimidio apicali tibiisque anticis pallide ferrugineis, prothorace petiolique squamula bidentatis. _Worker._ Length 3 lines. Black; the head and thorax finely rugose; the antennae elongate, longer than the insect; the apical half of the flagellum pale ferruginous. Thorax rounded above, the sides not margined; two spines on the thorax anteriorly, two on the metathorax, and two on the scale of the petiole; the legs elongate, with the anterior tibiae ferruginous. Abdomen globose, sometimes rufo-fuscous, or the base obscurely rufous. _Hab._ Aru. 6. POLYRHACHIS SERRATUS. _P._ niger; capite thoraceque rugosis, abdomine dense punctato, squama petioli transversa, margine superno serrata. _Worker._ Length 2 lines. Black, with the antennae and legs ferruginous. Thorax oblong-quadrate or very slightly narrowed towards the metathorax, slightly convex above, not margined at the sides, the divisions not perceptible; the head and thorax rugose and pubescent. Abdomen globose, shining, and closely punctured; the scale of the petiole transverse above, produced into an acute spine on each side, the upper margin finely serrated, the lateral margins narrowed to their base, and having two or three small sharp spines. _Hab._ Aru. 7. POLYRHACHIS SCUTULATUS. _P._ niger, fortiter politus et lucidus, metathorace petiolique squamula dente longo curvato acuto in latere utroque, pedibus nigro-ferrugineis. _Worker._ Length 2-3/4 lines. Black and very smooth and shining; the legs dark ferruginous. Thorax: the disk expanded, slightly convex above, with the margins acute and curving upwards; the anterior margin transverse, rather wider than the head, with the lateral angles slightly curved forwards, and very acute; the lateral margins of the prothorax curved backwards and inwards; the margins of the mesothorax are rounded; the pro- and mesothorax highly polished above, forming an escutcheon-shaped disk; the metathorax opake, and sprinkled with a few short glittering hairs, armed posteriorly with two long very acute spines, divergent and directed backwards. Abdomen globose; the scale of the petiole with two long curved acute spines, directed backwards to the curve of the abdomen. _Hab._ Aru. 8. POLYRHACHIS MUCRONATUS. _P._ laevis, nitidus, niger; thorace spinis duabus crassis compressis acutis postice armato. _Worker._ Length 2-1/2 lines. Black, smooth, and shining, very delicately and indistinctly aciculate; the antennae beneath and the tibiae and femora obscurely ferruginous, the anterior and intermediate tibiae brightest; the apex of the mandibles ferruginous. Thorax transverse in front, or very slightly curved, with the lateral angles acute; the thorax is rounded above, and not margined at the sides; the metathorax armed with two long, stout, acute compressed spines; the spines divergent, as well as two on the scale of the petiole, which are long and very acute. Abdomen globose. _Hab._ Aru.