Table of contents Abstract . 3 Introduction . 4 Materials and Methods . 5 LEPTOMYRMEX Mayr 1862 . 8 Synonymic list of extant species of macro-Leptomyrmex . 8 Description of the worker caste . 9 Description of queen . 14 Description of male . 14 Keys to the worker caste . 18 KEY TO AUSTRALIAN LEPTOMYRMEX WORKERS . 18 KEY TO NEW GUINEA LEPTOMYRMEX WORKERS . 22 KEY TO NEW CALEDONIAN LEPTOMYRMEX WORKERS . 23 Keys to males . 23 KEY TO AUSTRALIAN LEPTOMYRMEX MALES . 23 KEY TO NEW GUINEA LEPTOMYRMEX MALES . 24 Species accounts . 25 The macro-Leptomyrmex species . 26 Leptomyrmex cnemidatus Wheeler, stat. nov.. 26 Leptomyrmex darlingtoni Wheeler . 29 Leptomyrmex erythrocephalus (Fabricius) . 30 Leptomyrmex flavitarsus (F. Smith) . 33 Leptomyrmex fragilis F. Smith . 34 Leptomyrmex geniculatus Emery, stat. nov. 36 Leptomyrmex melanoticus Wheeler, stat. nov. 38 Leptomyrmex mjobergi Forel . 39 Leptomyrmex niger Emery . 40 Leptomyrmex nigriceps Emery, stat. nov. 42 Leptomyrmex nigriventris (Guérin 1831) . 42 Leptomyrmex pallens Emery . 44 Leptomyrmex puberulus Wheeler . 45 Leptomyrmex rothneyi Forel, stat. nov. 47 Leptomyrmex ruficeps Emery, stat. nov. 48 Leptomyrmex rufipes Emery, stat. nov. 50 Leptomyrmex rufithorax Forel, stat. nov. 53 Leptomyrmex tibialis Emery, stat. nov.. 55 Leptomyrmex unicolor Emery . 56 Leptomyrmex varians Emery . 58 Leptomyrmex wiburdi Wheeler . 60 † Leptomyrmex neotropicus Baroni Urbani . 62 Micro-Leptomyrmex . 62 General comments . 63 Conclusion . 63 Acknowledgements . 63 References . 66 Abstract The ants of the genus Leptomyrmex (Hymenoptera: Formicidae), commonly called ‘spider ants’, are distinctive members of the ant subfamily Dolichoderinae and prominent residents of intact wet forest and sclerophyll habitats in eastern Aus- tralia, New Caledonia and New Guinea. This revision redresses pervasive taxonomic problems in this genus by using a combination of morphology and molecular data to define species boundaries and clarify nomenclature. Twenty-seven Leptomyrmex species are recognized and are informally split into two groups: the macro-Leptomyrmex (21 species), and its sister group, the micro-Leptomyrmex (six species). Nine subspecies are elevated to species status: L. cnemidatus Wheeler 1915, L. geniculatus Emery 1914, L. melanoticus Wheeler 1934, L. nigriceps Emery 1914, L. rothneyi Forel 1902, L. ruficeps Emery 1895, L. rufipes Emery 1895, L. rufithorax Forel 1915 and L. tibialis Emery 1895. Nineteen new synonymies are proposed (senior synonyms listed first): L. cnemidatus Wheeler 1915 = L. erythrocephalus venustus Wheeler 1934 = L. erythrocephalus brunneiceps Wheeler 1934; L. darlingtoni Wheeler 1934 = L. darlingtoni fascigaster Wheeler 1934 = L. darlingtoni jucundus Wheeler 1934; L. erythrocephalus (Fabricius 1775) = L. froggatti Forel 1910 = TAXONOMIC REVISION OF GENUS LEPTOMYRMEX Zootaxa 2688 © 2010 Magnolia Press · 3.