This Collection of Hymenoptera is the most important contribution which has been made to the Aculeata through the exertions of Mr. Wallace; in point of geographical distribution, it adds much to our knowledge. In the Aru, Key, and neighbouring islands, we meet with the extreme range of the Australian insect-fauna; and as might be expected, it is found amongst the Vespidious Group, and in one or two instances in the Formicidae. The latter, being frequently conveyed from one island to another, can perhaps scarcely be considered indicative of natural geographical distribution. Of the forty-six species of the Formicidous Group, only six were previously known to science. Of the genus _Podomyrma_ here established, one species only, from Adelaide, was previously known; it is one of the most distinct and remarkable genera in the family. The _Pompilidae_ are species of great beauty, some closely resembling those of Australia in the banding and maculation of their wings; amongst the _Vespidae_ will be found some of the most elegant and beautiful forms in the whole of that protean family of Hymenoptera. Fam. ANDRENIDAE. Gen. PROSOPIS. 1. PROSOPIS MALACHISIS. _P._ nigro-caeruleo-viridis, nitida et delicatule punctata; alis hyalinis. _Female._ Length 4-1/2 lines. Deep blue-green, with tints of purple in certain lights, particularly on the head, the clypeus with a central longitudinal ridge, its anterior margin slightly emarginate; the flagellum rufo-piceous beneath, the ocelli white. Thorax: the wings hyaline and brilliantly iridescent; the legs dark rufo-piceous with a bright purple tinge. Abdomen delicately punctured, the head and thorax more strongly so; the latter with a semicircular enclosed space at its base, which is smooth and shining. _Hab._ Key Island. Gen. NOMIA. 1. NOMIA CINCTA. _N._ nigra, capite thoraceque punctatis, pedibus ferrugineis; segmentis abdominis apice fulvo-testaceo late fasciatis. _Female._ Length 5 lines. Black: the two basal joints of the flagellum, the apical margin of the clypeus, the labrum, mandibles, and legs ferruginous; the wings fulvo-hyaline, the nervures ferruginous, the tegulae more or less rufo-testaceous; the sides of the metathorax with tufts of pale fulvous pubescence and the floccus on the posterior femora of the same colour, the tibiae and tarsi with short ferruginous pubescence. Abdomen shining, the apical margins of the segments broadly fulvo-testaceous, very bright, having a golden lustre. _Hab._ Key Island. 2. NOMIA LONGICORNIS. _N._ nigra, lucida et delicatule punctata, facie pube brevi grisea tecta, femorum posticorum flocco pallido, tibiis externe fusco-pubescentibus; maris antennis, capite thoraceque longioribus.