_Gen. Char._: HEAD transverse, flattish; _ocelli_ in an open triangle on the vertex; _antennæ_ geniculated, the basal joint of the flagellum as long as the second, and both subclavate, the rest of the joints short and equal; _face_ flat, slightly protuberant between the insertion of the antennæ, and distinguished from the clypeus by a suture; _clypeus_ transversely quadrate, slightly widening gradually to the apex, marginate; _labrum_ transverse, obovate, fringed with setæ; _mandibles_ broad at apex, tridentate; _cibarial apparatus_ short; _tongue_ broad, subemarginate and fringed with short hair; _paraglossæ_ very slightly longer than the tongue, their apex broadly rounded and fringed with hair; _labial palpi_ as long as the tongue, joints subequal, gradating in substance, subclavate; _labium_ about as long as the tongue, pyramidal at its apical inosculation; _maxillæ_ about as long as the tongue, slightly lanceolate, fringed with short hair; _maxillary palpi_ rather longer than the maxillæ, with six joints, the basal joint robust and slightly constricted in the middle, the third joint linear and the longest, the remainder gradually decreasing in length and substance. THORAX subquadrate; _prothorax_ transverse, linear, angulated at the sides; _mesothorax_ with its _bosses_ protuberant; _scutellum_ and _post-scutellum_ semilunulate; _metathorax_ abruptly truncate, and longitudinally carinated in the centre; _wings_ with two submarginal cells, a third slightly indicated, the first recurrent nervure springing from the extreme apex of the first submarginal cell, closely to the first transverso-cubital nervure, and the second closely before the termination of the second submarginal cell; _stigma_ of the wing large and distinct; _legs_ wholly destitute of polliniferous hair, the terminal joint of the tarsus as long as the two preceding; _claws_ bifid; ABDOMEN subtruncate at the base, subconical with a downward bias. The MALE differs in having the _mandibles_ distinctly bidentate, the external tooth acute; the _antennæ_ are very slightly longer and more curved, and their colouring is more intense and more widely distributed. These insects are glabrous, generally intensely black, dull on the head and thorax, but shining on the abdomen, and are more or less thickly punctured, and they are usually gaily marked with yellow, citron, or red, especially on the face, thorax, and legs. NATIVE SPECIES. 1. _annulatus_, Fab., ♂ ♀. 2½-3 lines. _annulatus_, Kirby. 2. _dilatata_, Kirby, ♂. 3 lines. (Plate I. fig. 2 ♂.) _Hylæus dilatatus_, Curtis. 3. _annularis_, Kirby, ♂ ♀. 2½-3 lines. 4. _hyalinata_, Smith, ♂ ♀. 2-3 lines. 5. _signata_, Panzer, ♂ ♀. 3-3½ lines. (Plate I. fig. 2 ♀.) _signata_, Kirby. 6. _cornuta_, Kirby, ♂ ♀. 3-3¼ lines. 7. _varipes_, Sm., ♂ ♀. 1½ lines. 8. _variegata_, Fab., ♂ ♀. 2-3 lines. GENERAL OBSERVATIONS.