_Gen. Char._: HEAD transverse, convex, glabrous; _ocelli_ placed in a triangle on the vertex, which is, as well as the face, convex; _antennæ_ short, subclavate, each inserted in a separate deep cavity in the centre of the face, the first joint of the flagellum globose, the second the longest of all and slender at its base, but all gradually enlarging to the extremity; _clypeus_ very gibbous; _labrum_ quadrate, convex; _cibarial apparatus_ long; _tongue_ long and tapering, and with a minute knob at its extremity; _paraglossæ_ obsolete; _labial palpi_ three-fourths as long as the tongue, the two first joints membranous and diminishing in width, the second joint rather shorter than the basal one and acute at its extremity, and externally before its termination the two very short terminal ones are inserted; _labium_ half the length of the tongue, with a lozenge-shaped inosculation; _maxillæ_ as long as the tongue, broad at the base, whence it abruptly acuminates to the slender apex; _maxillary palpi_ six-jointed, filiform, the three first joints subequal, the three terminal gradually decreasing in length. THORAX oval, glabrous; _prothorax_ inconspicuous; _mesothorax_ with a central basal groove, the _bosses_ conspicuous and shining; _scutellum_ and _post-scutellum_ lunulate; _metathorax_ subtruncate; _wings_ with three submarginal cells and a fourth slightly commenced, the second in the form of a truncated triangle, the third considerably larger than the second, and each receiving a recurrent nervure just beyond the centre; _legs_ plumose but not densely so, the hair very long within the posterior tibiæ, but denser and shorter on its exterior; the _posterior plantæ_ also plumose, and all the joints of the posterior tarsi conterminous; _claws_ bifid. ABDOMEN glabrous, subclavate, very convex above and flat beneath, subtruncate at the base, and the basal segments slightly constricted. The MALE scarcely differs, excepting in the _clypeus_ being less gibbous, the _legs_ not plumose, and the sixth segment of the _abdomen_ carinated in the centre towards its extremity, and impending over the seventh, which is transversely gibbous, then depressed, and with an obtuse process at its extremity. NATIVE SPECIES. 1. _cærulea_, Villers, ♂ ♀. 2-3 lines. (Plate VII. fig. 3 ♂ ♀.) _cyanea_, Kirby. 2. _albilabris_, Fabricius, ♂ ♀. 2½ lines. GENERAL OBSERVATIONS.