_Gen. Char._: HEAD transverse, as wide as the thorax, flattish; _ocelli_ placed in a very open curve upon the vertex; _face_ flat, but convex in the centre beneath the insertion of the antennæ; _clypeus_ very slightly convex; _labrum_ transverse, narrowly lunulate; _mandibles_ bidentate; _cibarial apparatus_ moderately long; _tongue_ very acute and fringed with delicate down; _paraglossæ_ barely half the length of the tongue, and acute, their apex fringed laterally with down; _labial palpi_ inserted in a deep sinus, filiform, the basal joint the longest, the rest diminishing both in length and substance; _labium_ about half the length of the entire organ, its inosculation emarginate; _maxillæ_ hastate, rather longer than the tongue; _maxillary palpi_ six-jointed, the basal joint the shortest, the third the longest, the remainder diminishing gradually in length, and all declining in substance from the basal joint. THORAX oval, rather pubescent; _prothorax_ transverse, curving to the mesothorax, whose _bosses_ are inconspicuous; _scutellum_ transverso-quadrate; _post-scutellum_ transverse linear; _metathorax_ truncated. WINGS with two submarginal cells, and a third commenced, the second about as long as the first, and receiving both the recurrent nervures, the first near its commencement, and the second nearer its extremity; _legs_ robust, with the posterior _tibiæ_ and _plantæ_ densely clothed externally with short hair; the _plantæ_ broad; the second joint of the _tarsus_ inserted at the lower angle of the plantæ; _claws_ bifid. ABDOMEN subtriangular, truncated at its base, not longer than the thorax. The MALE differs in having the _antennæ_ as long as the thorax and curved; the _posterior coxæ_ very large and robust, the _trochanters_ small and triangular; the _femora_ large and much swollen in the centre, the posterior _tibiæ_ very large and triangular and convex externally, and the _plantæ_ longer than the rest of the tarsus, and slightly curved beneath longitudinally. NATIVE SPECIES. 1. _labiata_, Panzer, ♂ ♀. 4-4½ lines. (Plate V. fig. 2 ♂ ♀.) GENERAL OBSERVATIONS. The name of this genus comes from _μακρὸς_, _long_, and _ὦψ_, _face_, in allusion to the length of that portion of the head, although this assumed discriminative characteristic is scarcely suitable; this again constitutes another of the many instances wherein it would have been much preferable to have imposed a name without any significancy than one which is not thoroughly applicable. It is, indeed, always dangerous to attach a name to a new genus which has reference to some individual peculiarity, for it may eventually exhibit itself as limited to the one single species or sex to which it was originally applied, as to every other subsequently discovered species in the genus it may be inappropriate.