e. No frontal lunule above the base of the antennæ; both R_4 and R_5 often present; third segment of the antenna often with a terminal bristle. ASILIDÆ, MYDAIDÆ, APIOCERIDÆ, THEREVIDÆ, SCENOPINIDÆ, BOMBYLIIDÆ, EMPIDIDÆ, DOLICHOPODIDÆ, LONCHOPTERIDÆ. ee. A frontal lunule above the base of the antennæ; third segment of the antenna always simple, i.e., not ringed, usually with a dorsal arista; R_4 and R_5 coalesced into a simple vein. f. A spurious vein or fold between the radius and the media, rarely absent; the cell R_{4+5} closed at the apex by vein M_1; few or no bristles on the body, none on the head; flies frequently with yellow markings. ERISTALIS (fig. 163i), HELOPHILUS, and many other genera. SYRPHIDÆ ff. No spurious vein present. g. Body without bristles; proboscis elongate and slender, often folding; front of both male and female broad. CONOPIDÆ gg. Bristles almost always present on head, thorax, abdomen and legs. h. Arista terminal; hind metatarsus enlarged, sometimes ornamented, hind tarsus more or less flattened beneath PLATYPEZIDÆ hh. Flies having a different combination of characters. i. Head large, eyes occupying nearly the entire head; cell R_{4+5} narrowed in the margin; small flies. PIPUNCULIDÆ ii. Head and eyes not unusually large. j. Squamæ (tegulæ, or calyptræ, or alulæ) not large, often quite small, the lower one lacking, or at most barely projecting from below the upper one (antisquama); front of both male and female broad, the eyes therefore widely separated; posthumeral and intraalar macrochæta not simultaneously present; thorax usually without a complete transverse suture; postalar callus usually absent; the connectiva adjoining the ventral sclerites always visible; hypopleural macrochætæ absent; last section of R_{4+5} and M_{1+2} with but few exceptions nearly parallel; subcostal vein often wanting or vestigial or closely approximated to R_1; the latter often short, basal cells small, the posterior ones often indistinct or wanting; vibrissæ present or absent. ACALYPTRATE MUSCOIDEA