4 DIPTERA. 
ACAULONA, gen. nov.* 
Body rather bare. Head large, notably broader than the thorax; eyes bare, with the inner orbits almost 
perpendicular ; front (in both sexes?) broad ; frontal bristles short and weak; cheeks narrow, with a row 
of short hairs near the eyes and a pair of bristles placed at some distance above the oral margin ; this 
latter a little prominent. Antenne half as long as the face ; second joint somewhat elongated ; third 
joint elliptical, nearly double as long as the second ; arista bare. Proboscis not longer than the head ; 
palpi small, thickened towards the end. Thorax (seen from above) quadrate, with distinct transverse 
suture; scutellum semicircular. Abdomen convex, ovate, with five visible segments; segments 1-4 of 
equal length; the apical segment much smaller, with two short appendages beneath (male genital 
organs ?). Legs rather short, with a few dispersed, weak bristles. Tegule large. Wings longer than 
the abdomen, the costa and hind border parallel, the apex rounded ; apical cell ending at the wing’s apex, 
closed but not petiolated; curvature of the fourth vein rounded ; posterior cross-vein somewhat curved, 
beyond the middle of the apical cell. | 
On account of the distinctly visible five abdominal segments, this genus must be 
referred to the ‘ Phasine,’ and not to the ‘Gymnosomine ; in the latter the abdomen 
shows but four segments. Acaulonais nearly allied to Xysta, but is distinguished from 
it by the broad front and the almost total absence of pilosity. In its general facies it 
has some affinity with Cistogaster (of the Gymnosomine group); but differs from that 
genus by the number of abdominal segments, and by the non-petiolated apical cell. | 
I include in this genus a single species from Mexico. 
1. Acaulona costata, sp.n.(%). (Tab. III. figg.1; 1a, head; 16, abdominal 
appendages. ) | 
Head yellowish-white; frontal band, antenne, thorax for the greater part, scutellum, and legs (except the 
base of the femora), black; abdomen fulvous, with large, triangular, blackish dorsal spots ; costal half of 
the wings fuscous. 
Length 5 millim. 
Front as broad as the eyes; its lateral borders and the whole of the face and cheeks yellowish-white ; frontal 
band very broad, velvety-black ; palpi pale rufous. Thoracic dorsum black, opaque, before the trans- 
verse suture whitish, with three broad, black, longitudinal bands; pleure grey; scutellum black, 
Abdomen slightly glossy, fulvous, with a large, triangular, brownish-black spot on each segment, that on : 
the fourth segment extended over almost the whole surface; last segment entirely rufous, its appendages . 
black. Legs black; coxe and base of the femora rufous; hind tibiee outwardly convex; claws and 
pulvilli very small. Tegule yellowish. Wings grey, on the anterior half fuscous; this dark colour 
limited by the fourth vein up to the small cross-vein, and for the rest, though not so well-defined, by the 
third vein. 
Hab. Mexico, Orizaba (H. H. Smith & F. D. Godman), Medellin near Vera Cruz 
(H. H. Smith). 
A single specimen from each locality. These agree perfectly with one another, and 
are apparently both males. 
Group GYMNOSOMIN A. 
No species of this group are contained in the collection before me, nor are there any 
recorded from Central America. Two genera, Gymnosoma and Cistogaster, are found 
in the United States. 
* G (absque), kavdds (petiolus). 
