Gen. PTEROGENIA _Bigot_, MSS.
_Mas et Foem. Platystomati_ affinis. _Corpus_ breve, latum, crassum,
Caput thorace latius, antice planum, genis dilatatis. _Antennæ_ parvæ;
articulus 3^{us} longi-conicus; arista plumosa. _Thorax_ subconvexus;
scutellum magnum. _Abdomen_ thorace brevius et angustius. _Pedes_
breves, validi; tibiæ arcuatæ. _Alæ_ sat parvæ; alulæ maximæ. _Mas._
Genæ angulatæ, valde dilatatæ.
This genus is allied to _Platystoma_ and more especially to
_Trigonosoma_.
_Male and Female._ Body short, broad, thick. Head broader than the
thorax, flat in front; vertex broad; sides of the face or genæ dilated;
epistoma rather prominent. Eyes oblong. Antennæ; small, resting in the
cavity of the broad face; 3rd joint elongate-conical, more than twice
the length of the 2nd; arista plumose. Thorax compact, slightly convex;
scutellum large, conical. Abdomen short, conical, shorter and narrower
than the thorax. Legs short, stout; tibiæ curved, especially the hind
pair. Wings rather small; alulæ very large. _Male._ Sides of the face
more dilated than those of the female, and forming an angle or short
horn on each side.
173. PTEROGENIA SINGULARIS, _Bigot_, MSS. _Mas et Foem._ Nigra, nitens,
capite flavescente-albo fasciis quatuor nigris, antennis pallide
luteis basi nigris, abdominis segmentis flavo marginatis, tarsis albis
apice nigris, alis subcinereis dimidio basali lutescente fasciis
contiguis fuscis, fascia strigisque exterioribus fuscis, halteribus
fulvis.
_Male and Female._ Black, shining. Head yellowish-white, with four
black bands; 1st band on the vertex, broader than the others; 2nd
across the base of the antennæ; 3rd in front of the face; 4th on the
epistoma; antennæ pale luteous, black at the base; hind borders of the
abdominal segments yellow; sides dark tawny towards the base; legs
pubescent; tarsi white, with black tips; wings slightly cinereous;
basal half somewhat luteous, with several partly confluent brown
bands, exterior part with one brown band and with several transverse
brown streaks; veins black, pale luteous exteriorly; discal transverse
vein slightly curved outward, parted by about one-third of its length
from the border, and by more than its length from the præbrachial
transverse; alulæ white; halteres tawny. Length of the body 3 lines; of
the wings 7 lines.