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Please note this is an informal description done for fun.

Female. 4 mm. Head short and round, slightly swollen, with integument reddish yellow on the parafrontals and becoming yellow on the parafacials and below, ocellar tubercle black, triangle undifferentiated, pruinescence nearly absent, thinly whitish on the gena and occiput. Occiput entirely black setulose, postocular row black setose. Front at vertex about 0.36 times head width, widening towards antennae. Parafrontals mostly bare, with several short black setulae restricted to the posterior half. Frontal vitta yellow, at middle about as wide as either parafrontal, widening slightly anteriorly. Postocellar setae present, parallel. Inner and outer vertical setae present, inner slightly longer, pair convergent and cruciate, setae meeting near the tips. Ocellar setae present, proclinate, situated between posterior and anterior ocelli. Upper reclinate setae present in 1 pair. Lower proclinate setae present in 8–9 pairs situated closely to frontal rows, extending down to nearly whole row. Frontal setae present in about 11 pairs, all inclinate, none descending below antennal bases, but lowest 2 oblique arrangement from main frontal row. Parafacials bare, wide, at narrowest about half the width of the face. Face concave, not visible in profile, without a median carina separating antennae, lower portion narrowed. Vibrissa barely differentiated as more robust setae, crossed, angle situated distinctly above lower facial margin. Facial ridge setose on lower third, supravibrissal setae of 4–5 setae. Antennae about a third as long as the height of the face, but situated on the upper fourth of the face, leaving about a third of the face below the antennae, bases narrowly separated by distance less than width of scape. Scape and pedicel yellowish. First flagellomere uniformly bright yellowish orange, rounded, 1.7–1.8 times as long as pedicel. Arista light brown, with tiny whitish area in the middle, cylindrical, nearly bare, as long as antennae or longer, first aristomere minute, second barely longer than wide, third thickened only on basal fifth. Gena with dark setulae, wide, about a third head height and half eye height, with groove extensive, ending nearly at facial ridge, forming a very large genal dilation. Eyes bare. Proboscis not elongated. Palpi present, well-developed, yellow, somewhat short and strongly expanded apically.
Scutum reddish, becoming yellowish on the humeri and the scutellum. Pleura reddish, mostly bare with few sparse, black, short setulae. Anterior thoracic spiracle yellow, small. Posterior thoracic spiracle reddish. Chaetotaxy: acrostichals 2+2-4 (2 posterior pairs distinctly developed, 2 anterior pairs weak); dorsocentrals 2+3; intrapostalar setae weak or absent; intraalars 1+2 (anterior about as far from suture as first dorsocentral); posthumeral 1 or 1+1; presutural 1; humeral 2, mostly bare posteriorly; notopleura 2, bare of setulae; supralar 2, anterior shorter than or about as long as dorsocentrals; postalar 2; prosternum bare; proepisternum bare, lower portion with 1 short seta, directed upwards; proepimeron with 2 setae, directed upwards; anepisternum with a posterior row of 6 setae, with 1 anterodorsal seta, 2 short setulae below it; katepisternal 2, with anterocoxal row of 4 setae curved posteriorly; katepimeron bare; anepimeron with a cluster of 4-5 short setae; meron with row of 6-7 setae; infrasquamal hairs on the postalar wall absent; scutellum with 6 pairs of setae total: a basal pair, 2 lateral pairs about the same size, curved, a longer convergent and cruciate subapical pair, a very short, convergent and cruciate apical pair, and a short discal pair. Disc of scutellum mostly bare, clothed with dark setulae except for a broadly bare basomedial area, without erect, subapical setae.
Legs moderately stout, entirely yellowish except for claws and pulvilli, covered in black vestiture, fore tarsi slightly darkened apically. Chaetotaxy: Cx1 with medial area bare, only setose at the margins; T1 with row of numerous ad (10 or more), 2 p; Cx2 with row of 8 or so anterior setae curved posteriorly; F2 with 2 a/av, 2 ad, 2 pv; T2 with 1 av, 2–3 ad, 2 pd; Cx3 bare posteriorly; F3 with 1 basal av, row of 5 d, 2 pv; T3 with 2-4 av, row of 10 ad, widely separated, of various sizes, 3 outstanding, row of 7 pd, widely separated, of various sizes, 2 outstanding. Tarsi with tarsomeres normal. Claws and pulvilli shorter than fifth tarsomere. Claws black, pulvilli whitish.
Wings pictured, with contrasting yellowish, brownish, and hyaline area. One crossband present. Picture as a yellowish costal area from base to middle of cell R1, reaching down to crossvein r-m, conspicuously a brown spot on the crossvein, and back to cover cell Br. Picture also brownish yellow on almost the entire basal portion of the wing and as a single disjunct apical crossband that crosses crossvein dm-cu and recurves to terminate near the middle of cell dm. Tegula and basicosta yellow. Costal spine distinct, in length about 1.5 times the width of the costa. Costal arc between vein Sc and R1 three or more times as long as costal spine. Vein R1 bare. Vein R4+5 basally and dorsally with 4 setae in a row less than a third of the distance to crossvein r-m, ventrally even shorter. Vein M sinuous, ending in wing margin, away from the end of vein R4+5 by distance shorter than length of crossvein r-m. Bend of M sinuous, angle roundedly perpendicular to obtuse, without a spur vein or fold in the membrane as a continuation, much closer to wing margin than crossvein dm-cu, latter convex or bowed outward in the middle, the latter joining M about half the distance from crossvein r-m to bend of M. Vein CuA1 with distal section very short, ending before wing margin, about 0.14 times the length of the preceding section. Vein A1 not reaching wing margin. Calypters uniformly yellow, with yellow pubescence throughout and fringe. Halteres uniformly yellow.
Abdominal dorsum and venter subshining reddish yellow with black spots and bands. Tergite 1+2 with only a marginal, black, dash-like spot on the median fifth. Tergite 3 with black posterior band about a ninth of the tergite's length thick, continuing to the sides, not reaching venter, and expanding into a median black triangle that extends up to less than half of the tergal length, triangle about as wide as median spot on tergite 1+2. Tergite 4 with black posterior band about a fifth of the tergite's length thick, continuing to the sides, only narrowly reaching venter, and expanding into a median black triangle that extends up to half of the tergal length, triangle about as wide as base of median triangle on tergite 3, triangle more truncate than that of tergite 3. Tergite 5 trifasciate, with 3 long black spots or stripes equally spaced. Tergite 1+2 without setae, only recumbent black setulae, with median depression narrow, restricted to anterior half to two thirds of segment. Tergite 3 without discal setae, with 1 pair of median marginal setae, 3 pairs of short lateral setae. Tergite 4 without discal setae, with several marginal setae extending to sides, median pair slightly displaced forward. Tergite 5 truncate, round apically, with transverse discal row of 13 setae extending to ventral margins of tergite. All sternites hidden, ventral margins of tergites overlapping. Ovipositor not modified into a sickle.

I have been wanting to find these flies for a while. Contrary to what the key on the Manual of Nearctic Diptera suggests, vein M does not meet vein R4+5 well before the wing margin in this specimen and probably the whole genus. This specimen keys to couplet 319. The vibrissa are very poorly differentiated but the postgenal margin forms a distinct genal dilation. The katepisternum has 2 setae and 2 postsutural supra-alar seta similar to genus Eutrixa. Otherwise, this species keys variously to Trigonospila and Euhalidaya. The mid tibia has only an anteroventral seta on the ventral surface, not directly ventral, and interestingly, the frons has a row of proclinate orbital setae extending to nearly the end of the frontal row of setae.
No accessible key to species to Oestrophasia has been made since Wulp in 1890. Oestrophasia sabroskyi was diagnosed by Kovarik & Reitz in 2005. They write females in the subgenus Oestrophasia lack the pointed ovipositor of subgenus Cenosoma. The only species in our area in subgenus Oestrophasia are O. calva and O. clausa. Both sexes of O. clausa have vein R4+5 almost entirely setose to crossvein r-m, and the abdomen is more extensively dark, with dark median vitta that continues past the tergites. O clausa has also not been collected in Florida. Oestrophasia calva has probably not been traditionally described since its original description in 1902 by Coquillett. As a result, there little to expect and disagree with from the description. However, Coquillett's description mentions the vertex being twice as wide as either eye in the female, which is ridiculously wide. This should be an error as most tachinid flies don't have such widely separated vertices. In addition, the "first segment" of the abdomen (tergite 1+2) is written as having marginal setae, which are lacking in this specimen. Both sexes of O. sabroskyi are described as also lacking setae on tergite 1+2. Looking at BugGuide photos, the development of these setae might vary intraspecifically, but are never well-developed.
A systematic analysis of the tribe Dufouriini by de Santis & Nihei was made in 2022 which included O. calva. The species was not fully redescribed but an extensive character matrix was created. This specimen matches nearly all characters, except for the yellow postnotum (this may be sexually dimorphic) and only 2 anterodorsal setae on the female mid femur instead of the 3 suggested. BugGuide images of this species also show less than 3 setae present on this surface of the mid femora.

Location: Europe > Portugal > Algarve

Date Photo Taken: June 12, 2011

Determination: Dr. Hans-Peter Tschorsnig - "Probably a male of Chetogena acuminata Rondani, 1859"