Microsania, Zetterstedt, 1837

Grimaldi, David A., 2018, Basal Cyclorrhapha In Amber From The Cretaceous And Tertiary (Insecta: Diptera), And Their Relationships: Brachycera In Cretaceous Amber Part Ix David A. Grimaldi, Bulletin of the American Museum of Natural History 2018 (423), pp. 1-97 : 1-97

Microsania sp.

Figures 5 , 31

SUMMARY: Complete female in Baltic amber; with typical array of Microsania characters (see generic diagnosis above). Additional details include the following: M, Cu veins with minute gap between apices and wing margin; bm cell and vein CuA2 appear incomplete (the former possibly an artifact of preservation); 2 pairs fronto-orbital setae, anterior pair inclinate, posterior pair latero-proclinate; strong pair of interfrontals present; pair of long, fine presutural setae (probably dorsocentrals) present; prescutellum appears present.

DESCRIPTION: Head: Eyes bare, red; dichoptic. Frons with faint median furrow on anterior half; pair of interfrontals present, well developed, proclinate; 2 pairs of fronto-orbitals, anterior pair inclinate, slightly more posterior pair latero- proclinate. Pair of ocellar setae present, long, divergent, smaller pair posteriad. Lateroclinate pair of outer verticals present; inclinate pair of inner verticals, plus other setae on vertex; postoccipital setae well developed.

Clypeus (face) bulging; vibrissa, genal setae absent. Proboscis relatively broad but short.

Antenna: Scape and pedicel short, ringlike; pedicel with setulae; arista terminal, basal flagellomere ovoid, with sensory/glandular pit and seta on dorsal surface; basal aristomere minute, short; apical aristomere long, not particularly fine, micropubescent.

Thorax: Short, deep in lateral view, rounded and slightly arched. Acrostichals uniserial, ~ 7 in row; dorsocentrals in pair of rows, ~7–8 setae each row, anteriormost pair long, fine, ~3× length of posterior dcs, ~ 5 scattered setae lateral to dcs. 1 large supraalar seta; 1 large postalar; 6 scattered notopleural setae. Anepisternum, katepisternum, anepimeron bare. Scutellum short, broad; with two pairs setae, apical pair cruciate; prescutellum present. Wing: Relatively elongate, length 2.3× width; darkened between Sc and R 1, with darkened area extending past apex of R 1; membrane entirely covered with well-developed microtrichia. Vein C with spinules, longer on portion from apex of R 1 to base; C terminates at apex of R 4+5, portion between terminus and apex of R 1 hardly sclerotized. Sc about half the length of R 1; R 4+5 terminates at apex of wing. Cell rm absent; cell bm open apically (bmcu appears incomplete), crossvein dm-cu (cell dm) absent. M 1 basally incomplete; M 2 complete; between apices of M and Cu veins and wing margin with a minute gap. CuA 2 short, apically incomplete(?), cell cup small, possibly open; A 1 apically evanescent; anal lobe well developed, alula with long flattened setae. Legs: Coxa laterally attached to thorax; length of femur ≊ tibia on all legs; all podomeres setulose. Largest setae on legs stout, spine like; 2 on dorsal surface mesotibia (at 0.3× length of tibia, plus preapically); 1 dorsally on metatibia and metabasitarsomere, both preapical. Setae and setulae on all tibiae and tarsi in longitudinal rows. Mesotibia and tarsus with 2 ventral, seamlike rows of stout, short setulae. Metatarso- meres 1 and 2 with transverse rows setulae. Claws and pulvilli well developed. Metabasitarsomere barely expanded in lateral view. Abdomen: Abdomen relatively short, stout, distinctly shorter than wings; 8 well-developed tergites, 6 well-developed sternites visible. Tergites with short, scattered setae (no macrosetae), sparser on sternites; sternites nearly equal in size to tergites on same segment. Pleural membrane wrinkled and exposed between lateral margins of abdominal sclerites. Cerci small, 1-segmented, suboval.

SPECIMEN EXAMINED: Female, AMNH Ba-502-14, in Eocene Baltic amber. Specimen is complete and well preserved (the eyes have even retained a reddish color), but portions of the cuticle are obscured by a milky coating.

COMMENTS: I chose not to name this fossil because I could find no diagnostic characters to separate it from extant species, one reason being it is a female.

Figures

FIG. 5. Microsania sp. (Platypezidae), female, AMNH Ba502-14, in Eocene Baltic amber. A. Right lateral habitus. B. Frontal view of head.

FIG. 31. Microsania sp. (Platypezidae), female, AMNH Ba502-14, in Eocene Baltic amber. A. Wing. B. Thorax, lateral view. C. Head, frontal. D. Antenna. E. Thorax, dorsal.