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

Genus Microsania Zetterstedt

DIAGNOSIS: Male holoptic, female dichoptic; female frons with well-developed orbitals and

pair of interfrontals (latter sometimes present or visible in male); postoculars long, occiput setose. Face protruding (clypeus bulging) in female; basal flagellomere oval to subcircular; arista micropubescent. Acrostichals present, uniserial; dorsocentrals in two uniserial rows. Thorax short, deep; scutum in lateral view arched. Metabasitarsomere and tarsomere 2 (sometimes 3) laterally flattened, expanded; tarsomere 1 is longest of metatarsomeres; legs without dark, bifid scales. Wing with Sc, R 1 sclerotized, short, latter slightly over 0.5× length of wing. Pterostigma large, between entire R 1 and Sc and extends apically past R 1. Base of M 1 incomplete; wing with membrane entirely microtrichose. Cell cup small; crossvein dm-cu absent. Alula with flattened setae; male abdomen with longer setae, terminalia curled under abdomen.

COMMENTS: This is a global genus of some 23 named extant species: 5 Australia + New Zealand, 4 Asia, 2 Pacific Islands ( Vanuatu, Fiji), 2 Africa, 8 Palearctic, and 2 New World. The North American specimens are in serious need of revision (there are more than just two species), and I have also seen new species from Mexico, Peru, and Chile. Species are rather uniform externally (males are best separated using genitalia), and females of some species cannot be distinguished with certainty (e.g., Chandler, 2001).

The female specimen in Baltic amber described below is the first fossil of the genus, and it is remarkably similar to modern species. A detailed comparison of the females of world species is needed to determine whether there are features of this fossil that allow diagnosing it as a species. In the meantime, I am deferring formally naming it, just noting the impressive morphological stasis of Microsania from the Eocene to the present. Surprisingly, this is also the only definitive platypezid known in Baltic amber (though an undescribed opetiid is known), despite the centuries of collecting and studying Baltic amber insects in Europe. Interestingly, the amber piece resided for more than a century in an old collection of darkened, crazed Baltic amber insect inclusions at the AMNH, which was purchased from Ward’s Scien- tific Establishment in Rochester, New York, in the early 1900s. It was originally labelled as an empidid. The deteriorated surfaces were removed, better revealing the fly. The fly is partially coated with a milky exudate, typical of the preservation of insects in Baltic amber.