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Hi colleagues, is my identification of this tiny fly as Drosophilidae correct? Can you help me with any further identification to subfamily/ genus level?
Sample location is a Polynesian atoll, yet this fly was collected around garden facilities (papaya, banana, various vegetables,...), so it might as well be an introduced species.

Thanks for any help and input
Best
Seb

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I would say it is the sufamily Steganinae. If I am right, the dorsal aspect of mesootum should show a pair of enlarged presutural acrostichals.

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Also count the number of rows of acrostichals and see whether the basal scutellar bristles are divergent or convergent. If it is a common species, not recently introduced, it should be in Malloch's 1934 key: http://hbs.bishop...14-179.pdf.

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Dear John, Dear Jan,
thanks for the input and literature recommendations. I identified this species as Drosophila nasuta, based on Malloch's 1934 key. Under greater magnification, both the short bristles on the forefemur and the single black bristle on the mid tarsus are well visible.
Thanks!

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According to the catalog Drosophila nasuta is no longer recognized from the region. Check D. sulfurigaster (Duda, 1923, originally described as genus Spinulophila) which is another member of the same species group. More specifically, D. sulfurigaster bilimbata Bezzi, 1928 is the subspecies spread across the islands.

http://hbs.bishop...lidae.html

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John, thanks for the hint. According to Ramage 2017, the Drosophila common throughout the Soceity Islands is D. coffeina. Unfortunately, I could not find any keys that include this species or have clear illustrations, but the description of this species by Schiner 1868 read like a good match.

The (dipteran) fauna is poorly monitored here, especially on the more remote islands further away from Tahiti. I have already more than 10 new species records for French Polynesia and several more morphospecies that I still need to identify, including at least 3 morphospecies of Phoridae, one Conopidae, Hybotidae and Scatopsidae - all dipteran families that were so far unknown to occur in French Polynesia. Therefore, the literature on geographical distribution is not necessarily a good criteria to support morphological examinations.