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At least this one appears to key out to Olcella using Sabrosky's chloropid key in the Manual of the Nearctic Diptera. My understanding is that the Nearctic species are in need of revision so I haven't tried to take the ID further. However, confirmation/correction of the ID would be much appreciated
Thanks in advance
Steve







dorsal view of right wing illuminated 2 different ways to show the unpigmented venation


focus stack taken at higher magnification/resolution than the 1st dorsal stack

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Chloropidae, Oscinellinae: Olcella Enderlein, 1911. Altogether 28 valid species of this genus are known, 11 in the Nearctic, 16 in the Neotropic and one in the Australasian Realm. Many species are undescribed. Several species are known as kleptoparasites or commensales, participating in the prey of raptorious arthropods which feed on their preorally digested victims. In the Old World Trachysiphonella, Conioscinella and Oscinimorpha are comparable genera with species sucking this liquid food, partly being also flower visitors and pollinators and possessing elongate probosces. Arid and salt-influenced biotopes of dry areas and semideserts are preferred biotopes. But bogs in Canada house species, too. Flies were reared from Bromus grass and grasshopper eggs. On the enlarged images [in dorsal view] two pairs of elongated prescutellar acrostichal setae are visible between the dorsocentral bristles. One pair is normal for the genus Olcella, but two pairs are already mentioned for two undescribed species by Wheeler (2010: 1142, couplet 12) in Vol. 2 of the „Manual of Central American Diptera“. Olcella spp. formerly were partly described into the genera Botanobia, Conioscinella, Madiza, Neoolcanabathes, Oscinella, Oscinis, and Siphonella. If you twice enlarge the image of the hyaline wing you will detect the five sensilla on vein R4+5 which seem to have never been considered in phylogenetic studies on Acalyptratae.

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Thanks Dr. von Tschirnhaus. Much appreciated!

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I think there are the sensilla Dr. von Tschirnhaus is referring to.

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Dr. von Tschirnhaus asked me to post some similar images of the whole wing that were processed to accent the sensilla so here goes
unfortunately, the processing also brings out every speck of dirt on the wing

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same image annotated

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Nice picture. Similar and possibly homologous structures in the fungus-feeding Cecidomyiidae are used in modern keys to genera and tribes.

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Thanks John, I'll add it to the BugGuide post. These weakly pigmented wings are hard to photograph with my setup. I thought an approximation of darkfield would work but it actually hides these structures