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Photo#1427824
Threvids - Ammonaios confusus - male - female

Threvids - Ammonaios confusus - Male Female
Bishop area, Inyo County, California, USA
August 8, 2017
Size: ~10mm
Found on rocky hillside with riparian habitat and river nearby. Same pair as .

Images of this individual: tag all
Threvids - Ammonaios confusus - male - female Threvids - Ammonaios confusus - male - female

Moved
Moved from Stiletto Flies.

Moved
Moved from Stiletto Flies.

 
Great! Thanks, Martin
...for verifying the ID. Neat creatures :-)

Moved
Moved from Flies.

Great photos: They definitely clarify diagnostic characters & ID
After carefully scrutinizing the full-size versions of your two photos here, I have no doubt these are definitely Therevidae (which we strongly suspected before).

Moreover, diagnostic characters visible in your photos allowed me to fairly confidently navigate the MND(1) key to genera for Therevidae, leading fairly clearly to genus Ammonaios (or, less likely, perhaps Arenigena) via the couplet sequence:

1. No clear pairs of dorsocentral setae (instead the entire scutum is covered with fairly dense, long, yellowish-white pile, some of which forms three continuous, longitudinal, vittae — smothering the position where any putative dorsocentral setae/bristles might exist. Besides, this is clearly not Apsilocephala, which is the alternative choice.)..........2
2. Mid coxa with pile on posterior surface (clear on female at right of your image above)..........3
3. Prosternum with pile in and around central depression (again, visible in the female above)..........4
4. Lower frons tomentose; head not strongly protruding anteriorly; compound eyes of male not separated between frons & vertex...........5
5. Lateral portion of face, or at least its upper part, with pile (I'm thinking this is the right choice here, if not these end up at Arenigena)...........14
14. Frons in both sexes with dense appressed pile of whitish scaly hairs. Macrosetae of mesonotum pale. A circular blackish area usually present in and around each anterior tentorial pit..........Ammonaios
Regarding the last character mentioned in key break 14, the blackish area around the tentorial pit (near the bases of the antennae) appears more "linear" than "circular" to me (in both your shot of the female and mine of the male)...but I'm thinking that's partly due to foreshortening from the perspective of our photos (i.e. the obliquely downward viewing angles).

If this is indeed Ammonaios, then studying:

Hauser, Martin & Michael E. Irwin (2003). The Nearctic Genus Ammonaios Irwin and Lyneborg 1981 (Diptera: Therevidae). Ann. Entomol. Soc. Am. 96(6): 738-765. (Full Text)
...my best guess would be A. confusus, due to the dark costal cell & stigma; and what appears to be a black, shiny, hairless area directly around the tentorial pits (near base of antennae). That species has records not far from our location here (e.g. at Fish Slough).

If the pair turns out to be Arenigena instead, my best guess would be A. albiseta (which also has a record from the Fish Slough area).

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