Taken from Lindgren Funnel Trap set out for a few days & nights, 9 mi. south of Colfax, on Pine Lake Dr., 666 m elevation (2,185 ft), 39.0651, -120.9440.

Add CA to the Distribution map for Platystethus.

Important characteristics in Arnett (1), some not in pictures.
-- Hypomeron very narrow as seen in the ventral close-up (head oriented to the left) of the large procoxal cavity with the lateral arch of the cavity close to thorax edge at the top of the image.
-- Abdominal tergites showing the lack of curved basolateral ridges (Arnett (1). Taken from a sister specimen from the same location 60 days later because wings completely covered dorsum) A specimen with basolateral ridges can be seen here.
-- Mesocoxae slightly separated (couldn't get a picture) by very slender ridge.
-- Tarsi hard to count, but I believe 3-3-3.

Hope I'm right on the genus and will get a species id help. I couldn't find a good key to species.