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Photo#1772593
Platynus sp. ?  - Laemostenus complanatus

Platynus sp. ? - Laemostenus complanatus
Roseville, 38.7227, -121.2993, Elevation = 50m (164'), Placer County, California, USA
December 17, 2016
Size: 13 mm
The discussion here about Platynus indecentis & decentis relates why I think my specimen leans toward indecentis, and also keys nicely to that genus in Arnett (1) and species in Liebherr (2).

There are no specimens of Platynus indecentis in BG to compare with, and there is no decentis species in the 24 yr old key by Liebherr (2) to separate the two. So I thought it would be interesting to see if this specimen can fill that BG void.

-- Metatarsomere V ventrally setose with 4 on each side pointing down longer than depth of tarsomere.
-- Metafemur with 3-20 setae on dorsoapical surface.
-- Discal setae absent except on edge.
-- Elytral Apical lateral setae.
-- 2 supraorbital setae.
-- 2 pronotal setae (best seen here faintly on right side).
-- Mentum with median tooth.
-- Head constricted behind the eyes.
-- Neck with transverse impression on dorsum of neck.
-- Hind tarsi without dorsal furrow.
-- Simple tarsal claws.

Images of this individual: tag all
Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus Platynus sp. ?  - Laemostenus complanatus

wrong turn
Thank you so much Curt for your comments.

I was looking at many setae that had been broken off, so much of them were without setae. Lesson learned. At least there were not a bunch posted and maybe my detail pictures will help somebody.

 
Definitely useful,
I see this species often mis-identified as various "Pterostichus" or "Platynus" on sites such as iNaturalist, so this detailed series of photos showing the characters will be very useful. I'll direct iNat people to this posting in the future.

Moved
Moved from Ground Beetles.

Laemostenus complanatus
This is an introduced species, and they are pretty similar-looking to Platynus.
See couplet 2 in the key to Platynini genera in American Beetles (p. 57) - the dorsally setose metatarsi separate this genus from the others.

P. indecentis looks a lot like decentis, so it would have a much narrower pronotum than this beetle, and a shinier dorsum. The locality of this beetle is a red flag that it isn't indecentis, also. That species is adapted to live only in cold sphagnum bogs in northeastern N. America.

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