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Water Scavenger Beetle - Cercyon laminatus

Water Scavenger Beetle - Cercyon laminatus
Groton, Middlesex County, Massachusetts, USA
July 23, 2011
Size: 3.7mm
Attracted to lights.

I now feel fairly confident about the ID. Smetana will have the final say, hopefully.

ID confirmed by A. Smetana
this species has been previously collected in Quebec though the records were unpublished. This find however represents the first for the continental USA.

give him my best regards and utmost admiration for his work.

suspect Cercyon (Paracycreon) laminatus Sharp,
...a variable, rather large (2.8-3.9), very common e. Asian sp. that looks very much like this and has made its way to Europe (and then some) >50 yrs ago and is now a staple around the Baltic & Mediterranean (also Hawaii)(1)(2) (habitus); the key(1) separates it early (from the rest ~25 spp. of e. Siberian fauna) based on almost keel-like, pointed mesosternal process. I have not seen specimens with elytra uniformly dark like here, but the amount of dark varies liberally, and this variant wouldn't surprise me at all --compare this. See also Fikáček (2009) (Chilean record)

Confirms my suspicions
that this is mostly likely a nonnative species- I didn't have a reference for the Palearctic species, so it got me stumped when I tried running it through the North American keys. The elytra are actually not uniformly dark- the apices have a large, distinct pale spot that extends along part of the posterior lateral margins. So this may actually turn out to be a much more significant find than just a state record!

Cercyon cf. luniger
This one keys out to Cercyon luniger in Smetana (1978)- the extremely narrow mesosternum and flattened body profile suggest that it is this species. The problems are (1) this is an uncommon beach specialist along the Pacific coast and (2) the stria seem abit too deeply impressed for this species (described as 'shallowly' impressed to obscure) I'm not 100% convinced. It's definitely not C. fimbriatus as the mesosternum in that species is somewhat wider. I tried to find a reference specimen to compare it to at the collection out here but we apparently don't have this species's not commonly collected. I've posted a picture of the metasternal/mesosternal region to accompany this image.
Not sure where to take it from here...perhaps you may want to notify Don about this finding? He will most likely want this as it is potentially a new state record.


Interesting one
I have not been able to get a conclusive ID on this one yet...
this resembles the coastal beach-dwelling species on the Pacific coast(flat body shape, relatively large size, narrow mesosternum)..I considered C. litoralis but body size is off (max size for C. litoralis is around 3 mm). I'll have to get this under a better microscope to examine the details better.

Sounds like a good one
The location for this one is about 40 miles inland from the coast.

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