Ground beetle: Agonum or Chlaenius

NickU · #1 (**permalink**) 07-05-2010, 03:01 PM

Can anyone help to identify this ground beetle with a green/bronze sheen at least to genus. Maybe Agonum sp. or Chlaenius sp?

17.4.10 Wiltshire

Nick Upton - naturalist and photographer

Rossco · #2 (**permalink**) 07-05-2010, 03:36 PM

Nick, it's neither. It's an Amara of some sort. This genus has a fair few species, many of which are very similar.

NickU · #3 (**permalink**) 07-05-2010, 06:32 PM

Many thanks Rossco... the shape looks good for Amara now i've checked some pics and I can see there is an "inordinate" number of lookalikes, so Amara sp. will do!
Nick

Jason Green · #4 (**permalink**) 07-05-2010, 07:39 PM

Evening Nick,

I agree with Ross, an Amara sp. - can you remember how long it was? It's male, too.

Take care,

Jason

Fauna · #5 (**permalink**) 07-05-2010, 08:45 PM

I've got a migraine so forgive me if i'm out here...i'm thinking its Poecilus versicolor or P.cupreus

oxycera · #6 (**permalink**) 07-05-2010, 08:51 PM

Yes, I must admit I had Pterosticus in mind.

Paul mabbott · #7 (**permalink**) 08-05-2010, 09:13 AM

Not Amara, I think, and not Chlaenius. Not the best view - did you get any other pictures? Top on, perhaps? As someone else asked, what size was it? What habitat was it in?

NickU · #8 (**permalink**) 08-05-2010, 10:26 AM

Many thanks to you all for your comments and suggestions.

The beetle was sunning itself on a weed covered (nettles, dead nettles, dock etc) earth mound at the margin of a cow pasture. From memory, it was around 2 cms long. I got a few other shots including this top shot, but the focus is poorer as it was shifting quite fast.

Later the same day (17.4.10) I was by a river bank about 2 miles away and a very similar (to my inexpert eyes), but possibly slightly smaller carabid was on a little island of vegetation about a foot from the shore. When it saw me, it deliberately entered the water and swam confidently for shore, and I got these photos. I realise this may be a different, more river-associated species, but add the photos of it swimming/ on the shore for interest / and would like to get an ID for this one as well if possible if it is different! These must be early season species as this was one of the first sunny, warmer days of this year.

Many thanks, Nick

Paul mabbott · #9 (**permalink**) 08-05-2010, 10:55 AM

Size alone (although I think you exaggerate a tad

) makes it a Poecilus (formerly Pterostichus). The pale proximal antennal segments make it P. cupreus or P. versicolor - to decide between the two you should be able to see fine pits on the head of P. cupreus! However P. cupreus is usually somewhat larger and is also by far the most common - so seems the most likely.

Fascinating observation of one in water. Many ground beetles (particularly Loricera pilicornis but many species of Bembidion, Leistus & Agonum) are amphibious and will retreat into water when threatened. I've not heard of/seen Poecilus doing this before so an interesting sight.

NickU · #10 (**permalink**) 08-05-2010, 12:26 PM

Hi Paul, Ok many thanks for the great feedback. Here is a crop of another shot where the focus was best on the head, and at least in my high res original I can see fine dimpled pits catching the light, so I think that does make it Poecilius cupreus. Yes, size may well have been smaller, certainly smaller than a Violet ground beetle, but bigger than most other garden carabids I see. I found a good carabid site about the Ground beetles of Ireland
with good pics and info and it does say P. cupreus is typical of damp meadows and lake shores and likes warm places, so the sunning behaviour I saw and locations fit. As for the swimming, will look out for this again whenever I'm near the river again. It seemed to be up some vegetation when I first saw it, again sunning or foraging, but swam for shore when I saw it. I know Bembidion aeneum well from a former period of my life studying saltmarsh inverts..
Nick

Irish beetle site is: Poecilus cupreus :: Ground Beetles of Ireland ::