Ground Beetle Identification help

chrisjohnson · #1 (**permalink**) 14-05-2011, 08:47 AM

Hello,
We would appreciate comments on the identification of the beetle illustrated below:

It was caught in a pitfall tap on our compost heap on the north west coast of South Uist, Outer Hebrides on 12 May 2011. It is 5mm long.
We have keyed it to the genus level Trechus, but are less confident about the species level identification. The key takes us to subnotatus - but this is a rare species.
We would appreciate comments and guidance.

thank you

Chris

Jason Green · #2 (**permalink**) 14-05-2011, 11:11 AM

Afternoon Chris,

I can't help with the identification, but is that alcohol you're storing it in (in reference to 2nd image)?

Take care,

Jason

nightshade · #3 (**permalink**) 14-05-2011, 11:40 AM

but is that alcohol you're storing it in (in reference to 2nd image)?
Is there a problem with using alcohol? wrinkling perhaps?

Jason Green · #4 (**permalink**) 14-05-2011, 12:02 PM

Afternoon NS,

I prefer dry-storage of specimens - direct-pinning or micro-staging. When alcohol is used, with a lot of beetles there's the risk of iridescence fading or tiny hairs being dislodged by moving liquid in my view.

We're all different and I'm sure there are advantages I haven't considered

nightshade · #5 (**permalink**) 14-05-2011, 12:28 PM

No criticism intended

I was just curious as I have not pinned or preserved anything much for years (well not really since school) I seemed to remember that preserving in alcohol could cause samples to wrinkle

chrisjohnson · #6 (**permalink**) 14-05-2011, 02:41 PM

Hello Jason
The first image was taken after extracting it from the pitfall trap which contained a 100% salt solution. The second image was taken after washing the beetle in clean water then drying.
Chris

Klaas Reißmann · #7 (**permalink**) 14-05-2011, 02:58 PM

Genus Trechus should be right, even the photos don't show the Trechus-bow on the tip of the elytra. I don't know which Trechus are occuring the outer Hebrides, so I don't know, if ID is possible without dissection of the genitalia. So far, pleasse don't keep ii in alcohol, but make a dry-storage with dissected genitalia.

What do you have pit traps for? Any analysis or what for?

Regards
Klaas

chrisjohnson · #8 (**permalink**) 14-05-2011, 03:59 PM

Hello Klaas

The Outer Hebrides is so under-recorded that nobody knows the full extent of the fauna, so anything is possible. My main interest is moths and in the two years I have lived here, myself and a colleague have added over 40 species to the list.

We are in the process of setting up a Biological Recording Centre here and will be keen to increase our knowledge of many insect groups. I am starting from scratch with coleoptera and this pitfall trap is my first, set to get beetles. I am happy to have a go at dissection but I don't have the literature on 'how to' or to analyse what I have dissected.

Regards, Chris

Klaas Reißmann · #9 (**permalink**) 14-05-2011, 05:02 PM

Hi chris,

if you like or want to, you may send it over to Germany. If not dissected I can do for you. In this case please don't dry it, but keep it smooth and soft, so I have no bigger problems or more work with the dissection.

I suppose that the decision is between Trechus obtusus and Trechus quadristriatus, but I really don't know.

Regards
Klaas

Fauna · #10 (**permalink**) 14-05-2011, 05:23 PM

Quote:

Originally Posted by Klaas Reißmann

Hi chris,

I suppose that the decision is between Trechus obtusus and Trechus quadristriatus, but I really don't know.

Regards
Klaas

I had a quick look at this earlier. There seem to be old records of T. quadritriatus for this area. However the more "up to date" records seem to be for T. obtusus...would be interesting to see what this specimen turns out to be.

Good luck with the Records Centre Chris...

Regards Chris...