ID : Beetle species

[Andrew C]

Good evening,

A few rotten logs at Knightshayes NT just outside Tiverton in Devon, UK had some beetle species. I have tentatively identified them as Pterostichus madidus due to their chestnut coloured legs but the rear angles of the pronotum are sharp as opposed to blunt.

Is anyone able to advise me as to what species this is from the attached photographs?

Regards,
Andrew.

[Fauna]

Hi Andrew

I believe this is a Nebria sp, either N. brevicolis or N. salina.

N. brevicolis will have hairs on the upper surface of the hind tarsi, N. salina will not show any at all. I will have a closer look later, as the width of the pronotum edge can also help in sperating the two...but for the moment i'm leaning toward N. brevicolis as this is the commoner of the two.

Edit...Pm also sent.

Regards Chris...

[Andrew C]

Originally Posted by Fauna

Hi Andrew

I believe this is a Nebria sp, either N. brevicolis or N. salina.

N. brevicolis will have hairs on the upper surface of the hind tarsi, N. salina will not show any at all. I will have a closer look later, as the width of the pronotum edge can also help in sperating the two...but for the moment i'm leaning toward N. brevicolis as this is the commoner of the two.

Edit...Pm also sent.

Regards Chris...

Evening Chris,

Thanks for chipping in with a correction. I have had another look at the specimen's hind tarsi and I am undecided. Careful examination with a 10x triplet hand lens under a good light shows it to have no hairs on the upper surface of the tarsi. It is easier to see hairs than to decide if hairs are absent and the edge of the pronotum appears to be relatively wide but I have never seen either species knowingly.

With a lack of a microscope, this one may possibly have to remain unidentified unless we go by habitat?

Another thing I forgot to mention is that when handled, the specimen gives off a strange smell.

Regards,
Andrew.

[Fauna]

The hairs can usually be seen using an hand lens. Make sure the legs are dry, and thouroughly check both legs. The hairs can be hard to spot as they will be sparse and pale. I've had to check a few times on certain individuals. If you are certain that there are no hairs present (not even one), then it will be N. salina.

I can't make out the beading properly from the photo, so i'm unable to go any further from that feature. This feature is best learnt from having both species side by side...it will be very slight in difference.

Many Carabids give of a strange smell, i've noticed this on a number of the larger types. Carabus seem to give off the worst smell.

Regards Chris...

[Andrew C]

Originally Posted by Fauna

The hairs can usually be seen using an hand lens. Make sure the legs are dry, and thouroughly check both legs. The hairs can be hard to spot as they will be sparse and pale. I've had to check a few times on certain individuals. If you are certain that there are no hairs present (not even one), then it will be N. salina.

I can't make out the beading properly from the photo, so i'm unable to go any further from that feature. This feature is best learnt from having both species side by side...it will be very slight in difference.

Many Carabids give of a strange smell, i've noticed this on a number of the larger types. Carabus seem to give off the worst smell.

Regards Chris...

I gave it another go using a brighter and whiter LED light. Even trying to silhouette any hairs present proves the absence of hairs on the upper surface. So N. salina it is then. Thanks.

Regards,
Andrew.

[Paul mabbott]

I wouldn't like to hazard a guess from the pictures but it does look quite chunky - Nebria salina is slightly more delicate than N. brevicollis. Habitat is a good indicator: N. brevicollis tends t be abundant on loams and most woodland soils while N. salina tends to be found on sandier soils, especially heath.
I don't find the hind tarsal hairs as easy to see as Chris (my eyesight!) and I would always use a microscope preferably with back lighting. One reason linked to this is that in older (second year) specimens the hairs may be worn away and it is necessary to check for pits (setal pores) where the hairs used to be; in truth I've not found this very often!

[Fauna]

Originally Posted by Paul mabbott

I don't find the hind tarsal hairs as easy to see as Chris (my eyesight!) and I would always use a microscope preferably with back lighting. One reason linked to this is that in older (second year) specimens the hairs may be worn away and it is necessary to check for pits (setal pores) where the hairs used to be; in truth I've not found this very often!

Yes, thanks for bringing this to light Paul, i agree

I think it was fairly presumptuous of me to direct the idetification of these by just using an hand lens. I should have worded...you can occasionally see the hairs on N. brevicollis by using an hand lens if they are showing well. But it can be more difficult to be sure that there are no hairs...so in this case a microscope is indeed a must.


Regards Chris...

[Klaas Reißmann]

Hi everybody,

the tarsal hairs of Nebria brevicollis is somewhat for an experienced coleopterologist. They easily brake so you can't see them and have to look for the left over porosities that can not easily be seen.

It is more easy to take a look at the first limb of the jaw feelers. In Nebria salina it is very dark brown or black, not as light brown as the others. In Nebria brevicollis it is the same colour as the others.

So the one in this picture must be Nebria brevicollis. Another good hint is the kind of ground. Nebria salina lives on very sandy or stony grounds, here in western Germany mostly in heath. The ones found on fields, grasing land and others, where the soil is normally more or less loamy, are Nebria brevicollis.

Regards
Klaas

Edit: Very useful for comparisons is the tool on kerbtier.de

http://www.kerbtier.de/cgi-bin/enXCompare.cgi

You can compare up to six species. Just tipe in the genus name. Klick on the first beetle and than klick on field "A" and the picture of this beetle will emerge in big. Klick on the next beetle, klick on the field "B" and the picture of the second beetle will emerge in big and so on.

[Fauna]

Originally Posted by Klaas Reißmann

Hi everybody,It is more easy to take a look at the first limb of the jaw feelers. In Nebria salina it is very dark brown or black, not as light brown as the others. In Nebria brevicollis it is the same colour as the others..

Cheers for this Klaas, you learn something new everyday.

I have just checked over some of mine, it fits the bill with what i've got. I wonder why this is not in the keys i have (or it probably is somewhere and i've overlooked this feature)?

I have noticed on a few confirmed N. salina that the tarsi can look like it has these porosities, which just adds more confusion (i've got one here that shows it on the right hind tarsi). I've noticed in my area that N. salina is more choosey with its habitat, while N. brevicolis seems to be more casual. I do find both together on the Colliery spoil tips in my area.

Regards Chris...

[Andrew C]

Originally Posted by Klaas Reißmann

Hi everybody,

the tarsal hairs of Nebria brevicollis is somewhat for an experienced coleopterologist. They easily brake so you can't see them and have to look for the left over porosities that can not easily be seen.

It is more easy to take a look at the first limb of the jaw feelers. In Nebria salina it is very dark brown or black, not as light brown as the others. In Nebria brevicollis it is the same colour as the others.

So the one in this picture must be Nebria brevicollis. Another good hint is the kind of ground. Nebria salina lives on very sandy or stony grounds, here in western Germany mostly in heath. The ones found on fields, grasing land and others, where the soil is normally more or less loamy, are Nebria brevicollis.

Regards
Klaas

Edit: Very useful for comparisons is the tool on kerbtier.de

Compare beetle photos - kerbtier.de

You can compare up to six species. Just tipe in the genus name. Klick on the first beetle and than klick on field "A" and the picture of this beetle will emerge in big. Klick on the next beetle, klick on the field "B" and the picture of the second beetle will emerge in big and so on.

Morning Klaas,

Thanks for the alternative key method in determining the correct identity of this specimen. The specimen was found in rotting logs in a small stand of trees and laurels which could be considered a micro-woodland. Thanks also for the link to the beetle comparision website.

Regards,
Andrew.