ID : Two Beetle Species

[Andrew C]

Afternoon,

I have two beetle species I would like to ask for identification assistance on.

The first image shows a larger black beetle found on higher moor ground outside Tiverton in Mid-Devon. I have had a few goes at this one and can't seem to get a confident conclusion going through the Nebria key. I get close to Nebria rufescens but it does not feel right. Is this a Nebria species or a different family altogether?

The second smaller one was found in the compost bin in the garden and I suspect it to be Brachinus crepitans but wanted to ask for confirmation or otherwise first.

Regards,
Andrew.

[Jason Green]

Afternoon Andrew,

The second is either Oulema melanopus or O. rufocyanea, and can'd be done without examination of the male or female genitalia.

B. crepitans has an orange head and the insect with a generally flatter habitus.

Take care,

Jason

[Andrew C]

Originally Posted by Jason Green

Afternoon Andrew,

The second is either Oulema melanopus or O. rufocyanea, and can'd be done without examination of the male or female genitalia.

B. crepitans has an orange head and the insect with a generally flatter habitus.

Take care,

Jason

Evening Jason,

Thanks. I would struggle to even dissect the specimen as it was rather small! I took delivery of a microscope this morning but I deemed it too poorly built so I have returned it. I shall go and see if I can read up on Oulema species now.

Regards,
Andrew.

[Paul mabbott]

The black one is a Pterostichus. If it's around 1cm and from a damp/wet area, I would think it is Pt nigrita (or Pt. rhaeticus, you need to examine the undersides to differentiate these). PS: Apparently Pt. rhaeticus is more abundant at higher altitude. I have to confess that I have spent very little time trying to separate these two.

[Andrew C]

Originally Posted by Paul mabbott

The black one is a Pterostichus. If it's around 1cm and from a damp/wet area, I would think it is Pt nigrita (or Pt. rhaeticus, you need to examine the undersides to differentiate these). PS: Apparently Pt. rhaeticus is more abundant at higher altitude. I have to confess that I have spent very little time trying to separate these two.

Thanks ever so much Paul. It is 10.5mm from front to rear not including the antennae and was found on moorland at an altitude of roughly 240m above sea level according to the relevant OS Map. The habitat is damp boggy moorland covered in Purple Moor Grass. I still have the specimen if you are able to tell what feature I should look for.

Regards,
Andrew.

[Andrew C]

Hello again,

Using 'The Carabidae' by Martin L. Luff, I went through the key for Pterostichus and it took me to P. longicollis but that was with me not entirely sure the antennae colour was reddish brown as opposed to black. It depended how the light shone on it.

Regards,
Andrew.

[Paul mabbott]

Originally Posted by Andrew C

Thanks ever so much Paul. It is 10.5mm from front to rear not including the antennae and was found on moorland at an altitude of roughly 240m above sea level according to the relevant OS Map. The habitat is damp boggy moorland covered in Purple Moor Grass. I still have the specimen if you are able to tell what feature I should look for.

Regards,
Andrew.

You're a braver man than I am. First you'll need to examine the genitalia, even then it's not 100% certain. In males you need to compare sizes/shapes of the parameres. Females are easier but, again, comparative: it's the relative sizes/shapes of the eighth sternite (Beetles, Coleoptera | www.bumblebee.org) - narrower in Pt. rhaeticus with a very acute apical angle.

You'll perhaps see why I abandoned attampts to identify these - you really need to compare several individuals from different habitats.

[Andrew C]

Originally Posted by Paul mabbott

You're a braver man than I am. First you'll need to examine the genitalia, even then it's not 100% certain. In males you need to compare sizes/shapes of the parameres. Females are easier but, again, comparative: it's the relative sizes/shapes of the eighth sternite (Beetles, Coleoptera | www.bumblebee.org) - narrower in Pt. rhaeticus with a very acute apical angle.

You'll perhaps see why I abandoned attampts to identify these - you really need to compare several individuals from different habitats.

That casts a different light on it now and makes me reach for the white flag!

Thanks for your advice anyway, Paul. It was much appreciated.

[Jason Green]

Originally Posted by Andrew C

That casts a different light on it now and makes me reach for the white flag!

...or the point where you begin getting serious!

[Paul mabbott]

Pt. longicollis has a distinctively shaped forebody and it is also distinctly brown (that's not particularly helpful because most Pterostichus are brown when recently emerged), not jet black like Pt. niger.
Try Luff using black antennomeres? Mmmmm

Originally Posted by Andrew C

Using 'The Carabidae' by Martin L. Luff, I went through the key for Pterostichus and it took me to P. longicollis but that was with me not entirely sure the antennae colour was reddish brown as opposed to black. It depended how the light shone on it.

Regards,
Andrew.