The Oulema problem

The Oulema genus are Chrysomelid beetles. They are small but rather beautiful. These are the kind of beetle that you find and think, "Oh that'll be easy to identify...." Er, wrong! Yes, easy to get to genus but beyond that, dissection is required (Bezdek and Baselga 2015). Worse, with males once dissected out the aedaegus has to be opened up.

Images of the same Oulema sp beetle, but which species? (I didn't identify this individual, it walked/flew.)

Back on 11th June 2024 I caught an individual of this genus, in our kitchen on the window, a source of quite a few interesting records. I researched the genus, asked for some help which was kindly provided, dissected the specimen and came out at the identification Oulema duftschmidi which was iRecorded, duly verified and is now a dot on the NBN, there are few Scottish records.

 

Oulema duftschmidi

 

So that was June last year and here we are in April and at the beginning of the month a few of these turned up - on the dog, in the outside dog water, inside the kitchen window etc. My expectation was that these would all be Oulema duftsschmidi like the one from last year, wrong! These are all Oulema melanopus. I am now wondering about last year's animal. Something I have learned recently is that the dissection I carried out last year was inadequate for identification, it is necessary to dissect the aedaegus itself which I did not do. I'm now left wondering about the identification of that individual, but it was of course two months later so perhaps there are some seasonal differences in these species, their phenology may differ. More later.

 

Male aedaegus dissected out to show the flagellum, proving O. melanopus.
 

 

Female genitalia I'm not sure if this dissection is good enough to prove O. melanopus. I may have broken the important bits off.

Images of the genitalia are available in the paper cited above, but the male flagellum of O. duftschmidi is fine and thin, quite unlike the image above. The differences in the female genitalia are more subtle - "the junction of ductus spermathecae and bursa copulatrix (short and abruptly connected to finger-like process of bursa copulatrix in O. melanopus, long and gradually extended in O. duftschmidi (cf. Figs 26, 27)." ((Bezdek and Baselga 2015).

 

 

 

 

Another beetle issue has been with keys and Amara. The Amara are those bright and shiny Carabid beetles that you may observe scuttling about in the grass on sunny days. There are quite a few UK species and they pose and ID challenge. The main problem is that all the keys rely initially on two quite tricky criteria; these are the presence or absence of a pore at the base of the scutellar stria and/or whether the apical spur of the front tibia is single or split into three points. It might be expected that these criteria are clear, unfortunately they are not. With the pore I was left wondering whether the small pit I could see (or imagined I could see) was the pore present or not. And with the apical spur, until you have gained a fair bit of experience it is a tricky thing to make out unless you can orientate the leg in exactly the correct position. And even then some interpretation of what you are looking at is required.

 

Amara lunicollis

Amara lunicollis front leg, inner side

Pretty sure I have this one correctly, Mark Telfer's key is the easiest to use, but the most useful images are on the German beetle site here - https://www.coleonet.de/coleo/texte/amara.htm

 

 All tricky.