Dung beetles, Chafers and Stags
We have a decent number of species in the UK but only these species routinely occur at light traps.
Instead of reinventing the wheel I have (with permission) posted the resources freely available on the web.
For Geotrupes get the following shots:
Dorsal view underside of abdominal segment hairs Jaw edge if possible
One of the larger species of beetle to find in a trap, affectionately known as May or Doodle Bugs. They are much larger than the smaller and daintier
Serica brunnea. There are 2 native species, both attracted to light.
If you happen to be trapped in the North, look out for the rarer Melolontha hippocastani, and make sure you record it if you do!
These are the largest group of dung beetles in the UK, and have recently had some name changes, so be aware when searching the web.
For example Aphodius rufipes is now called Acrossus rufipes.
For all things Aphodius, British Scarabs have got you covered.
Acrossus rufipes is by far the most common dung beetle attracted to light, often in large numbers. Its large size and semicircular clypeus (front of head) makes it instantly recognisable after a bit of practice.
Stag beetles: Lucanidae
Most people will be able to spot a stag beetle a mile away. We have 2 large species that are attracted to light in the UK, The impressive Lucanus cervus with the male's mahogany antlers and the smaller (but equally exciting) lesser stag beetle, Dorcus parallelipipedus
Elytra (wingcases) always dark brown and glossy
Males with large antler like mandibles
There are some great pictures of both males and females HERE
Elytra (wingcase) always black, and not glossy
Both males and females with smaller mandibles
Male with more transverse head than female