Red & Black Beetles

Red & Black Beetles

Observation - Red & Black Beetles - Global. Description: I photographed these beetles today next to Manzanares Castle near Madrid, Spain. They were joined at the tails and I watched them moving for 10 minutes with no separation and one of them dragging the other. What are they? Was their joined tails a fre

I photographed these beetles today next to Manzanares Castle near Madrid, Spain. They were joined at the tails and I watched them moving for 10 minutes with no separation and one of them dragging the other.

What are they?
Was their joined tails a freak of nature or were they mating?

Many thanks.