Evening R, and welcome to WAB
I remember being fascinated by these at school/home when I was a kid. I infact posted about this one recently and other members have had similar stories of it from their childhood. A nostalgic insect!
Follow this link - any matches?
Rove Beetles - Subfamily Tachyporinae Photo Gallery by Tom Murray at pbase.com
They are known as
Rove Beetles, from the sub-family 'Tachyporinae', taxonomically.
Hope this helps!
Take care,
Jason 