Plum wrote:
Today I found a bright green beetle-type insect I'd never seen
before. It was about half an inch long, chunky but rather angular,
with a black spot on its rear end. Does anybody recognise it from
this description?


' It was about half an inch long, chunky but rather angular,'
......... sounds like a shield bug.
Strictly, not a beetle but a true 'bug'.
Many varieties, which go through several maturity changes (instars),
all of which can be differently marked. So an identification might be
difficult.
Look up 'Shield bug' on Google Images and see if anything looks
similar.
...... or, there is a green shield bug on
http://www.abcHood.com/exnats

If you found it on a particular plant, that might help.

--
ned