93 days to go to National Insect Week
The Biological Records Centre (BRC), established in 1964, is a national focus in the UK for terrestrial and freshwater species recording. BRC works closely with the voluntary recording community, principally through support of national recording schemes and societies.
There are lots of contenders here – possibly the pretty red and blue rove beetle Paederus – very, very tiny amounts of its poison have been used to cure chronic ulceration in people. Ladybirds are pretty poisonous (and pretty) and can bleed foul-tasting poisonous brightly coloured blood from their knees.