I often see these brightly coloured beetles in the summer on sunny days resting on bushes or flying on flower heads to hunt for small insects, adult beetles can be seen between May and July,
There are other Cardinal beetles in the United Kingdom, Pyrochroa Coccinea is similar but with a black head. Red in colour to warn predators that it toxic to eat so it is undisturbed during the day.
It’s the flat larvae that have always interested me that live under the barks of fallen deciduous trees as a young boy I collected some of these larvae from a local forest and reared them in rotten logs in tanks just to find out what they would turn into. The yellowish larvae are long and flat so they can easily move around under barks of trees. They also have two sharp prongs at the back, which is probably used to help move around or as a defence because I have held them between fingers and they can direct the prongs upwards which are strong and sharp. The larvae are carnivorous feeding on insects such as beetle grubs hiding in rotten wood.