This one was a new one on me, and it was a wonder I saw it in the first place. It is only about 3 to 4mm (0.2in) long. It is one of the spider beetles for it has quite long legs. It has distinctive white patches on its wing casings. In the image below it is in a defensive posture with its long antennae tucked in at its sides.
Apparently this little beetle does the cleaning up, and it feeds on decaying insects. It has been found inside bees nests where it feeds on detritus, and possibly pollen stores for the bee larvae, which may then cause problems for the developing bees.
Rear garden, Staffordshire, England. June 2017.