This family used to be called Sphaeriidae, but as this is also the name of a group of clams, the beetle family name has been changed to Sphaeriusidae. There is just one species found in Europe, Sphaerius acaroides - see below, and 18 species world wide.
Sphaerius acaroides, above is a tiny (body length 0.7 mm), shiny, hemispherical black or dark brown beetle. It has 11 segmented antennae ending in a club. It is found in sunny, moist, sandy or gravelly places such as ar found along river banks, where it lives in burrows. The larva is aquatic. It is found in central and northern Europe, but is quite rare in the U. K.