Sphaerius is agenus ofbeetles in the familySphaeriusidae, comprising 18 extant species. It is one of the two extant genera in the family, the other beingBezesporum. They are typically found along the edges of streams and rivers, where they feed onalgae; they occur on all continents exceptAntarctica. Three species occur in theUnited States.
The overall form of the beetle is convex, glossy, dark brown or black with some markings possible. The head is prominent, with relatively large eyes set far apart, andcapitate antennae. Total length ranges from 0.5–1.2 mm (0.020–0.047 in).
The beetles occur in a variety of damp environments, including mud, under stones, among plant roots andleaf litter, and in mosses in bogs. They store some air underneath theirelytra.
Females produce a single large egg at a time.
The family used to be known as "Sphaeriidae", but the name was preoccupied by a family of freshwaterclams. The name was inappropriately replaced with "Microsporidae" (by changing the genus name toMicrosporus), but this act has been superseded by a return to the use ofSphaerius and a reformation of the family name as Sphaeriusidae.[2] The position of the family within Coleoptera has also changed a number of times.[3]
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