They have a short, furrowed abdominal stem, two submarginal cells in the forewing and a well developed head, especially behind the compound eyes.

Based on the course of the submarginal veins the genus is divided into three species groups, which some authors also regard as subgenera.

Some species also use abandoned feeding tunnels in the wood or build their nests in plant galls.

Short side passages are often first filled with bore dust and only later developed into cells.

In many species, the larvae do not pupate in a complete cocoon, but in a cap over the head, which can be a thin membrane that merges into the wall of the brood cell.