Excavator: Ground. Charles Ferton (1893) was the first to describe nests H. annulata annulata, under the name of Osmia crenulata. He states: "The insect nests in flat clay-rich terrain. [The brood cells are] at the bottom of a vertical gallery, dug to a depth of six or seven centimetres. The gallery closes with an oval [brood] cell oval. The provision is violet coloured, and almost a homogeneous liquid (...) The walls of the cell, probably coated with a mucilage, are smooth". Ferton believed the nests contained a single brood cell, but susequent observation has shown them to have 1-4 cells at the end of the main burrow or of side burrows.
Nesting material: The brood cells are excavated from the ground, smoothed and hardened on the inside, but not entirely built of mud. Cell partitions and nest plug are made of mud. The nest burrow sometimes circumvents obstacles such as small stones. The nest entrance is hardened and little narrowed, often hidden near a plant base or under a stone. (Ferton, 1892; Mavromoustakis, 1957; G. Le Goff, personal observation)