Nest‐building behaviour was studied inXylocopa violacea, with particular attention to that exhibited in the construction of each cell, from the formation of the pollen paste to the construction of the diaphragm. Seven inside characteristics of 28 nests excavated in driedArundo donaxcanes were determined. The cell length ranged from 14 to 20 mm. The diaphragms separating the cells were 2 mm thick in the middle, and 4–5 mm at the edge. In 37 additional nests, only data on some characteristics were taken: (a) colour of the pollen paste; (b) cane internode used for nesting.X. violaceais univoltine and solitary, and as in all the otherXylocopaspecies, female average fecundity is very low (7.43 eggs per nest), despite considerable maternal investment. UnivoltineXylocopaspecies are less fertile than multivoltineXylocopaspecies because of the one to three sup plementary generations per year.