Nests of Osmia nigriventris. 17, 18) Nest 16 X-rayed (left) and dissected (right). 19, 20) Nest 18 X-rayed (left) and dissected (right). 21) Old nest 8 with short blind burrow on the right. 22–23) Old nests 2 and 6 later used by Euodynerus quadrifasciatus as nesting site. 24) Old nest 1 with brood cells of Osmia leaiana in the upper half and remnants of the old nest of O. nigriventris in the lower half.