Structure of Celonites jousseaumei nest N on 19th of April: a exterior view b brood cells opened in longitudinal direction c cell content removed. (N1–N3 = brood cell numbers; aw = apical cell wall; bw = basal cell wall; e = egg; hs = hollow space below pollen loaf; l = larva; nr = nest rim; ns = nest seal; p = pollen loaf; pa = papilla on surface of pollen loaf; s = bare stone surface; measurements and cell content summarized in Table 2).