Factors affecting cocoon orientation in Osmia lignaria propinqua Cresson (Hymenoptera: Megachilidae)

Laboratory and field studies on Osmia lignaria propinqua Cresson were designed to determine: how cocoon orientation is established by the species; and, if misdirected cocoons affect survivability of adults emerging from nests having cells in linear series. Bore diameter, size of larvae, position of fecal particles in cell, position of provision loaf, and gravity were found to influence orientation of the cocoons produced by this species. These may act separately or have a cumulative effect on orientation. Particular factors will over-ride others when directional influences on cocoon orientation are in conflict. Details on cocoon construction and types of cocoons spun by this species are described. Data accumulated demonstrate that survivability of adults during emergence was not affected by direction of cocoon orientation within nests.