OR-83b; the auxiliary OR in the ORNs of Drosophila melanogaster :

Each class of ORNs express only one type of Olfactory Receptors together with one additional OR which is expressed in almost all different classes of ORNs; OR-83b. This broadly-expressed OR is evolutionarily conserved and serves as the link between the specific olfactory receptor of an ORN and its localization in the cilium which is necessary for its physiological role. OR-83b binds other ORs and links them to the transport machinery of the cilium to carry the OR up into the cilium (Benton et al., 2006).                                      

The Circadian Rhythm controls the cellular localization of ORs :

Odor-induced electrophysiological responses of the ORNS and the dendritic accumulation of ORs are maximal at midnight (Tanoue et al., 2008). This control is exerted via the rhythmic abundance of GPRK2.