Two nonassociative components of the proboscis extension reflex in the blow fly, Phormia regina, which may affect measures of conditioning and of the central excitatory state.

With the use of controls not included in previous studies, evidence is presented for the existence of water-induced central excitatory state (w-CES) from analyses of pure-breeding high- and low-CES lines in the blow fly, Phormia regina. The CES lines differed in base-level responsiveness to distilled water (and to saline) as well as in response levels for w-CES and for sucrose-induced CES, which suggests the existence of genetic correlates for several components of the proboscis extension reflex. Recognition of several nonassociative components complicates the interpretation of individual scores in earlier studies of proboscis extension conditioning and of the central excitatory state.