Palatability of monoterpenoid compositional types of Satureja douglasii to a generalist molluscan herbivore,Ariolimax dolichophallus

The differential palatability of monoterpenoid compositional types of Satureja douglasii to a native slug herbivore, Ariolimax dolichophallus, was determined. Types containing a high proportion of bicyclic monoterpenoids (camphene, camphor) were more palatable than those containing high proportions of p-menthane monoterpenoids (isomenthone, pulegone or carvone). In the case of individual monoterpenoids characteristic of these types, camphor proved to be most palatable and pulegone the least; carvone and isomenthone were intermediate. Differential herbivory on the compositional types was observed under field conditions. It is suggested that differential herbivory could have been important in determining the patterns of monoterpenoid variation and their distribution in S. douglasii.