Castilleja miniata (Scrophulariaceae), a host plant for the plume moth Amblyptilia (Platyptilia) pica (Walsingham) was found to contain the dipiperidine alkaloids (-) ammodendrine and (-)-N'-methylammodendrine, and the quinolizidine alkaloids (+)- 13-ahydroxylupanine, and (+)-tetrahydrorhombifoline. incomplete structural evidence was also obtained for an unknown tetrahydrorhombifoline derivative and an artifact pyridine monoterpene alkaloid, probably cantleyine. Flowers of Penstemon whippleanus (Scrophulariaceae), another host plant for the plume moth, were found to contain the pyridine monoterpene alkaloid (+)-boschniakine and two incompletely characterized members of this class, probably 4-noractinidine and carbomethoxypedicularine or their isomers. Alkaloid or alkaloid metabolites (as yet unidentified) were present in the plume moths and larva that inhabit each plant species.