Plant chemistry, insect adaptations to plant chemistry, and host plant utilization patterns

Examined the importance of furanocoumarin chemistry in determining distribution patterns of the parsnip webworm Depressaria pastinacella in a population of its host plant, wild parsnip Pastinaca sativa. Parsnip webworms feed almost exclusively on wild parsnip, a species that produces furanocoumarins, compounds that are toxic or deterrent to many insects. When larvae are fed plant tissues with below-average total furanocoumarin concentrations, consumption rate is the most important larval characteristic determining growth rate, but when larvae are fed plant tissues with above-average concentrations of furanocoumarins, the capacity to metabolize furanocoumarins is also important. Plant chemistry, relative to larval ability to tolerate plant chemicals, can to a large extent explain the distribution of this insect within a population of its host plant. -from Authors