Abstract
Ingestion of a phenyl-benzoyl urea [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea] by Diprion similis (Hartig) interferes with molting. At the highest concentration (1% solution) tested, it prevents ecdysis but does not prevent apolysis. The Cuticle of pharate larvae is thinner than normal but the formation of melanin in the cuticle is not inhibited. At a concentration of.01%, ecdysis is usually completed but many survivors fail to feed following the molt. This failure is associated with the accumulation of a fibrous material in the midgut. Prior to the molt, food consumption as measured by faecal output is not impaired.