Abstract Varying degrees of ovarian development were induced in overwintered Dendroctonus pseudotsugae Hopk., put on (1) host logs, (2) bark chips, or (3) moist glass paper. In 96 hours the ovaries of beetles on logs reached maturation, those on bark chips showed only slight growth, and the third group failed to show any development.Farnesyl methyl ether induced significant ovarian development in beetles kept on bark chips or glass paper. It appears that production or release of gonadotrophic hormone is withheld in insects kept outside their natural gallery environment. Sensory input associated with gallery excavation may initiate ovary development by stimulating endocrine activity.