Abstract
Bio-assay showed that the pheromone of attractive female Trypodendron lineatum (Oliv.) must be produced in the posterior part of the ileum. Histological studies revealed a layer of secretory cells in the rear part of the ileum and the rectal valve which occur only in feeding adults. The attractive material is produced only when bark and wood particles are present at the site of pheromone production, and the actual production is initiated probably by activity of a female hormone or enzyme.