Lipid droplets in the pheromone glands of bombycids: Effects of larval diet on their size and pheromone titer

•Lipid droplets (LDs) in pheromone glands (PGs) store fatty acid pheromone precursors.•Fatty acid content in the larval diet affected LD size and number in Bombyx mori.•The sex pheromone titer was affected by dietary fatty acid levels to a lesser degree.•LDs were found in the PG of Trilocha varians, the closest non-congener of B. mori.•LDs in PGs play an important role in the regulation of sex pheromone titer.