A sex pheromone secreting gland in the terrestrial snail, Euhadra peliomphala

The head-wart found in the snail, Euhadra peliomphala, consists of a number of elevated dermal tubercles covered by a particularly thick epithelium. The head-wart and its epithelial cells attain full size by rapid growth at the time of sexual maturation. When two snails meet in the breeding season, their head-warts become conspicuously protuded. After touching the partner's head-wart with large tentacles, each becomes excited, protrudes its penial mass, and finally copulates. Protrusion of the head-wart and copulation are observed at the same time. By the use of head-wart extract similar sexual behavior can be experimentally induced in snails. From these observations, it may be concluded that it is the epithelial surface of the head-wart of a sexually mature snail which releases the substance that promotes sexual behavior. This physiologically active substance is considered to be a kind of sex pheromone. This pheromone does not appear to serve as a sexual attractant but serves rather to sexually excite another snail thus evoking a courtship response following their initial encounter.