The hermaphrodite aquatic snail Biomphalaria glabrata (Say) facultatively self-fertilizes. As an inter-mediate-host for the human parasitic helminth Schistosoma, it represents an important experimental model. Experiments were undertaken to investigate whether factors other than copulation might have implications for the fertilization process and subsequent fecundity. There were five experiments: (i) without pairing; (ii) pairing for 24 h; (iii) pairing for a single act of copulation only; (iv) pairing with a surgically castrated male acting partner for 24 h; (v) snail pairs kept in the same water for 10 days, but without physical contact. Data on numbers of egg-masses, eggs, developed eggs, and hatchability were analysed by t and chi-squared tests. The results suggest that fecundity can be influenced by currently unidentified aspects of behaviour that might include chemical or other cues.