A spermatophore structured in the bursa copulatrix of the small white Pieris rapae (Lepidoptera, Pieridae) during copulation, and its sugar content

During copulation, the male small white, Pieris rapae, fills a single spermatophore in the bursa copulatrix of the female. The male fills first a white gel and then structures the spermatophore. The sperm was ejaculated last into the reproductive tract of the female, while sugars were observed throughout the copulation. Variation in size and sugar content of spermatophores observed in field-captured monogamous females indicated that sugars were consumed immediately after copulation, and that the spermatophore was gradually eroded. The role of the sugar content is also discussed. INTRODUCTION In butterflies, a spermatophore is passed during copulation. The size of the spermatophore decreases with successive matings (e.g. Pivnik & McNeil, 1987; Royer & McNeil, 1993). A number of studies have shown that males not only contribute sperm but actually make an investment by donating nutrients via the spermatophore (e.g. Thornhill, 1976; Boggs & Gilbert, 1979). Females absorb the nutrients and use them for somatic maintenance or egg production (Boggs & Watt, 1981; Marshall, 1985). The possibility that males may affect the rate of oviposition as well as contributing nutrients for egg production has implications concerning butterfly mating systems. In addition, oviposition is stimulated by the spermatophore (Watanabe, 1988). Egg production requires protein-rich foods, the availability of which may critically constrain a female’s lifetime reproductive success (e.g. Murphy et al., 1983). Most investigations of spermatophore utilization have focused therefore on the use of amino acids by the female (e.g. LaiFook, 1984). Females incorporate amino acids from male ejaculates into their eggs and somatic tissue within 24hr after mating (e.g. Boggs & Gilbert, 1979; Boggs, 1981); receiving more of the non-sperm portion of the spermatophore has been shown to increase female fecundity (Oberhauser, 1989). On the other hand, Pivnik & McNeil (1988) demonstrated that males supplement the sodium requirements of the female via spermatophore transfer. Lai-Fook (1991) showed that labelled phosphorous from the male butterfly, Calpodes ethlius, was deposited in the reproductive tissues of the female. Zinc is also transferred to the female during mating (Engebretson & Mason, 1980). However, there are as yet no reports on sugar content in the spermatophore. Paper submitted 8 November 1994; revised manuscript accepted 3 April 1995.