Age structure of male Euglossa imperialis (Hymenoptera: Apidae: Euglossini) at nectar and chemical sources in Panama

Abstract

Bees in the tribe Euglossini (Apidae) form an important component of the pollinator fauna in lowland, Neotropical forests (Dressler 1982, Janzen 1971, Williams 1982). The community structure and seasonality of male euglossine bees are relatively well known because they can be attracted to chemical baits (Ackerman 1983a, Dodson et al. 1969, Janzen et al. 1982, Pearson & Dressler 1985). The male bees are important pollinators of many orchids (Dressler 1968, Williams 1982) from which they collect fragrant chemicals; these chemicals are also collected from other plants and decaying vegetation (Ackerman 1983b, Dressler 1982). Male bees are known to store collected chemicals in hind tibial organs (Dressler 1982) and, it is presumed, use these chemicals to synthesize sex pheromones (Williams & Whitten 1983). Mating occurs in territories to which males attract female bees (Dodson 1966, Kimsey 1980). Recently, Schemske & Lande (1984) found that captive male Euglossa imperialis show elevated levels of territorial behaviour when provided with cineole, a fragrant chemical that readily attracts male bees, compared to control bees maintained without a chemical source. Although the exact function of the fragrant chemicals is still unknown, these were the first results that clearly implicated fragrance collection in male reproductive behaviour. Schemske & Lande (1984) noted that the male E. imperialis provided with a daily source of cineole actively collected the fragrance only on the first day of the 11 day experiment. One potential explanation for this observation is that males require only one collection of chemical fragrance before establishing territories. Thus, only the youngest bees in the population would be expected