Differential Visitation of Catasetum Orchid Male and Female Flowers

Abstract

In June-July 1979, in Santa Rosa National Park, Costa Rica, a Catasetum maculatum orchid produced two successive five-flowered female inflorescences and attracted at least 407 male Eulaema polychroma o¥er 59 flower days; only two of these bees carried pollinaria and they pollinated three of the 10 flowers (Janzen 1981). In June 1980, the same plant produced a six-flowered female inflorescence and attracted about the same number of male E. polychroma per day as in 1979, but none carried pollinaria. Likewise in June 1980, a heavily shaded Catasetum maculatum orchid produced a five-flowered male inflorescence about 150 m north of the other orchid. The flowers began producing odors about 0700. By one-half hour later, four of the flowers had their pollinaria removed by the first four bees (E. polychroma) to arrive, and by 15 minutes after that the last flower lost its pollinaria to the fifth E. polychroma. Each bee spent 30 to 90 seconds at the flower. Flowers stopped odor production as soon as the poUinaria were remO¥ed, as evidenced by the fact that I could no longer smell them individually, and incoming bees made no mistake as to entering a flower that had lost its pollinaria. These five flowers were the only flowers made by this plant in 1980 (in 1979 it made two bud -bearing inflorescences, both 0 f which were eaten by herbivores).