The ecology of solitary bees

Bees play an important and necessary role in the pollination of agricultural crops grown for fruit and seed and of forage and browse plants important in range management for production of both livestock and game animals. Nearly 20,000 different kinds of bees are now known, some, like the imported honey bee, the bumble bees, and the stingless bees of the tropics, are social and live together in colonies subject to manipulation and movement from place to place. However, by far the majority of bees are solitary, living in burrows in the ground, in wood, or in plant stems, where they store pollen and nectar as food for their young. Many of these take pollen only from certain kinds of plants and are very efficient pollinators of these. Others, like the honey bee, visit a wide variety of pollen plants, both native and introduced. Although management procedures have been developed for certain crops in certain areas which permit the effective use of honey bees for increased production through better pollination, these are not universally applicable to our agriculture as a whole. For certain crops, both cultivated and wild, supplemental pollination is necessary. The development of management procedures which will permit increased utilization of native solitary bees and perhaps lead to the importation of foreign species native to the areas in which our agricultural crops originated, requires a detailed knowledge of the ecology, or environmental relationships, of these bees. This article is intended to review as briefly as possible, the current status of our knowledge of the subject and to indicate published papers in which various aspects may be pursued further. Prominence has been given to publications of the last fifteen years and to those which are most comprehensive and include references to earlier literature. Factors which appear to have had an influence in the economy, evolution, and survival of solitary bees have been especially emphasized.