Structural, Behavioral, and Physiological Adaptations of Bees (Apoidea) for Collecting Pollen

Abstract

Bees, like their wasp relatives, forage for and transport food to a nest as provisions for their offspring. Unlike female Sphecoidea which transport arthropods one at a time as prey, bees transport pollen requiring specialized scopal (brush) or corbicular (fringed plate) structures to transport the dustlike material externally. Scopae often exhibit further modifications in density and amount of plumosity in relation to the size and ornamentation of the pollen grains they transport. Bees also differ from sphecid wasps by possessing branched body hairs that are relatively densely packed. These hairs, the electrostatic surface potential, and specialized hair groups for extraction of hidden pollen are important in the acquisition of pollen from flowers. Structures for grooming (brushes, combs, and scrapers) and grooming behavior patterns are modified to permit manipulation and packing of pollen in the specialized transport structures. The addition of nectar, so that pollen is packed moist, is a behavior that permits the carrying of pollen of a great variety of sizes and ornamentations in relatively simplified scopae or in corbiculae. The addition of oils to the diet of some bees has resulted in a modified type of scopal structure that has a wooly area basally and stiff guard hairs extending distally and that can transport a mixture of oil and pollen. Special hairs on the fore and mid basitarsi and teeth of hind tibial spurs are modified as oil scraper and manipulation structures. The use of corbiculae in Apidae to transport nesting materials and the hind tibiae in male orchid bees (Euglossini: Apidae) for transporting aromatic compounds involves behavior patterns similar to those for pollen transport in grooming, manipulating, and packing the materials. Other behavioral and physiological adaptations important in the location and acquisition of pollen by bees include individual constancy, oligolecty, seasonal synchrony, preimaginal conditioning, daily synchrony, buzz pollination, and other responses to specific modes of pollen presentation. Most of the behavioral patterns involve learning. They may be modified by extrinsic factors, and they may modify intrinsic structural and physiological characters.