Bee flies and bluets:Bombylius(Diptera: Bombyliidae) flower-constant on the distylous species,Hedyotis caerulea(Rubiaceae), and the manner of foraging

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Abstract
Bombylius major and B. pygmaeus visited bluets almost exclusively at several eastern North America sites even though other flowers were abundant, and they were also the most persistent visitors to the flowers. Foragers often visited most of the flowers in a bluets patch in just two days and picked up pollen on their proboscides. Based on the sequences of visits to distylous bluets morphs (pins and thrums), and the time spent by a fly at either morph, Bombylius foraged randomly between morphs. This behaviour was probably a result of both morphs being equally abundant and evenly distributed, and an inability of the flies to distinguish between morphs. It is suggested that pollen handling by the flies has a major effect on Hedyotis pollen flow.