NESTING AND FORAGING BEHAVIOR OF ANDRENA (CALLANDRENA) RUDBECKIAE ROBERTSON (HYMENOPTERA, APOIDEA, ANDRENIDAE) IN TEXAS

The foraging and nesting biology of Andrena rudbeckiae was studied ove r a four year period in central Texas. The few-celled, single-occupant nests are gregarious and structurally simple with the fully lined cel ls occurring at soil depths of 94 to 118 cm. Females commonly make 6-8 pollen trips per day with pollen trips averaging 33.5 min. Male cells are estimated to require one day to provision while females require t wo. Pollen collection is restricted to the coneflower genera Rudbeckia and Ratibida (Asteraceae) with time spent per head increasing with th e number of staminate phase florets per head. Males patrol the emergen ce site, nonflowering shrubs near the nest site, as well as pollen hos ts. Bees overwinter both as adults and defecated larvae in their natal cells, an unusual pattern in Andrena. Nomada (Phelonomada) belfragei was regularly present at the nest site and was recovered from nest cel ls of A. rudbeckiae. This is the first host report for any Phelonomada .