Exploitation of pollen resources by Xylocopa splendidula in the Argentine pampas

The pollen choice by native carpenter bees (Xylocopa splendidula) in the Ar gentine pampas was surveyed by means of the pollen harvest in nests. Sample s were taken in January 1996, 1997 and December 1998. The data obtained wer e compared with data from introduced honey bees, Apis mellifera, in the sam e region (Telleria, 1993). 16 species belonging to 11 families of Angiosper ms are present in the foraging spectrum of X. splendidula. The carpenter be es principally collected pollen from the plants which are isolated or in sm all populations. In contrast forage plants for honey bees are in dense popu lations. Such differences may be attributed to different skills needed to e xploit the resources, and to displacement of native carpenter bees towards less productive environments, by introduced honey bees.