THE NESTING-BEHAVIOR OF THE MASON BEE OSMIA-CORNUTA (LATR) WITH SPECIAL REFERENCE TO ITS POLLINATING POTENTIAL (HYMENOPTERA, MEGACHILIDAE)

The nesting behaviour of Osmia cornuta was studied in managed populations released in almond orchards. A correlation between the dry weight of a provision and the number of pollen grains in the provision was established. Male and female provisions contain a mean of 4 634 304 and 8 046 425 almond pollen grains, respectively. A correlation between the dry weight of a provision and the number of foraging trips was also established. The mean number of foraging trips necessary to complete a provision was 16.76 for male provisions and 26.79 for female provisions. During an almond blooming period, each O cornuta female potentially visits from 9 500 to 23 600 almond flowers. Given the pollinating efficiency of O cornuta on almond, 3 females per tree are considered sufficient to maximize pollination in an almond orchard.