|Bosch gras, Jordi|
Submitted to: Journal of Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/9/1999
Publication Date: N/A
Citation: Interpretive Summary: This study explores the possibility to move actively nesting populations of the solitary bee Osmia cornuta. Nesting shelters with known numbers of nesting females were moved at night, and the number of females that continued to nest was counted on the first, second, third and seventh night after each move. Bees moved short distances (3 m) do not appear disoriented dafter the move, and continue to nest at the relocated shelter. Bees moved several hundred m or several Km appear disoriented after the move, and many of them do not continue to nest at the relocated shelter. Some females return to their original nesting site and hover at the exact place from where the shelter was removed.The number of females that do not continue to nest at the relocated shelters increases with moving distance. The addition of artificial visual landmarks (plastic banner with color patterns) to the nesting shelter does not affect the female's tendency to disperse after distant moves. Females imprisoned in their nest and released at different distances from their nesting site are able to relocate their shelter from as far as 1.8 Km. When orchards need to be sprayed with insecticides, actively nesting O. cornuta populations can be removed and kept in a refrigerator for at least four days before being brought back to the orchard. This operation does not affect their survival or their nesting activity.
Technical Abstract: Moving actively nesting populations of the orchard pollinator, Osmia cornuta, from a pollinated crop to one beginning to bloom could increase both the number of flowers pollinated and the number of bee progeny produced. Nesting shelters with known numbers of nesting females were nocturnally relocated for distances ranging from 0 m to 240 Km, and the numbers of nesting females were counted after each move. Nearly all females continued to nest at shelters that were moved short (0 to 3 m) distances. Moves of intermediate distances (135 to 235 m) resulted in considerable dispersal (30% to 76%), and many females flew back to the original nesting site. Some of these females eventually returned to the relocated shelter, so that two to seven days after the move, dispersal had diminished to 17-61%. At long distances (3 to 240 Km) dispersal was higher (63 to 78%) and no bees were seen hovering at the original site or returning to the relocated shelter. Moving distance was positively correlated with dispersal and with orientation (zigzagging) flights made by females when they first exited their nests after the moves. The addition or removal of supplementary visual landmarks (2 m x 1.5 m banner with colored patterns) at the nesting shelter did not affect dispersal rates. Bees appeared to respond to supplementary landmarks but used other signals as primary orientation cues. The homing ability of O. cornuta (maximum distance at which females were able to relocate their nest) was established at 1.8 Km. O. cornuta populations used for crop pollination can be removed and stored at low temperature for up to 4 days (e.g. to avoid pesticide treatments) and then reinstalled at their nesting site. When they are moved to a new site, dispersal rates increase with moving