Non-uniform distribution of treated sucrose solution via trophallaxis by honeybees affects homing success variability and mortality

Abstract

Background: Food sharing in a group via trophallaxis might lead to a non-uniform distribution of pesticide spiked sucrose solution between caged honeybees. This can cause high variability in the homing success rate or mortality among group members and treatment replicates. In order to improve the oral food distribution of tested sucrose solution we compared two feeding schemes with two or ten bees per cage (20 μL/bee) and evaluated the impact on homing success rate and mortality. Results: First results showed that food intake with the two-bees feeding regime is faster. Therefore, a more accurate dosing distribution among bees can be expected. We measured a less variable homing success rate and retuning time among runs and the corresponding treatments. Furthermore, mortality rate of the groupfeeding scheme with ten bees per cage resulted in higher mortality values when compared to the two-bees feeding scheme. This might be an indication for a better and more uniform distribution of the treated sucrose solution among two caged bees. Conclusion: Improving the uniform distribution of test items by orally treatment administration in smaller groups with honeybees should be discussed and considered, as toxicity endpoints of single-dosed wild bees are compared with group-dosed honeybees. Furthermore, to minimize the trophallaxis dependency regarding food distribution in group dosed honeybees.