Current high losses of honey bees seriously threaten crop pollination. Whereas parasite exposure is acknowledged as an important cause of these losses, the role of insecticides is controversial. Parasites and neonicotinoid insecticides reduce homing success of foragers, e.g., by reduced orientation, but it is unknown whether they negatively affect flight capacity. We investigated how exposing colonies to the parasitic mite Varroa destructor and the neonicotinoid insecticide imidacloprid affect flight capacity of foragers. Flight distance, time and speed of foragers were measured in flight mills to assess the relative and interactive effects of high V. destructor load and a field-realistic, chronic sub-lethal dose of imidacloprid. Foragers from colonies exposed to high levels of V. destructor flew shorter distances, with a larger effect when also exposed to imidacloprid. Bee body mass partly explained our results as bees were heavier when exposed to these stressors, possibly due to an earlier onset of foraging. Our findings contribute to understanding of interacting stressors that can explain colony losses. Reduced flight capacity decreases the food-collecting ability of honey bees and may hamper the use of precocious foraging as a coping mechanism during colony (nutritional) stress. Ineffective coping mechanisms may lead to destructive cascading effects and subsequent colony collapse.
Flight performance 2015-11-13
BeeNr: ID individual; Colony: ID colony;
Molaire: 1 or 2M sugar concentration fed as fuel for flight;
Varroa: treatment 0= low infestation (treated with acaricide), treatment 1= high infestation (NOT treated with acaricide);
Imidacloprid: treatment 0= control 0 microgram per Liter, treatment 1= 6 microgram per Liter imidacloprid a.i. (in 660ml sugarwater 50% per week);
FlightDate: date of the flight(s);
Flightday: day since start, first flight date;
Flightmill: ID flightmill;
N: number of rounds continuous flight;
Distancem: Distance in meters;
Log_Distancem: log10 Distance in meters;
Flighttimemin: Flight time in minutes;
Log_Flighttimemin: log10 Flight time in minutes;
Averagems: Average speed in meters per second;
Maxms: Maximum speed in meters per second;
Weightmg: Weight of the bee in milligram after the flight(s);
Winglengthmm: Winglength of front wing from the joint to tip in millimeter;
Survivalapril14: survival of the colony in April 2014 0=alive, 1=dead;
Mites 2015-11-13
Varroa: treatment 0= low infestation (treated with acaricide), treatment 1= high infestation (NOT treated with acaricide);
Imidacloprid: treatment 0= control 0 microgram per Liter, treatment 1= 6 microgram per Liter imidacloprid a.i. (in 660ml sugarwater 50% per week);
Colony: ID colony;
Succes: 0=group that did not fly, 1=groep that did succesfully fly;
numberofbees: Number of individuals that was tested;
Mitesgrambees: Number of phoretic mites per gram bees in October 2013;
LNmites: Natural log of (number of mites per gram bees + 0.01);
Weights and Wings 2015-11-13
BeeNr: ID individual;
Colony: ID colony;
Varroa: treatment 0= low infestation (treated with acaricide), treatment 1= high infestation (NOT treated with acaricide);
Imidacloprid: treatment 0= control 0 microgram per Liter, treatment 1= 6 microgram per Liter imidacloprid a.i. (in 660ml sugarwater 50% per week);
Flightmill: ID flightmill;
Weightmg: Weight of the bee in milligram after the flight(s);
Abdomenmg: Weight of the bee's abdomen in milligram after the flight(s);
Thoraxmg: Weight of the bee's thorax in milligram after the flight(s);
Winglengthmm: Winglength of front wing from basicosta to tip in millimeter;
Successful flights 2015-11-13
File contains the data for the Chi-square test on the comparison of the number of bees that successfully flew the first and second flight.