Data and code for: Bee swimming is adaptive but disrupted by insecticide

A unique type of locomotion was recently discovered that honey bees (Apis mellifera L.) could propel their own body on water surface by keeping their upper wing surface dry while moving their wings. However, it was not clear whether such locomotive behavior was ecologically meaningful. Here we show that honey bees preferred a dark region (skototaxis) while hydrofoiling on the water surface in trying to reach the edge. This was shown by the significant deviation from random distribution by Rayleigh tests and also by Contingency Table Analyses. However, this skototaxis was disrupted by a neonicotinoid insecticide thiamethoxam, as indicated by the random distribution of bees landing angle in pesticide-fed bees. This change is most likely due to a loss of motor control in the intoxicated honey bees, because they made 3 times more circular turns compared to the control bees. Finally, we show that mason bees (Osmia excavata) also displayed skototaxis, showing a significantly stronger preference for dark than honey bees. The female mason bees exhibited higher efficiency than males in swimming, as indicated by their shorter duration and distances. These findings suggest that swimming behavior in bees evolved before sociality and serves important adaptive and ecological functions. However, environmental pollution from excessive pesticide use may negatively impact this behavior. 

Reuse of data is permitted. No honey bees were harmed during the experiments because all bees were returned to their colonies after the swimming tests were done. Data structure is described for each file in the readme file.

Methods
Detailed methods are described in the published paper.