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.