The effects of insecticides on honey bee pattern categorization ability and memory

Honey bees are the most crucial pollinators in the world, pollinating 80% of flowering crops in
the U.S. and generating 18 billion dollars of revenue. However, the honeybee population is
declining; the most detrimental cause being neonicotinoids, a synthetic insecticide used in plant
health. To understand its negative effect on honeybees, this research has designed a free-flying
system simulating the real world environment to analyze the effects of neonicotinoid
imidacloprid on honeybees' pattern categorization ability, an important cognitive function related
to their foraging behavior. In addition, this research identified which phase of memory is
impaired by imidacloprid. Using a self-designed Y-maze, a series of experiments including
training and transfer tests were systematically designed to test three groups of honeybees with
forty different patterns from five categories. In training and initial transfer tests, the results
indicated that honeybees were able to categorize signs based on feature(s) not template with a
success rate up to 90%. In imidacloprid experiments, it was concluded that medium-term
memory was negatively impacted due to decreased transfer tests performance (p< 0.05) compared
to the control group. This research went beyond traditional associative learning or basic motor
functions, it focused on honeybee’s cognitive behavior of pattern categorization in a free-flying
paradigm. Ultimately, the negative effect of imidacloprid discovered in this research should raise
community awareness about this issue, promote decreasing the usage of insecticides and
simultaneously develop an new insecticide which is environmentally friendly to honeybees.