Fig 7. Extreme differential conditioning of the proboscis reflex.

Frequency of proboscis extension to blue and yellow spots in Eristalis tenax fed with blue coloured nutrients and experienced differential conditioning with reward on blue and punishment on yellow colours (n = 20). Different letters denote significant differences due to a one-tailed Sign test (p<0.01). Blue t = 0min denotes the test to blue spots immediately after training, Blue t = 5min that 5 minutes later, Yellow the control test to yellow spots. The insets show the artificial flowers used in the tests.