Fig 5. Absolute conditioning of the proboscis reflex to blue (control).

Frequency of proboscis extension to blue and yellow spots in Eristalis tenax that experienced absolute conditioning with reward on blue colours and were tested on artificial flowers offering no droplet of a liquid (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.