T - maze ( light vs dark )
24h before the experiment , anesthetize 3 - 6 d old flies under CO2 , and clip 2 / 3 from both wings to half of them .
In the same vial , place around 30 flies with clipped wings and another 30 intact flies .
Let them recover from anaesthesia until experiment begins .
Place the flies in the entrance tube ( see figure ) and let them adapt for 10 min .
Turn on the light source .
Transfer the flies to the elevator by gently tapping the apparatus , and pull the movable part down in order to close it .
Flies are kept in the elevator for 30 sec .
Pull down the movable part , so that the elevator is placed between the transparent and the opaque tubes .
Allow the flies to choose between dark and light for 30 sec .
Close all tubes by pulling up the movable part , in order to lock the flies in the tube they have selected .
Count the number of flies with and without wings in each tube .
Calculate the Choice Index ( see Guidelines for formula ) .
