Mostly to Kearns:  These are not the bar-code references but
two articles of possible interest are in the Journal of Apicultural
Research  Vol. 29, No. 1.
        Marceau et al.  THE RELATIONSHIP BETWEEN HIVE PRODUCTIVITY AND
HONEYBEE FLIGHT ACTIVITY
 
        Liu et al.  AUTOMATED MONITORING OF FLIGHT ACTIVITY AT A BEEHIVE
ENTRANCE USING INFRARED LIGHT SENSORS
 
        Both have related lists of references.