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.