I'll have to try the auger hole trick. FYI, for critical trials, we often use bold, colored shapes attached to each hive - both the color and shapes vary, so that we provide two types of visual cues. That said, I suspect that the drift to strong colonies may be attractant to a pheromone - and maybe less aggressive guard bees. Some colonies let anyone in the door. When we mark and release bees at a distance from the beeyard (using a different color for all 4 compass directions), we see the marked bees heading to the strong colonies - and bees of all 4 colors end up in the strong colony). Jerry *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html Guidelines for posting to BEE-L can be found at: http://honeybeeworld.com/bee-l/guidelines.htm