Have these patterns shown up only in your observation hives? Perhaps only on the side towards the (stronger) light source? I am reminded of a moire pattern when I look at the cells, and I wonder if the effect is unique to an observation hive environment, and would not appear in a normal (dark) hive or an observation hive with a cover over the glass. Consider the heat more than the light. jim (who hopes he sheds more light than heat) :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::