Two hives, both doing well, verified eggs, larva and capped brood, two 10 medium brood boxes each, with the bottom one's @2/3 full. Moved a single "starter" frame with some small comb (doing foundationless) into the upper box when I added it a little over a week ago. Both have steady waves coming and going with foragers. I have screened bottom boards, and often lay under the elevated hives to watch. I have noticed that sometimes, as a whole, the bees will "shiver" as a group for just a few seconds, then stop. They are scurrying about, then all the sudden that shiver will happen. Its not the waggle dance, and seems to "light up" the whole lower cluster. Anyone know what this kid of behavior is?