In the topic "How do the bees remove the pollen from their baskets?" Michael Bush wrote:
Interestingly a bee can unload their own pollen, but they cannot unload their own propolis. I've seen them spend quite an long time finding someone to unload them when they have a load of propolis.
which got me thinking: "Honey-stomach for nectar, pollen sacs on the legs for pollen, where do they carry the propolis?" I realize I probably have the answer in one of the books in my library, but it is a lot more fun to ask on the forum than to actually go look it up.