We no longer offer cardboard bee tubes alone. We are always learning, and we always put the health of the bees first. Here's the reason.
As you may know, we have a bee buyback program in the fall. People sell us their harvested or unharvested extra cocoons. We have found that the tubes without liners are full of wasp larvae. However, the tubes with the paper inserts are clean.
We discovered that these wasps lay their antennae down on the paper tube, and they can tell right where a mason bee cocoon is because they can feel the vibrations as the bees inside move about. Thus, they know exactly where to insert their ovipositors and lay their eggs inside the mason bee cocoon. UGH! The addition of the paper liner dampens these vibrations to the point that the wasp cannot sense where the cocoons are.
People use cardboard tubes without liners, which severely threatens the cocoons' viability by harvest time. To keep with our "bees' health first" mission, we felt we could no longer offer the tubes alone in good conscience.