Its coming to the near end of the Mason Bee breeding season, and here are my un-scientific findings on nest boxes for there eggs. Three sets of nesting boxes, the top 2 being plastic with a plastic screen, the cardboard tubes also being paper lined. The bottom box being a more expensive type made of compressed fibre, but with just cardboard tubes and no paper lining. This bottom box being approx 75cm from ground.
The top nesting box (in the photo below) has only 4 filled tubes, notice the mud plug in the ends. This should mean that each tube will have 3 or 4 eggs, this being about 12 cocoons. The eggs furthermost in will be females, with the males being closest to the mud plug. The males hatch first followed by the females.
Also I nearly missed that in the middle nesting box was a white grub at the entrance, which I assume to be a mason bee grub. For some reason it has come out of its tube, notice the pollen below. Maybe a bird has pulled it out ??