We are Mason bee guardians

This photo shows our Mason bee nesting box - the thing below, and the tubes for the bees to lay their eggs in. We received our pupa earlier in March but have started to put them in the nesting box just recently, now that it's warmer and with blossom out for the bees to feed on.
This is our second year and our 20 pupa last year evidently resulted in over 100. The scheme works beautifully; we send our tubes back in the autumn, they 'harvest' them to release the live pupa and distribute these to all guardians. 
It's a fascinating occupation to have; we check our pupa to see if any have hatched. Later we see the bees crawling into the tubes, which can become covered in pollen. Sometimes we see the bees reversing out which is very amusing!