What bee is this?

What bee is this?

Observation - What bee is this?. Description: 20 or so of these insects are living amongst the base of a bamboo in a warm, sheltered spot, now in the second year in the same place. This one is about 12mm from head to abdomen. They only fly when the sun is out and the air fairly still. Last year, we h

20 or so of these insects are living amongst the base of a bamboo in a warm, sheltered spot, now in the second year in the same place. This one is about 12mm from head to abdomen. They only fly when the sun is out and the air fairly still. Last year, we had no sign of them beyond mid summer.