Wasp nest

The weather is hot today, currently 99F/37C. I was about ready to surrender to the sun and had resorted to taking a photo of a thermometer I had placed on one of a row of bamboo stakes supporting my tomato plants. Then I looked at an adjacent stake and discovered this interesting activity. The wasp was bringing bits of dried grass and other vegetation to stuff in the end of the hollow stake. It was very busy doing this for a few minutes. Then it started flying up and down the stake and seemed interested in a crack in the bamboo which was a bit too small to admit its body. Next it began at the top of a stake and spiraled down to the bottom investigating it thoroughly. Having done that it did the same to the next stake and two or three others.