This flower just opened today, and the petals have not yet uncurled completely. The bees on my property are busy with several other flowers right now, including Tecoma Stans 'Orange Jubilee' and Leucophyllum frutescens, or Texas Sage, so I wasn't able to gather any information today. The sunflower did have a visitor though. I think it's a Praying Mantis. It stayed motionless all day, waiting for prey. It was still there this evening.