Bee on Lavender

I had a hard time choosing which photo to post today. I chose this one because I have a question for anybody who knows bees better than I do. What is that circular area on the side of this bee? I thought it might be the bee's ear or tympanic membrane but I couldn't find any photos that confirmed that. Anybody know? I took this during a short walk that Arvin and I took this afternoon.

I replaced the original with one done on my computer instead of my iPad. And in the extra photos is the one I was thinking of using instead of the one I did.