I photographed this fly on September 19, 2007 at 48.163552N 53.966826W (WGS84). The temperature was about 20 Celsius. The sun was at about the 5 o'clock position if the direction the fly was facing is referenced as 12 o'clock. Don't be fooled by the shadows, I used flash. In fact, the instant the flash fired, the bubble collapsed and the fly immediately withdrew the substance into its mouth.

Here is the entire fly: