Peace, that picture, on my 17" screen, comes about 110% as large as life. Just a fraction bigger than normal.

Then they turn into a bullet-shaped 'caster', which hardens into a chrysalis, which pops it's top and out comes the fly.
Tracking them from there is the problem, and why I can't sex them.
The timing of this process, at various temperatures, is of the utmost importance to CSI operatives.
Maggots feed by spitting out Pepsin to dissolve the meat, and sucking up the resultant soup.

Where do flies go in winter? They die, 99.9% of them. The chrysalis doesn't, it can be frozen solid and survive, and it is up to a foot underground anyway.

I'll bet we have some disgusted lurkers by now!