I don't know if this will actually help anyone but I came across this a couple years ago. The Blue bottle fly is often used as an indoor plant pollinator. I know, flies and pollination, absurd sounding right? I have seen this if you believe me. Bottle flies flying from flower to flower and drinking or eating whatever they were after. This has to help pollinate flowers. The fly is also something that can be used in green houses in large numbers without the worries of getting stung. http://www.forkedtreeranch.com/flylarva.htm That is the site where I found out all this from. Hope this helps someone with their greenhouse ambitions. I know I will try it when I finally buy a house and can set up a nice greenhouse or a green room. They can also be bred but it is kinda nasty so I don't know if I will ever try it. It would result in having plenty of flies year round but the idea of rotting meat in my greenhouse is not a pleasant one. Not to mention possible health problems.
