Q & A

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Eric Vinje

Hi Scotty –

Fly parasites are shipped still developing inside fly pupae and are mixed with wood shavings for protection. Depending on the temperature during shipment, they will start hatching upon arrival. (The tiny “ant like things” you saw when you first opened the bag were the first to hatch.) When you notice some hatching in the bag start releasing them as close as possible to the suspected fly breeding sites or where maggots are found (flies need some moisture to breed). Simply sprinkle the contents out of the bag out over the entire breeding site(s). Do NOT release all in one spot and make several releases throughout the entire fly season.

Note: The parasitized fly pupae will not change in appearance. The tiny parasites simply exit through a small hole and begin their search for more fly pupae. Keep in mind, that the parasites must find fly pupae to continue their life-cycle. This need provides a natural and strong incentive to seek out and destroy filth flies.

I’ve included a link — with a life-cycle diagram — that should help.


Good luck!