When a fly is exposed to extremely cold temperatures in a freezer, it can enter a state of suspended animation or temporary dormancy known as torpor. The exact time it takes for a fly to revive and regain normal functioning after being in the freezer depends on various factors, including the species of fly, the temperature of the freezer, and the duration of exposure.
In general, small insects like flies can recover from the effects of freezing relatively quickly compared to larger animals. Under ideal conditions, it may take anywhere from a few minutes to a couple of hours for a fly to revive and resume normal activity after being removed from the freezer.
However, it's important to note that prolonged exposure to freezing temperatures can be lethal for insects, and the recovery rate can vary. Additionally, flies that have been frozen and subsequently thawed may experience physical damage or other adverse effects that could affect their ability to survive or function normally.
If you have inadvertently placed a fly in the freezer and are concerned about its well-being, it's best to allow it to warm up naturally and provide a suitable environment for recovery.