I live in the South of England. It is currently winter.
Whenever I buy bananas, even one, if I leave the discarded banana peel in my kitchen, within hours or even minutes, there is a cloud of little flies to be seen in the vicinity.
Given that this doesn't happen with other fruit such as apples, I hypothesise that these flies spontaneously generate in the presence of opened bananas and/or their peel.
Bananas are not native to the British Isles and are imported from hot countries.
I can go months or even years without purchasing a banana and yet, when I do, these flies appear almost immediately. They also disappear almost immediately when I dispose of the fruit and its peel.
The flies do not appear until I unpeel the banana.
How can I disprove my hypothesis of spontaneous generation?
Note: A secondary hypothesis is that fruit fly eggs are distributed all around the world (including in my kitchen) and simply waiting for a banana to appear. This seems less likely but more difficult to disprove. If this is so, how do the flies have time to mate and lay the next generation of eggs in my kitchen when the banana detritus is disposed of almost immediately.