What happens to a fly when sprayed with fly killer?

Answer 1

Insect sprays have a high level of oils in them, so when you spray the bug, it mostly dies from effects from saturation, including too much moisture to their wings. The level of insecticide in the sprays is often not enough to kill insects that come later, just the ones you spray.

Answer 2

Most likely because the species or population of fly has undergone a mutation in the gene pool that makes them immune to the pesticide.

Many pesticides have a petroleum content that kills insects upon contact--if you don't get enough on the fly, it will continue to live.

Answer 3

It dies