Complex sentence: One reason for this could be that the modification of abdominal appendages into a male copulation organ emerged later than the evolution of flight, indicated by the fact that dragonflies have a different copulation organ than other insects.
Split into simpler sentences: One reason for this could be that the modification of abdominal appendages into a male copulation organs emerged later than the evolution of flight. This is indicated by the fact that dragonflies have a different copulation organ than other insects.