Millions of them! The adult insect has no working mouthparts. It simply mates and dies within 24 hours after pupation. The predacious larvae live in water and molt several times before emerging as flying adults. Pondering over creatures like these make you realize that Darwin barely scratched the surface. Why does something like this exist? When did it not? Or did it always? Schoepenhauer said that existance is simply a matter of possibility...everything that can exist will. That's probably the best answer......the why of it has no other meaning(?).