They take several years to mature, but if already large it may emerge this summer.
They need easily accessed plant stems or similar to climb out of the water. Then the nymph's skin splits and out comes a dragonfly. It requires several days in order to harden, colour up and develop the ability to fly properly.
Birds very efficiently pick them off at this stage unless they are not accessible to them.
They are pretty voracious predators and will eat a lot of sizeable prey such as young amphibians and fish.