Common blue damselflies appear in mid to late May and their flight period lasts right through the summer months to September. Adults live for around 12 days on average and in this short period they must breed. Mating can take up to 20 minutes and the females lay their eggs in the tissue of plants both above and below the water line and are capable of remaining submerged for some time. The male will stay guarding her at the point where she entered the water. Damselflies and dragonflies spend the greater part of their lives as larvae, sometimes as much as three years. The larvae are predatory hunters, feeding on other water creatures that also lurk amongst the waterweed. When ready to emerge, the larva climbs up a plant stem free of the water and, once the insect's outer case has dried and split, the final perfect damselfly frees itself from the chrysalis by arching its body backwards. Once free, the adult insect pumps blood into its wing veins until the wings are fully expanded.