The life cycle of dragonflies and damselflies consist of three distinct stages:
The eggs are tiny (<0.75mm) and are either laid singly on the inside of the stems or leaves of aquatic plants, or in clusters into water or wet mud. In suitable temperatures the eggs can hatch in 2-5 weeks. However, eggs laid in autumn may enter a period of suspended development due to low temperatures and will only hatch the following Spring.
Once hatched, the larvae moult through between 6 and 18 larval instars. Dragonfly larvae are larger and more robust than damselfly larvae. As in the adults, the eyes of damselfly larvae are set far apart.
Larval development typically lasts one or two years but can take just a few months in some damselfly species, up to 5 years for the Golden-ringed dragonfly. Larvae feed on freshwater macro-invertebrates and even small fish.
Newly emerged adult dragonflies and damselflies are termed ‘tenerals’. Tenerals are very delicate (and should not be handled), show little body colouration, and have a distinct sheen to the wing membranes. The teneral stage lasts about a day but in some species it can take up to two weeks for adults to achieve their mature colours.
Newly emerged adults seek out areas away from the water in which to feed and roost. Damselflies are the most likely to congregate in sheltered areas close to the breeding site. Dragonflies are likely to disperse more widely and hunt as single individuals in sheltered woodland.
When adults reach sexual maturity they return to water to mate and lay. Males tend to monopolise the areas around the breeding pools, with dragonfly males typically exhibiting territorial behaviour. The adults feed on smaller insects but may also take smaller dragonflies and damselflies, butterflies and bees.
In poor weather and low temperatures, dragonflies and damselflies cannot fly and will rest in a variety of vegetation. Dragonflies and damselflies are predated upon by birds, spiders, frogs and newts. They may also be consumed by carnivorous plants.
The duration of the flight period for most Irish species is 15 – 22 weeks, but most individuals die within a few days of emerging due to weather and predation.