The life cycle of dragonflies and damselflies is complex and fascinating. Odonata have three distinct and quite different stages in their development: the most familiar one is as aerial insects, but their life begins as eggs and the majority of it is spent, mostly hidden, in the depths of rivers, lakes, and ponds.
Rather confusingly, there are several terms in common usage for the aquatic stage of a dragonfly’s life, and dragonfly references may call this a Larva, Nymph, or Naiad. Regardless of scientific nomenclature – the term that refers to how scientists name things – larva and nymph are the most common names used in the UK to refer to the naiad so I’ve use these terms, rather than the stricter definition of naiad.
Successful breeding results in the female laying eggs (Ovipositing), usually in water or very close to it. There is no internal gestation period and fertilised eggs are oviposited immediately following copulation.
Dependant on the method used for ovipositing, eggs may be shaped like a grain of rice (Endophytic ovipositors) or more spherical (Exophytic ovipositors). Eggs are small, between approximately 0.5 mm and 1.5 mm.
A female may oviposit hundreds or thousands of eggs at a time. The eggs usually hatch after about a month, but some species’ eggs overwinter and hatch the following spring, especially if laid late in the season.
When the egg hatches a larva emerges. Odonata larvae resemble the adult insect, and shares common features like compound eyes, six segmented legs, and (non-functional) wings. The nymph stage of Odonata does not breath air and require gills for oxygen transport.
The aquatic larva or nymph develops through a series of moults until the last which is the emergence of an adult (or Imago) flying insect – a dragonfly or damselfly, familiar on summer days wherever water is near. Dragonflies and damselflies are known as Hemimetabolous insects; they have separate and distinct stages in their lives and undergo incomplete metamorphoses – there is no pupal stage such as occurs in other winged insects like flies and butterflies for example.
The time a nymph lives underwater is much longer than the imago lives as a flying insect. Nymphs live for months and often years as they develop. They are sexually inactive and do not reproduce, and their life is devoted to hunting prey and feeding. Odonata larvae, especially those of dragonflies, are voracious predators, and will eat anything smaller than themselves.
Once a dragonfly or damselfly leaves the water to take to the air, it remains a fierce predator of other insects. They are exclusively hunters of other insects and do not eat carrion or vegetation. Its primary purpose however is reproduction.
Reproduction in Odonata is unique, with sophisticated and complex courtship rituals. Male dragonflies in particular may be very territorial and will chase off other dragonflies, regardless of species. This is less common in damselflies, but very obvious in Demoiselles.
Adult dragonflies and damselflies have a much shorter life than larvae, and usually only live a few days or weeks, months at best. Damselflies have shorter lives of a few days or weeks, dragonflies live longer and may last a few months. But unlike larvae, they don’t grow or need to shed their skin – dragonflies and damselflies are the finished article.