This big event has been a long time coming. The larva, or nymph, spent between one and two years (though up to five years has been recorded) as a voracious aquatic predator, before finally taking its cues from changes in day length and water temperature.
Unlike maggots and caterpillars, which undergo a single complete rearrangement of internal organs during a chrysalis stage, dragonfly larvae grow continuously via a series of instars. Each one casts off its old tight skin to inflate, then harden, a larger skin underneath. The wing buds also get bigger with each moult. By about the 10th or 12th instar, the larva is fully grown.
In late evening or early morning, the larva hauls itself up an emergent stem, often of a reed, sedge or iris. Tightly gripping an anchor point, the larva starts to redistribute its body fluids, expanding the thorax until its skin splits down the back. Head, shoulders, legs and thorax ease out backwards, then the new dragonfly is dangling by its tail. A pause of an hour gives the legs time to harden – a chemical curing process called sclerotisation.
Clinging to its now empty larval shell, or exuvia, the dragonfly extricates its tail and begins pumping body fluids into its four wings, inflating the fine tracery of the grid-like veins. It will take several more hours until they, and the rest of its body, sclerotise enough for flight.
Did you know?
■ Empty dragonfly larval cases are often complete, except for a single exit hole located behind the head.
■ Newly emerged dragonflies take a few days to develop their full colours, which differ between males and females.
Plus, three questions on DRAGONFLY MATING answered by Eleanor Colver from the British Dragonfly Society...
Are dragonflies territorial?
Yes. The males of some dragonfly species are highly territorial. Competitors will fight viciously over prime egg-laying sites in order to attract the most females. One example is the southern hawker – a common visitor to garden ponds. If you wander into a male’s territory, don’t be surprised if he approaches and inspects you as an intruder.
Do dragonflies and damselflies perform courtship displays?
Only a very small number of UK species are known to perform courtship displays, including both the banded demoiselle and the beautiful demoiselle, two species you can see drifting along stream and riverbanks on warm summer days. The males aim to attract females by showing off large, beautiful wings in fluttering aerial dances.
Do the males tend to stick around after mating?
To an extent, yes. The males of many species guard their females until egg-laying is complete, keeping an eye out for predators in the vicinity and chasing off any overly interested rivals. In some species, the male simply flies close to the female during egg-laying; in others, the male uses ‘claspers’ at the end of his abdomen to physically attach himself to the female’s head.