How they breed and feedů

Biology

Dragonflies and damselflies are beautifully adapted for flight, having powerful muscles directing their four wings independently from one another. They are incredibly agile and manoeuvrable insects, able to hover, glide, fly forwards, backwards and sideways. They can also change their direction and speed of flight very rapidly.

As with all insects, their bodies are made of three basic parts: the head with multi-faceted eyes, the thorax to which the four wings and six legs are attached, and the abdomen with its ten segments.

Diagram Dragonfly body parts -Common Darter Sympetrum striolatum female

Diagram Dragonfly body parts -Common darter Sympetrum striolatum female
© BDS/J.Stevens

Life Cycle

Dragonflies and damselflies have a fascinating life history. Most of their life is spent underwater, first as an egg and then as a larva (or nymph) and they have a comparatively short adult life, being “on the wing” for a few weeks only.

For most species the whole process takes one or two years, and it begins with an egg. Eggs are laid in the vegetation, mud, or directly in the water of rivers, ponds, lochs. After a few weeks or months, depending on the species, the eggs eventually hatch out into larvae (or nymphs). The length of time spent as a larva underwater depends greatly on the temperature and availability of food. The larvae shed their skins many times to grow to full size, and developing ‘wing buds’ can be seen as they near maturity. Most damselflies take about a year to reach adulthood, whereas larger dragonflies may take two or more years.

Damselfly larva –Azure Damselfly Coenagrion puella

Damselfly larva –Azure damselfly Coenagrion puella
(© Steve Cham) Note the three leaf-like gills at the end of the abdomen

Dragonfly larva –Hairy Dragonfly Brachytron pratense

Dragonfly larva –Hairy dragonfly Brachytron pratense
(© Steve Cham) Note the absence of external gills at the end of the abdomen

When fully grown, the larva climbs out of the water onto a leaf, twig or stem, and begins its “emergence”. Its skin splits behind the head and on top of the thorax. With a slight struggle, the young adult will emerge out of the old larval skin, which is left behind. The transformation from underwater larva to winged adult is a vulnerable stage and takes place over a few hours. Soon after emergence, young adults with their pale colouration and shiny wings tend to leave the water body and will not return until they are ready to mate. The delicate, empty larval cases left behind, called “exuviae”, can be identified to species level just like larvae themselves, and constitute the ultimate proof that a given species is breeding at a site.

Downy Emerald Cordulia aenea – young emergent with exuvia

Downy emerald Cordulia aenea – young emergent with exuvia
© BDS/J.Stevens

Once the young adults have matured and gained their full colours, male and female are ready to mate. Mating, depending on the species involved, takes place in the air, or on the ground, or amongst reeds or high up in the branches of a tree. Males use claspers (or “anal appendages”) at the end of their abdomen to grab females just behind the head. When ready, the female curves her body forward so that her reproductive organs reach those of the male. This forms the “wheel” or “heart” position, which is held from a few seconds to several hours depending upon the species.

Common Blue Damselflies Enallagma cyathigerum in cop’

Common blue damselflies Enallagma cyathigerum in 'cop’ (copulation)
© BDS/J.Stevens

After copulation, the pair is still perfectly capable of flying when linked or “in tandem”. The females of some species lay their eggs while still in tandem with the male. Others may separate after mating and the female is either left to lay her eggs alone or guarded by the male flying in close proximity, protecting her from disturbance by rival males. Some species deposit their eggs directly into the water, while others insert each individual egg into leaves, stalks or rotting wood floating on the water’s surface. The females of some damselfly species can even submerge themselves totally to lay their eggs into water plants. The eggs eventually hatch and the life cycle starts all over again.

Predators and Prey

Dragonflies and damselflies are voracious carnivores. When hunting for food, adults will take any flying insects they can catch, such as flies, midges and mosquitoes. The larger species will also eat butterflies, moths and occasionally smaller dragonflies or damselflies! Adults use their excellent eyesight to detect prey. In flight, they hold their bristly legs in a basket shape to scoop up and then firmly grasp their targets before eating their catch.

The larvae of all British dragonflies and damselflies are fierce underwater predators. They catch and consume anything which is smaller than they are, either by careful stalking or ambush. Prey may include bloodworms, water fleas, tadpoles and the larvae of mosquitoes or other aquatic insects. The larger dragonfly larvae may even catch and eat small fish! Dragonfly larvae have a remarkable tool at their disposal when hunting prey: their lower lip is modified into a long, hinged jaw terminating in two sharp, hook-like mandibles. This is known as the “mask”. When a prey is in sight, the mask is thrust forward and the prey instantly impaled on the hooks, then drawn back to the mouth and eaten. The shape of the mask can vary greatly between species and is an important feature in larval identification.

Among the species that catch and eat adult dragonflies and damselflies are birds (like the hobby); spiders, as many adults get caught in webs; frogs; and larger species of dragonflies. In the larval stage, their predators include fish, frogs, toads and newts, wildfowl, as well as other aquatic invertebrates such as water scorpions, diving beetles.