Skimmers, Darters, Chasers and Damsels - Odonata Quiz

Answer: Toothed jaw

Both dragonflies and damselflies possess a fearsome battery of mouthparts of a type unique to their order. The lower lip, or labium, has been modified to consist of a pair of hinged spines that move in a sideways manner to impale its prey. When not in use these modified palps are folded away below the insect's head. Should the nymph capture large, struggling prey, dragonfly larva will use the sharp spines on the tip of the abdomen to subdue it further.

As a nymph, their prey consists of the larvae of other insects, water fleas, snails, small fish and tadpoles.

The labium are easily capable of piercing the exoskeletons of their prey and their powerful mandibles make short work of the relatively soft flesh of vertebrates. Adults catch their prey on the wing and it is not unusual to see a dragonfly dismember its food in flight with their wings bitten off and discarded, fluttering to the ground whilst the dragonfly devours the insect's body.

As nymphs, both dragon and damselflies will only take moving prey which they sense by touch or by sight.

Answer: Size

Dragonfly larvae are much larger and more robust than their smaller cousins. Damselfly larvae are more slender and much more daintily built. Additionally, damselfly larvae can be identified by examining the tip of the abdomen. These insects possess three broad paddle shaped appendages known as caudal lamellae which they use for both propulsion and breathing.

Many species live in slack or still water which often contains lower levels of oxygen and the broad flat shape of the caudal lamellae enable the nymph to absorb greater quantities of oxygen. Dragonfly larvae, on the other hand, possess five spines at the end of their abdomen. Dragonfly larvae also possess gills for breathing and the spines on the abdomen are primarily used for defence and for subduing struggling prey.

Answer: True

Unlike many other insects that go through four stages of development known as holometabolism, dragonflies and damselflies dispense with the pupal stage. The adult develops completely whilst in the larval stage. As the nymph grows in size it needs to replace the old exoskeleton, a process that the nymphs of some species may undergo up to eighteen times. Each time the larva moults it is said to enter a new 'stadium', a stage that was previously referred to as an 'instar'.

Answer: Exuvia

In order to minimise predation, especially by birds, the emergence of most species takes place at dusk, overnight and just before dawn. The larva will move from the substrate of the water course in which it may have spent up to five years to prepare for the emergence of the adult. The larva needs to spend a little time at the margin between the water and the air in order to make the transition from breathing under water to breathing air. Once it has found a suitable location the larva will ensure that there are no obstructions that may damage the wings whilst they are expanding and drying. Damage to the wings at this stage may make it difficult for the insect to find a mate at best, or it may prove fatal at worst.

Emergence begins with a split along a weak spot running through the centre of the nymph's thorax. As the adult insect's head and thorax emerge it leans backwards hesitating in this position whilst its legs harden. Once the legs have hardened sufficiently the adult pulls itself erect and grasps its support before drawing the remainder of its abdomen from the larval husk. This is a dangerous time for the newly emerged adult, known as a 'teneral'. If the adult loses its grip and falls, especially into water, it will mean certain death. At this stage the adult will pump fluid from its thorax into its wings and once these have fully expanded and hardened the adult is ready to take its maiden flight.

Answer: Paired wing

The forward pair and the rear pair of wings in the damselfly are of almost identical size and shape, whereas the dragonflies have distinctly different size and shape to each pair of wings. In the dragonfly the front pair of wings is longer and slimmer than those at the rear and from this they take the name of their sub-order, the Anisoptera or different wing. Because of the way that the wings are attached to their bodies, dragonflies are among the most manoeuvrable and fastest flying insects in the world. Some damselflies have a flight speed of up to 10 kilometres per hour whereas certain species of dragonflies travel at almost four times this speed. Those extinct species of giant dragonflies of which only fossil remains exist have been estimated to fly at almost 70 kilometres per hour!

Dragonflies move their wings at a relatively slow 30 beats per second which is not fast enough to produce the buzz typical of most other flying insects. Instead they produce a distinctive rustling and rattling sound as their wings, moving independently of each other, propel them around their territories... sit and relax near a pond or river on a bright sunny day to hear the dragonflies going about their business.

Answer: False

The grooves and ridges have evolved to facilitate mating, and each species possesses different patterns in order to prevent, or at least minimise, the possibility of inter-breeding. During mating the male will use the appendages known as claspers at the end of his abdomen to grasp the female on the thorax immediately behind her head and she, in turn will extend her abdomen to a point beneath the male insect's thorax where she will be fertilised by a small packet of the male's sperm. Mating may, depending on the species, last from a few seconds to a number of hours and can become a frantic affair - it is not unusual for the female to be injured by over-enthusiastic males! It is very easy to identify a mating couple as the form of their two joined bodies resembles the shape of a heart.

Answer: Ocelli

The ocelli, a name derived from Latin and means 'little eye', are not true eyes as such but small groups of cells in pits that are sensitive to light levels. They are arranged in the shape of a triangle with an apex facing forwards. The primary function of the ocelli is flight control and they are directly connected to the flight muscles by nerves. As the insect dives or rolls, its horizon alters and the intensity of light received by the ocelli allows the insect to make in-flight corrections.

Ommatidia is the name given to each of the individual facets that the larger compound eyes are composed of with some species having up to around twenty-eight thousand individual facets. The pterostigma and discoidal cells are features of the wings of both dragon and damselflies.

Answer: False

All species of dragonfly have superb eyesight and this does have a tendency to make them inquisitive. If you should wander into a dragonfly's territory it is highly likely that it will fly over and investigate - from a safe distance, of course. It is a common misconception that these insects are capable of biting and/or stinging. Unlike wasps and hornets, both dragons and damsels are completely harmless, unless you are an innocent hoverfly just going about your business!

Answer: Diapause

As adults, members of the order Odonata have very short lives, rarely exceeding more than a few weeks, which makes it imperative that the adults stand the best chance of meeting members of the opposite sex for the purposes of mating. The best method of achieving this is to synchronise the emergence of the adults.

The diapause is triggered by changes in the temperature and the length of the daylight hours during the summer months of the year before emergence of a given population is due to occur. During the diapause those nymphs that would have emerged during the spring months of the following year undergo a period of suspended growth ensuring that the majority of the population overwinter at the same stage of development and emerge the following year at the same time.

Some nymphs, those that have entered their final stadium before the seasonal threshold, will emerge during the summer months of the same year and extend the season in which they are on the wing.

Answer: Golden-ringed dragonfly

Apart from its large size, the golden-ringed dragonfly is one of Great Britain's most strikingly coloured insects and is unlikely to be mistaken for any other species. Overall the colouring is a deep slate blue-gray to black. The thorax is decorated with yellow stripes whilst each segment of the abdomen is highlighted with bright yellow bands.

The larvae prefer an acidic habitat and can usually be found in small moorland runnels and slow-flowing streams but never in still or standing water. It is also unlikely that this dragonfly will be encountered away from the western areas of the British mainland and, surprisingly, it is absent in Ireland.

The Golden-ringed dragonfly has a body length of between seventy-four and eighty-four millimetres and a hind wing span of nearly ninety millimetres, making it a truly impressive insect.