24 fun facts about the fascinating dragonfly
- Credit: Archant © 2008
With dragonfly season around the corner, Norfolk's county dragonfly recorder, Dr Pam Taylor, has educated us with 22 weird and wonderful facts about the impressive insects.
1) The earliest fossil dragonflies date back 300 million years and although some in the past were monsters, their overall shape has changed little since those early days.
2) Although today's dragonflies can reach wingspans of over 10cms, some of their fossil relatives were more than seven times this size long before dinosaurs ruled the Earth.
3) Dragonflies are true survivors. Their initial design, great mobility and predatory nature have all played a part in helping these amazing creatures to cope with numerous changes to our planet's climate and structure.
4) Today there are approximately 6,000 named dragonfly species in the world. This figure is only approximate because new species are constantly being discovered and described for the first time.
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5) There are currently 55 dragonfly species on the British and Irish lists, plus two that are now thought extinct in the UK. One of these regionally extinct species is Norfolk Damselfly, and has not been seen in Britain since 1958.
6) Of the species still found in Britain and Ireland today, 46 are resident or regular migrants and a further nine are rarer vagrants.
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7) Norfolk has recorded no fewer than 38 species over the years, just two species fewer than the top area of East Sussex.
8) The large red dragonfly is the first to appear in spring, closely followed by its blue cousins; the azure, variable and common blue damselflies. Later in the season the emeralds appear. Scattered amongst these you will find blue-tailed damselflies whose females come in no less than five different colour-forms.
9) The small red-eyed damselfly first appeared in Britain as recently as 1999.
10) If you observe a dragonfly's wings in close-up you will see a network of veins that criss-cross, to add strength to their structure - as do the fine corrugations that run parallel to the leading edge of each wing.
11) Each dragonfly wing can be operated separately. A flexible joint on the leading edge of each wing allows the insect to twist more strongly as it turns.
12) The pterostigma, the thickened cell near the wing-tip, enables the insect to glide at speeds up to 25% faster than it would otherwise be capable of, before limiting vibrations caused by the airflow set in.
13) Adult dragonflies have virtually 360-degree vision, with only the area directly behind the head, where wings and body naturally interrupt the image, being unseen.
14) Each compound eye can detect colour, ultraviolet light, the plane of polarization and movement. Larger dragonflies can have up to 30,000 lens-capped units, called ommatidia, in each eye. This is what gives them their wrap-around vision and allows them to continue seeing you long after they have flown past.
15) Dragonflies are able to fly at more than 20 miles per hour.
16) Dragonflies belong to the order Odonata meaning 'toothed-ones', which contains both the Anisoptera (true dragonflies) and Zygoptera (damselflies).
17) Dragonflies hind wing is broader than their forewing.
18) Dragonflies and damselflies have three life stages – egg, larva and adult.
19) Damselfly larvae usually live one or two years in the water. For dragonflies it's usually two or three years.
20) When larvae are ready to become adults they climb an emergent plant either in or close to the water's edge, split their larval case open along the back and then extract their body and wings from the case. Once these are pumped up and hardened they are able to fly. The adult dragonfly is always much longer than the empty case (exuvia) it leaves behind.
21) On average damselflies live for one to two weeks as adults, but some of the larger dragonflies can survive for up to three or four months.
Adult dragonflies often spend a week or more foraging away from water as they mature, only returning to our waterways when they are ready to breed.
22) Damselflies and hawker dragonflies lay elongated eggs directly into plants or other organic material. Chasers, skimmers and darters scatter their more rounded eggs directly into the water or onto damp surfaces.
23) Eggs laid in the spring and early summer often hatch the same season. Eggs laid later in the year are more likely to hatch the following season.
24) Just like the adults, dragonfly and damselfly larvae are voracious predators. They feed on other insect larvae, worms, leeches and even small tadpoles and fish.
• Dr Pam Taylor is the county dragonfly recorder for Norfolk. Requests for recording forms can be sent to her via firstname.lastname@example.org.
• The British Dragonfly Society (BDS) website (www.british-dragonflies.org.uk) contains lots of information about dragonflies and forthcoming events.