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Pond Life - Dragonflies and Their Relatives

By: Dr Gareth Evans - Updated: 20 Nov 2010 | comments*Discuss
 
Darters Hawkers Damselflies Nymph

A brightly coloured dragonfly zipping across the surface of a pond is one of the iconic images of a British summer - though in some parts of the country, an increasingly rare one. Dragonflies and their relatives, the damselflies, were amongst the first things to fly, taking to the air back in the Carboniferous Era - about 150 million years before the dinosaurs appeared! Virtually unchanged since then, they have proved themselves to be a highly successful group during the intervening 300 million years or so, but more recently life has become a little more difficult for them. Over the last fifty years, with the gradual loss of more and more of their natural wetland habitats, three British species have become extinct - making the haven offered by garden ponds increasingly important for many of the 39 kinds which still remain.

The Water Dragon

Although at its most conspicuous in the air on a sunny day, most of the dragonfly's life is lived underwater, as a voraciously carnivorous nymph. In a lifespan of six or seven years in the case of some of the larger species, only around four months will be spent as a winged adult - so a good pond to call home is clearly essential!

Hatching from eggs laid directly in the water or inserted into mud or water plants, the young which emerge waste no time in finding a meal - and will continue to eat anything they can capture as they grow. The prey is grabbed in a lightning-fast lunge of a pincer-like extension of their lower jar - called the "mask" - in a scene scarily reminiscent of the "Alien" movies! Unfortunately since their varied menu can include tadpoles, small newts and fish fry, they are not always particularly popular with pond owners. However, unless they are present in large numbers, the damage they do is not so great and, in their favour, they can help to control the population of other predatory insects.

Dragonflies are unusual in that, unlike insects such as butterflies, moths and houseflies, they do not have a chrysalis or pupa stage. When the time is right, the nymphs simply climb out of the water up the stem of a plant, shed their skins, expand and dry their wings and then fly away as fully formed adults in search of food and a mate.

Darters, Hawkers and Damselflies

Dragonflies fall into two main groups - the darters and the hawkers - based on their hunting behaviour. The typical long, thin bodied dragonfly is a hawker, patrolling its patch and swooping on any likely looking prey that it comes across, while the shorter, fatter-bodied darters find themselves a good vantage point to perch on, and then dart out when food is in range. Both are superlative fliers; highly manoeuvrable and with some species having a top speed touching 30 mph, they make fearsome hunters.

Damselflies look very similar to their relatives and can often be mistaken for a less robust kind of dragonfly. However, there are a few general guides to telling them apart and once you "get your eye in", it's not too difficult to spot the differences. Damselflies are generally smaller and slighter in build, and while dragonflies can often been encountered some distance from water, the damselfly is a weaker flier and seldom strays far from its home pond. The eyes of a dragonfly are very prominent - usually so large that they wrap around the head and often touch - and a perching dragonfly spreads its wings out to the side. By contrast, at rest the smaller-eyed damselfly tends to hold its wings folded back along its body.

There are probably few kinds of native pond-life for which garden ponds can make quite so much of a difference as either dragonflies or damselflies. With so much of their lives spent lurking underwater, ponds are absolutely key to their survival - and having both pre-dated and outlived T.rex and his kin, they are probably due a little help now.

Rejoicing in a variety of fanciful old names, including Adder Bolt, Horse Stinger and Devil's Darning Needle and with a rich folklore all of its own, the true life of the dragonfly is every bit as fascinating as its mythology.

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What is the name of the dragonfly (?) that has 4 wings, skinning wing length but a box shape end that measures approx. 3/8 inch square at end of each wing ? It's brown in color with black patches over body an box wing tips.
Tinkerer - 21-Jun-11 @ 10:47 PM
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