Tuesday, June 9, 2009

Nature's Way "Dragonflies"

Dragonflies are one of nature’s miracles – beautiful, elegant and exceptionally skilled in flight, yet they emerge from aquatic larvae which are so ugly and scary-looking that they were once likened to dragons. During summer they can be found all over Britain, particularly around fresh water. Two types of insect are classified as ‘dragonflies’ – damselflies and true dragonflies. True dragonflies hold their wings perpendicular to their bodies, whereas damselflies hold their wings swept back alongside their abdomen.
Damselflies are generally more dainty – if the body of the insect is thinner than a matchstick, then it’s a damselfly. Damselflies belong to a sub-order known as zygoptera, a Greek word meaning ‘paired wings’, reflecting the fact that their wings are folded parallel to their bodies. The true dragonflies belong to the sub-order anisoptera, Greek for ‘different wings’. A true dragonfly’s wings are outstretched – in this position you can see that the fore wings are different from the hind ones. All dragonflies are carnivores at every stage of their lives, although their techniques for catching prey vary. Damselflies will attack small insects on vegetation – easy prey such as aphids are substantial enough to provide a satisfying meal. Dragonflies, on the other hand, look for something more substantial and will capture insects, including damselflies, in mid air. Different types of dragonflies have different strategies. One group, known as ‘the chasers’, will rest on a perch and wait for passing insects – if one comes close, it will chase it! Another group, known as ‘hawkers’, remain airborne and regularly patrol the edge of their territories, picking off insects that enter their ‘airspace’. Most species have claspers with which a pair join together when mating. In order for the female to receive the male’s sperm, a pair of dragonflies must form a ‘wheel’ in which the male takes hold of the back of the female’s neck and the female lifts her tail to meet the underside of the male. In some species the male keeps hold of the female while she dips her fertilised eggs beneath the surface of the water and attaches them to vegetation, often completely submerging her. You may be surprised to learn that dragonflies aren’t only found near water – they are only tied to waterways in their adult form while laying eggs. Newly emerged dragonflies tend to leave water to find shelter in thicker vegetation and larger species, such as ‘hawkers’, can spend much of their hunting time in woodland or heath. There are about 5300 different species of dragonfly around the world, and of these only about 38 regularly breed in Britain. We also get some migrant species, particularly in southern Britain. Some of these, including the red-veined darter, lesser emperor and migrant hawker, were once only found as migrants but now breed in the south of England. Others, such as the scarlet darter and yellow-winged darter, have found their way to Britain only very occasionally from Europe. Amazingly, a green darter made its way to England from America, assisted by Hurricane Earl, in September 1998. Dragonfly watching has grown in popularity in recent years. There’s been a growing tendency for birdwatchers to become interested in this area of our natural history, as during the summer there tends to be less happening in the bird world. Possibly because of this there is also a growing appetite for ‘rarity-seeking’, so we now have a national rarities committee, organised by the British Dragonfly Society, to assess the validity of rare dragonfly records. Just as in the birdwatching world, there are some observers whose only desire is to find rarities and others who would prefer to contribute to our knowledge of the subject by surveying dragonfly sites. When undertaking surveys, records of all stages of a dragonfly s life cycle can be recorded, but the most significant stages are the underwater larvae and the exuviae (the skins left by emerging insects) since these prove breeding at a location has taken place. If you’d like to learn more about these insects or become involved in recording them, then check out the British Dragonfly Society website (dragonflysoc.org.uk) TheTamshee says: if you are interested in these fine insects they get yourself on the Coire Loch - Dog Falls trail in Glen Affric, there is a a stunningly beautiful walk through the ancient Caledonian Pine Forest. A pretty waterfall in a rocky gorge, rare wildlife, a lovely loch and a superb view up the glen. The area is also a breeding site for 14 different species of rare dragonflies, so get your hiking boots on and enjoy.

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