In an occasional series, ALAN GANE MBE looks at the flora and fauna of the Lake District. This issue: dragonflies.
Dragonflies are among the largest and most striking insects, and are most commonly found in the vicinity of still or slow-moving water such as streams, ponds, tarns and some lakes. Within the group there are strong and robust dragonflies, hawkers, darters and skimmers, as well as the daintier and slimmer damselflies.
Large prominent compound eyes dominate the head, there is a relatively short thorax and generally long abdomen, which is particularly slender in the damselfly. Each insect has two pairs of wings, each pair being able to act independently and as a result the degree of speed and manoeuvrability is remarkable; they have rapid acceleration and can fly forwards, backwards and sideways. Each of these attributes is invaluable as they predate upon other insects in flight and sometimes on each other. The wings are dazzlingly bright and gauze-like, while the cylindrical and segmented body is often brightly coloured. They are most commonly seen on bright, warm and sunny summer days.
They may sometimes be seen bobbing up and down repeatedly along the shallowest of water margins, where they constantly dip the end of the abdomen into the mud just below the water surface. This is the process of egg-laying, although eggs are sometimes laid on the leaves or stems of water plants instead, in a similar manner. The resulting larvae generally spend eight or nine months in the water before pupating; far longer than the life span of the adults. Unlike the adults of most species, the aquatic larvae are mostly dull brown, but like the adults they are voracious predators. Generally slow at moving about on their legs, preferring to lay in wait for passing prey, when faced with danger the larvae are able to dart forwards by suddenly compressing their water filled abdomen.
The larvae moult a number of times and as the somewhat indistinct pupal stage is reached the insect climbs out of the water, usually up the stem of a plant; further development then takes place within the 'skin', which then splits down the back and the adult virtually ‘backs out’. The new adult, or imago, slowly extends its crumpled wings and takes to the air, leaving the empty husk behind.Some 40 species occur in Britain, with abdomens ranging from 22 to 65mm in length, one of the largest being the golden ringed dragonfly (illustrated), which is one of those occurring in the Lake District.
Colour varies greatly between species and there are various combinations of brown, gold, blue, green, red and black. Do look out for dragonflies in appropriate habitats and listen for their buzzing flight.
19 September 2016 by George Fisher
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In a regular series, ALAN GANE MBE looks at the flora and fauna of the Lake District. This issue: the adder