Darters and hawkers all a-flicker

A rare second day of sunshine found the acre a-flicker with dragonflies, cruising around the hedges with a stiff rustle of wings. If I had spent enough long mornings at the pond, peering into its rank jungle of rushes, I might actually have seen one of these creatures climb up a stem and break out of its nymphal skin: a miraculous piece of escapology, conjuring double wings from unpromising stumps and extending a long fuselage like sections of a telescope.

The newly-emerged dragonfly is still a pale, groggy ghost of itself - the technical word "imago" seems, for once, spot-on - and liable to be snapped up by any sharp-eyed swallow. It needs a good many flights and several feeds of midges or mayflies before the wings toughen up and the vivid, intricate enamels of the body take on their full brilliance.

A field guide to dragonflies can be a work of art, but dauntingly full of Latin names, too many species which look dazzlingly alike and can be told apart only by close inspection of their genitalia. Slowly, I am absorbing the modest roster of species likely to haunt our hillside in any particular month: each species has its own short season on the wing before it mates, lays its eggs in or near a pond, and dies.

Dragonflies can be as swift and difficult as butterflies to get a really good look at, and last week's squadron were distinctly fidgety. They were darters (as opposed to hawkers), which meant that they picked a spot to settle and came back to it again and again between short, rapid dashes after prey, most of them unsuccessful.

A patient, motionless stoop over the chosen spot let me see as much as I wanted to of Sympetrum striolatum, commonest of all the late summer darters and confusing only in that, while the male has a reddish body, the female is a yellowy-brown. I found both perched on the same log. What also connects from this closer look is the extraordinary vigilance of the great compound eyes and the way the head is mounted to swivel every-which-way, even underneath and behind: an omnipercipience tensely at odds with the still poise of the body, the shimmering spread of wings.

Hawker dragonflies have a different behaviour, hunting up and down a chosen beat, perhaps a stream or canal, catching midges or mosquitoes in the hairy scoop of their front legs and often munching them on the wing. If the prey is very large, they may land to eat it: I once met the lovely male Common Aeshna, enormous and kingfisher blue, finishing off a wasp in the blackcurrant bushes.

The Brown Aeshna, of the same family, is our biggest dragonfly, almost 8 cm long, and may be seen these evenings hawking up and down the midland canals and lakes, even as darkness falls.

Ireland's wealth of bogs and wetlands ought to make a dragonfly paradise. The rules of island biogeography put a limit on our range of species, but we do, in fact, have a bigger share of many kinds of freshwater insects than of terrestrial ones. For example, we have only 40 per cent of Britain's ant species, but almost three-quarters of its freshwater insect list.

When it comes to dragonflies, the Odonata, we have 27 species (compared with Britain's 45), but that counts in five migrant species that arrive here now and then. They're all named in the new "Checklist of Irish Aquatic Insects" brought out to mark the big world conference of freshwater scientists held in UCD in last month.*

Only one is, as it were, specially Irish - and known, indeed, as the Irish Damselfly even by English entomologists. Damselflies are the dragonflies' daintier cousins that often make love in Karma Sutra positions on the lily-pad leaves in garden ponds, but the black-and-blue Coenagrion lunulatum prefers those of wilder plants in small, sheltered lakes and pools in cutover bogs with a good fringe of rushes.

It wasn't discovered until 1981, but is quite widely spread through Ireland, if still uncommon. What makes its presence odd is that it's rare outside northern Scandinavia, and Britain doesn't have it it at all, yet ours seems to be one of its largest populations in western Europe. Perhaps our cutaway bogpools remind it of its native tundra. The five migrants in the check-list conjure wonderful pictures in my mind: glittering squadrons winging through the high passes of the Pyrenees. This actually happens - it was described in a classic paper by the ornithologist David Lack. In October, 1950, he sat with his wife among the rocks at the bare top of a pass to watch the songbirds and pigeons funnelling through from France into Spain and was amazed to find an even more spectacular passage of insects.

Along with the butterflies (red admirals, clouded yellows and others) came ten times as many dragonflies: "Whenever we looked at right angles to the stream of insects, we could see at least six and sometimes twenty dragonflies in the air at once. They may well have been passing at a rate of several thousand an hour." Lack threw his shirt over some of them and found he had captured Sympetrium striolatum, male and female - just the dragonflies I was watching last week. It is a widespread species in Europe, so this may have been a purely regional migration. Most of our vagrant visitors are also species common enough in Europe and closely related to our own - a yellow-winged and a bright-red Sympetrum, a green-and-blue Aeshna, and so on.

The last one, Aeshna cyanea, is known for being exceptionally inquisitive, flying to within a metre of someone standing still. Most dragonflies are shy enough, taking wing when approached, and Ireland's rarest species, the metal-bright Downy Emerald and Northern Emerald, both found only around Killarney, are almost impossible to catch, the latter whisking up into the sky if anyone comes near.

The old names for dragonflies - horse-stingers, devil's darning needles - may have gone, but fear of these lovely insects remains. It needs saying: they have no sting. If caught in the hand, they may curl their abdomen round to touch your skin, but they have no sting. Even if you put your finger to the mouth of the largest dragonfly, it will give only the slightest of nips.

By P. Ashe, J.P. O'Connor and D.A. Murray; published by the Irish Biogeographical Society; available from Dr D.A.Murray, Department of Zoology, University College, Belfield, Dublin 4.