Future of insects is in the hands of children

One of the lesser crises of this overheated summer has involved a vegetable wholly iconic to the serious food gardeners of these islands: the runner bean. As the July heatwave drew to a pause, a Saturday issue of The Guardian [itals] newspaper carried half-a-dozen letters discussing the apparent failure of abundantly- flowering runner beans actually to set their pods.

This was clearly an affront to Britain's army of allotment holders and back-garden wigwam builders, but an e-mail from a Sligo friend brought the anguish nearer home: no bean had set in his garden or tunnel, despite nearby bee-hives and plenty of bumblebees —- how were mine doing? Fine, I decided, burrowing into the fleecy green of a towering thicket in the tunnel and checking the first clusters of climbing French beans (not runners, it's true, but close enough).

One or two of the Guardian [itals] letters could boast of record harvests. Others offered helpful notions: runner beans need flies to pollinate them and these had vanished in the heat (all untrue); do what grandfather said and spray the flowers on dry afternoons ("complete waste of time" says my favourite, tetchily- scientific, gardening book). Or, as the Royal Horticultural Society had concluded: "Warm temperatures, especially at night, may inhibit bean formation by preventing pollen grains from germinating. Cropping should resume when cool nights return in September."

None of which quite explained the different behaviour of Sligo and Mayo beans. But the quest led me on into the preoccupied world of bumblebee and honeybee, prime agents of bean pollination. Not only are runner-bean flowers constructed to yield only to the burliness of bees, but, as one study observes, "a bee can reach the nectary with its proboscis only by standing on the left wing petal.". Even then, it needs a long-tongued bumblebee to reach the nectar vessel by a frontal approach.

Short-tongued bumblebees (including two of the commonest) habitually go round the side of any flower with long tube to its corolla, and bite a hole in it. This lets them steal nectar without brushing against the flower's pollen, thus cheating on the whole principle of cross-pollination. A runner bean flower is only viable for fertilisation for one day, and checking if it has been pollinated properly means looking for a bee's "footprint" on its front doorstep —- characteristic scratches on the delicate wing of the flower (don't you love science!).

Pollination is vital to the quality of some 40 of our fruit and vegetable crops, and almost as many more need it to set seed for future propagation. As growing of soft fruit moves into tunnels, artificial hives of bumblebees are brought in with them, so that strawberries, for example, are not only ready out of natural season, but sure to be perfectly formed.

Out of doors, bumblebees take to the wing in cooler temperatures than honeybees, so that growers of early-flowering field crops of tree fruit and soft-fruit are now offered artificial, rain-proof and badger-proof hives of European bumblebees by a Dutch company, Koppert.

All this is happening as our native bumblebees decline, mainly through loss of rural habitat, and as our 2,000-odd beekeepers battle with varroa, the mite-borne sickness introduced with imported honeybees.

The vital importance of Ireland's insects and invertebrates of all kinds, not merely to pollination but to the whole natural ecosystem, hardly needs stating. Yet what was to have been the first major Irish conference on invertebrate conservation has just been postponed. Icon, organised by the Ulster Museum and backed by conservation agencies north and south, was to have been held in Queen's University Belfast on September lst and 2nd. Now it has been put off for lack of bookings.

Perhaps we need to start at the other end of the age continuum, with children. And for that I can recommend a new and splendid photographic exhibition, "Butterflies and Little Eyes", currently on show at Enfo, in Dublin's Andrew Street (until August 19th), and soon to travel around the country. Its close-up photographs, of everything from shield-bugs and spiders to beetles and dragonflies, are the work of Dr Diarmuid OÓ Grada, a Dublin planning consultant with a fine eye for the smaller majority of wildlife.

My own appreciation was heightened even further last week when, stooping to harvest my garlic on a sunny afternoon, I was perched upon repeatedly by a large and lovely dragonfly, a moorland hawker with a body jewelled in blue. Between hunting trips up and down a clearing walled by hedges and trees, jinking occasionally to snatch a fly, it chose to rest on the back of my shoulder, glittering just out of focus of my desperately squinting eye.

It may have taken my pale green shirt as a boulder or tree-trunk. But the close, rustling whirr as it took off is stored away as a sort of lucky echo from another and parallel soundtrack of the world.