Another Life: It took 10 straight days of sunshine and some warm European winds gusting through the mountains, but at last, at the flower-bed beside the garden tap, Macroglossum stellatarum delivered itself to my ecstatic gaze, writes Michael Viney.
A first encounter with a migrant hummingbird hawkmoth has to be a revelation: the hovering wings an amber blur, the amazing tongue arching out like a long, fine fishing rod, sucking nectar from the heart of a flower.
Over the years, I have had so many accounts of a "strange insect" that produced a magic, awestruck moment in somebody's garden. Now it has happened in mine.
The moth fed intently at tall clumps of dame's violet, a sweetly-scented, half-wild plant that sows itself like a weed in my silty soil. It shared the lilac flowers with a red admiral - one of several to have set up their territories on the acre - and arrived within days of our first painted lady butterfly. Such a gathering promises a vintage summer for migrants, if sun and wind hold their form.
Almost every June brings a few reports, but the last invasion of the hawkmoth was in 2000, when a Co Wicklow observer counted no fewer than 84 of them, all whirring away at clumps of red valerian along the coastal railway line: an amazing spectacle. In Belfast, an ornithologist found one in his hallway, prodding at bright colours in a display of foreign banknotes mounted on the wall.
In motion, the moth does give a fair imitation of the world's tiniest and most agile bird. At rest, it becomes a large, stubby moth with very dark brown, narrow front wings that cover a pair of amber ones.
In hovering, a muscular click mechanism sweeps them obliquely up and down through a small angle at 50-70 beats a second. At the tail, a striking black-and-white chequerboard of lengthened abdominal scales serve as ailerons to help in holding the moth's position.
Its aerial ability to stay on target makes it one of several wild creatures to interest the scientists and engineers of military and naval research. As one American report on "high-lift biorobotics" puts it, the moth achieves "more stability and less heave, pitch, yaw, torque, drag and cavitation than man-made machines have yet been able to approach". Those other miraculous aerialists, the hoverflies and dragonflies, have also become model organisms for designers of missile guidance systems. Their instinctive strategies for intercepting moving targets, whether mates or prey, have prompted research papers sprinkled with intricate mathematical formula, all dealing with something called "motion camouflage". Put crudely, this is a way to reach you with something you thought was still motionless and a long way off.
The mathematical problem of optimal interception of one moving object by another is almost as old as human warfare. Leonardo da Vinci considered it, apparently, and the first serious treatment of "pursuit curves" came as early as 1732.
Nature's stealthy strategy of motion camouflage was first described in 1995 by researchers at the Australian National University's biorobotics laboratory. They had been filming the flight paths of male hoverflies tracking females through their territory.
Each summer has found me spellbound, sometimes for minutes on end, by the hoverflies' aerial manoeuvres, often made all the more striking by metallic armour that turns them into glinting points of light.
They can fly backwards and sideways as well as up and down, and their switches of position between hovering, mid-air stillness are so abrupt and rapid as to seem, sometimes, like acts of bilocation, deceiving the human eye.
Dragonflies, too, show the same intricate patterns of fixed position and trajectory when they are duelling over territory or shadowing their prey.
Their manoeuvres are designed to keep them on a path directly between the moving target and a fixed point in the distance. While, inevitably, they loom in size as they approach, they seem not to have moved in any lateral way.
Since the recognition of motion camouflage, British researchers have tested the concept on humans, in a computer game involving missiles to be shot down: those using the stealth strategy got far closer before detection.
The first American paper on "steering laws for motion camouflage" in relation to missile guidance was published a year ago.
Meanwhile, the day-flying hummingbird hawkmoth has already been joined in the Irish summer by its nocturnal counterpart, the convolvulus hawkmoth (see Eye on Nature). Honeysuckle, petunia and tobacco plants (Nicotiana) are some of the deep-throated flowers that invite hovering attention from both at different times in the 24 hours.
They lay their eggs, however, on quite different plants as food supplies for their caterpillars. Macroglossum chooses lady's bedstraw, the sweet yellow-flowered froth of hedgebanks and sand-dunes, while Agrius convolvuli seeks out the bindweed that gives the moth its name. The caterpillars of both may reach the larval stage by late autumn, but there is so far no reliable evidence of their emergence into flying moths.