Some settlers have six legs

Nowhere has this shrouded, muggy summer seemed more natural to the landscape than among the exotic gardens of our south-western peninsulas, planted for a century or more with shrubs and trees from New Zealand and other southern Edens. It was with only modest surprise that friends, holidaying near Parknasilla on Kenmare Bay, heard 14-year-old Kieran observe that that thing on the heather by Dad's feet had to be a stick insect.

Almost 10 years ago, as it happens, in the early days of An Eye On Nature, a Kerry reader spotted stick insects on a house wall in almost the same locality, within a hop-skip-and-a-jump of Rossdohan Island, a private garden linked by a bridge to the mainland. This collection of tree ferns, lily-of-the-valley trees and other handsomely outlandish southern hemisphere plants was originally created in the 1870s and replanted at the middle of this century (by the Walker family, who keep Fernhill in Co Dublin). Stick insects, the Phasmida, not content with imitating slender twigs or leaves, scatter tough little eggs which look like seeds (sometimes exactly like those of the host plant). It can be many months before the egg's lid pops open like the hatch of a space-capsule to release the infant insect. Over time, this neat device has served quite incidentally to carry some of the 2,700 known Phasmida species to new homes across the world.

Most of them are tropical, and so would not survive here. But three New Zealand species have established small colonies in these islands, in warm, humid places like the Scilly Isles - and, it seems, around Rossdohan. Two are prickly stick insects (with sharp spikes on the head and thorax), and one, Clitarcus hookeri, a smooth variety that has also made its home in Kerry - "like a twig that had not quite died", as my first correspondent described it. His record was doubly interesting because he saw two insects on the wall, on separate days, and the second, far smaller, could have been a male, rarely sighted outside New Zealand. Some stick insects, indeed, dispense with males altogether, producing an endless line of females by parthogenesis.

This month's specimen, a mottled brown-grey creature 9 cm long, was promptly videoed, and news of its occurrence flashed to me by e-mail, together with a couple of pages on stick-insects swiftly downloaded from the Internet in case I should need them. In these high-tech manifestations, and my own subsequent browsing on the Web, I feel I have glimpsed the end of Nature Notes as they have long been known and loved.

How can I compete? Here for anyone to join is the Phasmid Study Group, based at Slough in England (http://www.ex.ac.uk/ gjlramel/psg.html), with 500 members in 23 countries. A mix of hobbyists and professional biologists, they keep 170 species of stick insect, meet twice a year in the Natural History Museum in London, and wear T-shirts "featuring either Heteropteryx dilatata, Aretaon asperimus or Oreophotes peruanus" in colour.

Judging by the Website photographs, no two species of stick insect have agreed on exactly what to look like (they are, after all, trying imitate the twigs and leaves of a wide variety of plants, in order not to get eaten). A general impression is of large, anorexic grasshoppers caught in the middle of their yoga exercises. In close-up, their heads have some of the charm of ET, and we are promised that stick-insects are "amazing, beautiful and generally easy to keep."

The Study Group offers exclusive species, unknown to your pet shop, and Care of Stick Insects comes at http://www.ex.ac.uk/bugclub/careshet/sticks.html. Ideally, it seems, a whole room should be kept at 75 to 80 C (I think they mean F.): otherwise it's little cages and light bulbs, with a red bulb at night when stick insects do their moving about and feeding (they stand around all day, motionless, which doesn't seem to offer very much to study).

There are people to meet, too. Somewhere in the US young Mark Watson, (http://members.aol.com/fluffymark/home.htm), gazes out through his granny glasses like the young John Lennon, wanting to enthuse about his pair of small spiny stick-insects Aretaon asperimus. There was also "A Mad American and His Buggles", but his home-page misfired and vanished overnight.

So this is one side of nature study on the Internet - the passionate amateurs, bonding for club-talk across the world. But interleaved with them, in the net's cross-fertilising anarchy, is an impressive amount of research posted by scientists. Stick-insects are ideal laboratory creatures, being long-lived, vegetarian and big enough to get hold of. They are perfect, in particular, for the study of how insects walk, a matter now hugely relevant to robotics, artificial intelligence, and the design of machines sent out to wander Mars.

Thus, mixed in with the hobbyclubs and home-pages, are papers on the energetics and mechanics of terrestrial locomotion, neural networks and interleg coupling, and other problems inherent in the "quasi-rhythmic movement of a six-legged, 18-joint walking system".

In The Task, for example, a paper posted by six American scientists at http://www.ee.cua.edu/bme-des/iv/hc/eiv-hc.htm, the stick-insect's walking is seen as providing "a particularly good behaviour for examining mechanisms for integrating autonomous activity with multimodal information from multiple sources including proprioceptors and exteroceptors" - namely, what they do next with each of six legs when proceeding across an uneven surface. Is this best decided by the rhythms of a central command system, or a control decentralised in the neural network? Read on, with furrowing brow.

No insect in the world has had quite this double life as domestic pet and behavioural laboratory model. But its abiding charm for children and adults is itself a paradox. A friend remembers buying a green stick insect in the Dublin Zoo pet shop some 30 years ago and keeping it "for ages" until the boy next door trod on it. What, I asked, was the fascination? He pondered. "It was invisible!"