| Hi Consuehlo, There are indeed several species of stinging tree, all belonging to the genus Dendrocnide, which contains about 70 species of which 4 are found in the warmer rainforests of Queensland and NSW. All seem to grow at the rainforest's edge and are species that characterise varying stages of regrowth. They are members of the family Urticace, the same family as the stinging nettles, and for some years the trees were called Tree Nettles (not to be confused with the nettle trees Celtis spp.). They operate by having leaves with 'hairs' made of hollow tubes of silica. These contain varying concentrations of formic acid (the same acid used by many stinging ants and wasps). When contact is made with the leaves the hairs penetrate skin and break off, delivering syringe-like injections of the acid. The pain caused varies from species to species. In general, the furrier the leaf the more stings and the worse effects of the venom. The least painful is the Shiny-leaved Stinging Tree D. photinophylla. Sometimes it appears not to have any effect at all. I believe there is still such a plant remaining as a street tree in the NSW town of Forster. Few people realisie what it is and so it has been allowed to stay there and is quite an attractive small tree. I mentioned this many years ago to a group of teenagers as I passed through the town. They found themselves drawn magnetically to the tree and couldn't stand not to try it out. Despite warnings they touched it, apparently to no effect. Soon half a dozen of them were wiping leaves over their arms and legs, showing how game they were. Remarking that it was all rubbish, they went off. Half an hour later the effects seem to kick in and they all complained of a an intensely annoying and rather painful, stinging itchiness like a sharp, irritating rash that took an hour or two to wear off. The largest and second most painful is the Giant Stinger D. excelsa, a buttressed rainforest giant growing to 40 metres (over 120 feet in imperial). It has leaves the size of dinner plates and is definitley not something to trifle with. Its sting is intensely painful and can endure for hours. In sensitive people it can last for much longer and recur on humid days when the hairs still remaining in the skin wash a little more poison in. I have often heard (hopefully) aprocryphal stories about this common tree such as the one about the female German entomologist who was collecting insects in North Queensland and needed to urinate. Still wearing her gloves she is said to have found a plentiful supply of large soft leaves from a nearby tree and used them as toilet paper. If she wasn't hospitalised afterwards she should have been for even thinking about it. The third and definitely nastiest is the spreading bush called the Gympie Gympie D. moroides. As the Giant Stinger is to the Shiny-leaved Stinger so it is in turn to the Giant. Its equally large, rounded leaves cause a far more intense, painful and persistent sting. I have heard of victims feeling the pain for months and that the pain can recur for many years when they shower or in humid conditions. Aprocryphal stories about this species include ones in which victims have been driven to suicide or died of shock from the pain. I knew a herpetologist who grew this species under the window sills of his reptile house to teach would-be burglars a lesson. These days he would be sued by stung burglars. Interestingly enough, the Giant Stinger, at least, produces edible purple fruits. I have in the past collected them (very carefully and with gloves and overalls) and stewed them into a really delicious brown jam/jelly with a subtle yet distinctively aromatic flavour. Thn tree produces a vaguely mulberry-like fruit even when it is young and short enough to reach the upper branches. If you see any of these plants in the wild they are invariable covered in insect chew marks and often the leaves are speckled with holes. Some of the smaller caterpillars seem to eat around the stings while others just seem plain immune. The Green Ringtail Possum of north Queensland eats the leaves, stings and all. It just goes to show that if you let evolution take its course for long enough there will be some creature that can survive anything. The reason the tree is the guardian of the rainforest is that it is most commonly found near the edge where "red gold", the Red Cedar Toona ciliaris, grows. This tree was so sought after for its beautiful timber that it is virtually extinct as a viable commercial timber species. To cut the Red Cedar you often had to avoid the stingers with their useless pulpy wood and vicious stings. Hope this answers your question. rodaf | 
