Houses in the hazel

img_5670When camping up at the wood this summer, Mark was the first to notice there was something odd going on in the hazel. Little folded leaf lanterns had begun to appear in the branches near the tent, as if some strange little imp had developed a passion for origami. Now hazel (Corylus avellana) has long held a reputation as a magical tree. Its branches are used to divine water and were considered to protect against spirits. In the mediaeval times the tree was a symbol of fertility; in Ireland, it was known as the tree of knowledge. Carrying a hazelnut was thought to ward off rheumatism or act as a charm. But nowhere could I find a reference to it being a source of fairy lanterns. The shrubby growth of hazel provides shelter for birds, and the nuts are eaten by woodpeckers, nuthatches and small mammals including dormice, but it doesn’t appear to be cited anywhere as providing a home or food source for origami-minded fay. So what on earth was hanging these miniature packets on the springy hazel poles?

It took me a while to get to the bottom of the mystery. My usual books did not cover our mysterious visitor, nor the websites I usually find informative. In the end, after a bit of delving around, I discovered a journal article entitled ‘A Biologically Little Known Species of the Attelabidae (Coleoptera)’ by Jaroslav Urban¹ which finally shed light on our decorated hazel trees. It turns out that these parcels are made by a beetle, which may or may not be a weevil (that argument seems to be still running, but I am tending towards the identification weevil beetle); it is the hazel leaf-roller (Apoderus coryli) to be precise. It is a lovely beetle according to its photographs – squarish, beautiful red back, with a black head which becomes very thin behind making an elegant neck. But I have not laid eyes on this beetle – all the work it has done in the wood, it has done in secret. What I am seeing is the evidence of its fascinating life cycle.

The hazel leaf-roller is at the northerly edge of its range here in the wood, and if I want to catch sight of it, I will need to be looking in the months of May to July (I have already made a note in my diary). It’s then that the beetles emerge from their hidey-holes where they’ve over-wintered to feed (on the newly opened hazel leaves) and mate. Then comes the fun bit. Once the female is ready to lay her eggs, she chooses a suitable hazel leaf and cuts her way through the top of it, a little way down from the stem; she starts on one side, cuts through the leaf to the main stem, through the main stem, but stops before she cuts through the whole of the other side of the leaf, leaving a few of the lateral veins remaining to hold the leaf in the tree. (I have been trying to think of another way to describe this – it’s a bit gruesome, but it’s like cutting off your hand finger-side of your wrist, but leaving the bones of the little finger intact to prevent your hand from actually falling off.) The beetle then pops off for a short break while the section of the leaf, no longer supplied with water because of the damage to the veins, begins to wilt.

Once the leaf is wilted and soft enough, the female beetle will lay usually one egg, but sometimes more, at the tip of the leaf (the number of eggs laid seems to depend on the size of the leaf). And then, this amazing beetle begins to roll up the leaf into a tight tube, closing off both ends with folds so that eventually there is a cylinder with five to ten layers of leaf, making a stable environment and the perfect little home for this beetle’s offspring to grow up inside. The eggs hatch into larvae which eat the withering, withered and decaying leaf tissue rolled up in the interior of the rolls, while the leaf tissue still connected to the lateral veins remains green, surrounding the cylinder and holding it in the tree. The larvae even pupate in their house, to emerge as beetles when they become adults. These new beetles could go on to have another generation if the conditions were really good, but otherwise, they will head off to overwinter, ready to demonstrate their own amazing leaf folding skills the following year…

So, the sceptic in me is silenced – those little lanterns we found in the hazels really are magical; I’d find it hard to think of a more fantastic explanation for these intricate structures than a beetle-built, origami nursery for a young hazel leaf-roller.


¹Urban, J. (2014) ‘Apoderus coryli (L.) – a Biologically Little Known Species of the Attelabidae (Coleoptera)’, Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis. Mendel University Press, 62(5), pp. 1141–1160. doi: 10.11118/actaun201462051141.

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