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It is well known that Oak trees support more species than any other tree in northern Europe. It is also thought that the longer a type of tree has been populating an area then the more species will adapt to become dependant on it.

Hazel has been around a long time so I had a little mini safari poke about on the various hazel bushes in our garden. As you can see from the state of these leaves, they provide quite a lot of food for various species.

I found quite a few species, possibly the most spectacular was these Hazel saw fly larvae. (Croesus septentrionalis). They look like caterpillars but they turn into saw flies. They also have a curious defence mechanism, which is that if something disturbs them then they all arch backwards and present a jagged outline to the leaf. Presumably this is enough to deter predators.

Some of the species I found were incredibly small like a tiny spider and a red mite, here is a slide show of some of them.

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The largest I found was a stick insect, (Clonopsis gallicathis ) was about 10cm long.

I looked up on the internet (as you do) how many species live on Oaks and Hazel and found this article by T Southwood ….  is it the same Southwood who wrote the two volumes on British Moths back in the 1960’s ? …… probably.

So it is 284 insects on Oaks and only 73 on Hazel

Department of Zoology, Imperial College, London
It is common knowledge amongst ecologists and collectors that some trees have many species of insect denizen and others, usually recently introduced, comparatively few. But the number of species of insect associated with a certain tree would seem to reflect not only the actual time it has been present in Britain but also, and of rather more importance, its general abundance or scarcity throughout this period. If this hypothesis is correct, then in other parts of the world where the pattern of tree dominance is different from that in Britain, we should expect the comparative numbers of insect species to vary accord- ingly. The coniferous forest belt is far more extensive in Russia than in Britain and thus pine, spruce, larch and fir (the last three introduced species in Britain) will be comparatively
Table 1. Comparative series of the numbers of insect species on various deciduous (un- marked) and coniferous * forest trees in Britain and European Russia
Tree Britain Russia
Oak (Quercus) 284 150 Willow (Salix) 266 147 Birch (Betula) 229 101 Hawthorn (Crataegus) 149 59 Poplars (Populus) 97 122 Apple (Malus) 93 77 *Pine (Pinus) 91 190 Alder (Alnus) 90 63 Elm (Ulmus) 82 81 Hazel (Corylus) 73 26 Beech (Fagus) 64 79 Ash (Fraxinus) 41 41 *Spruce (Picea) 37 117 Lime (Tilia) 31 37 Hornbeam (Carpinus) 28 53 *Larch (Larix) 17 44 *Fir (Abies) 16 42 Holly (Ilex) 7 8