Cryptocephalus coryli

		Following on from our first, extremely successful and unique tree top survey for the Hazel Pot Beetle (Cryptocephalus coryli) earlier in May of this year, we were extremely fortunate to be able to conduct a second survey in the same area at the end of July. Though we knew 2011 to be an exceptionally early year for most invertebrates and that the survey date of July 30th would be a very late date by any standards for finding any C. coryli, the opportunity kindly offered to us by the late Bill Kew-Winder and Matt Vaughan of the former WKW Tree Services to conduct a second survey, was too good an opportunity for us to let pass by.
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Our survey took in all of the Birches on which adult beetles had been found during the May survey. Conditions on the morning were perfect for checking the tree top foliage for C. coryli, with warm temperatures and no wind. Leaf and tree movement was virtually nil, but despite this, the only beetles we found were single 7-spot and Harlequin Ladybirds. We checked all suitable Birch foliage, beginning our survey from the main coryli area and then working our way round the southern edge of the plantation, but still drawing a complete blank. It was pleasing to see that many of the oldest Birches had managed to produce better foliage, than was present earlier in the year, rendering most Birches in the area as being potentially suitable food sources for adult coryli. Oaks growing underneath the light shade produced by Birches, had also produced a flush of growth and showed little effects of the frosts of early May.
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Moving around the southern edge of the favoured plantation and after checking the Birches growing along the edge of this area, we made a cursory search of some of the tall Birches, growing well above the canopy of young Oaks in a plantation near the Gleadthorpe Open. The only beetle of note found during this part of the survey was the Chafer Hoplia philanthus, found at the top of a Birch.

This was an area in which we had found several adult C. coryli during the course of the Spring and early Summer and after the success of finding adults here (especially after predicting that this area was indeed potentially suitable habitat for them back in 2009) was very rewarding. Although very close to, and in the same general area as the bulk of records coming from Sherwood Forest since 2008, finding coryli in a new area was a significant find, showing that the colony is indeed doing well.

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That Cryptocephalus coryli is seemingly doing well here, does not mean to say that any protection given or offered to it should be lessened. This is still a beetle that needs help through considerate habitat management if it is to survive and although it successfully remained undetected at low population levels for 70 years, this should not be looked upon as being a reason to lessen any protection.

The Gleadthorpe Open area itself, is an amazing area of habitat. Quite untouched as long as people can remember and present as an open area for as long as any local maps show, this small section of grass heathland is probably unique in Nottinghamshire as an area of undisturbed habitat.

Notable for it's number of spiders, it is presently one of only two UK sites (both within the Sherwood NNR) for Zora sylvestris - a spider we often find where old heather grows over a well trodden footpath at the eastern end of the open. Quite amazing that this one area can hold two very rare inverts.

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The following four photographs show the Gleadthorpe Open from a height of around 50 feet. The area of heather and stands of mature Birch in the top two photographs show the habitat of both Zora sylvestris and Cryptocephalus coryli. Matt and myself conducted a brief search for Z. sylvestris, around the heather in this area, whilst Bill and Dilys surveyed Birches along the southern edge of the plantation for C. coryli. The mature Birches shown in these photographs were not surveyed on this occasion.

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Following a break for lunch, we moved to another area of the forest to search the upper foliage of some of the ancient Oaks. They are impressive from the ground, but from height, these spectacular, huge monsters show great fragility and structural weaknesses less noticable from the ground. It was good to have the chance to view them like this, after some years of looking up at them, but it does make you wonder how most of these trees have remained upright for so long.

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We found evidence that they have suffered from the consequences of a very dry Spring and Summer, usually in both leaf size and quaility, but the effect of the heavy snow the previous Winter, was plainly evident on some trees. Certainly the three trees we looked at were all typically hollow, more or less from top to bottom and these open cracks and crevices obviously support many invertebrates, most especially spiders, but the time of year meant that little was found on this occasion. We searched only by sight and by hand, but it may be worth beating foliage given the opportunity on another date in Spring. Another useful collecting option would perhaps be to take samples of the accumulation of dead wood and material from the hollows and old Jackdaw nests to search for Pseudoscorpions, spiders and other invertebrates.
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A number of Harvestmen found on both trunks and branches included the two common species Paraligolophus agrestis (above right) and Oligolophus tridens. We have found numbers of both these species on low vegetation over the years and it seemed very strange to find them 'out of context' but in general, very little was actually to be found within the canopy or on the main limbs.

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What was also surprising, was the lack of leaf mines of the common Phyllonorycter and Stigmella micromoths, all found easily from ground level. We had certainly expected leaf mines to be much more common at height than they actually were. A hopeful search for the mines of what would be a new species to Nottinghamshire (Phyllonorycter kuhlweiniella) proved negative on this occasion, but it was certainly worth looking for a species who's mines are usually found on the high branches of Oaks and rarely recorded.

One success we did have was using a pheremone lure to attract the day-flying Yellow-legged Clearwing (below). A total of 24 males were attracted and potted up in just over an hour, with another five males being missed.

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Our own previous experience when using the Yellow-legged Clearwing lure, has been of one or two moths an hour and with moths often being quite slow to appear, so our total was really quite exceptional. Dilys and Bill did most of the netting of these moths, with Bill developing an extremely good netting technique and dexterity by the end of the day.

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Despite the fact that we actually found very little during the day, this was still a very useful exercise and one which was once again, only made possible by the kind generosity of Bill and Matt from WKW Tree Services for generously giving their own free time, equipment and enthusiasm, to help us carry out this second tree top survey.

The fact that we failed to record any Cryptocephalus coryli, was due to the late date in what has been a very early season. This in itself provides us with some useful information and helps narrow the adults flight period down from what we had originally believed.

We both gained a great deal from Bill and Matt's willingness to answer our questions, freely sharing their expertise and knowledge gained through working with Sherwood's ancient Oaks. Hopefully they themselves learned something from us about Sherwoods range of invertebrates, although we think they already knew just what an exceptional place this is.

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A second tree top survey for the Hazel Pot Beetle July 2011

It was decided that the survey would target pretty much anything. If any coryli turned up, so much the better, but it was always felt to be extremely doubtful before the survey, so we later took the opportunity to have a look around several of the ancient Oaks, with no real idea of what might be found. Though we hoped for the leaf mines of Phyllonorycter kuhlweiniella, in the end we found very little, although even a negative result for C. coryli was actually informative, even if only narrowing down or confirming the adults expected flight period by it not being there.
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