Since 2008, we have continuously surveyed for the beetle from April to July each year, in order to monitor the population at Sherwood, producing short summaries of the records and detailing any findings. These can be found by scrolling further down this page, where there is a complete list of all known records from the Sherwood Forest NNR.

2011 turned out to be an exceptional year for numbers of adult Cryptocephalus coryli (more commonly known as the Hazel Pot Beetle) and by employing two unique survey techniques, we made several important discoveries regarding the habits of this endangered beetle.

The life cycle of Cryptocephalus beetles is an interesting one. Once mated, the female begins to lay, holding each egg laid between her rear tarsi, turning it and covering it with dung at the same time. Once the egg is completely coated, the female drops the 'pot' to the ground. When the egg hatches, the young larva makes a hole at one end, through which it can emerge to feed and move about in the leaf litter. As the larva grows, it enlarges the pot which eventually attains a length of about 14mm. In the wild, larval development usually takes two years, but larvae are often full grown within a year when kept in captivity. Once mature, the larva seals the end of the pot, turns around inside to face the other way and pupates. When the beetle emerges, it cuts itself out of the pot and climbs the nearest vegetation before flying.

Many years ago, Cryptocephalus coryli was a widespread species across the southern counties of England, but it declined greatly during the last century to become one of the UK's rarest insects. It's decline is thought to have coincided with the reduction in coppicing. Since 1970 it had been found at only three single sites - in Berkshire, Lincolnshire and Surrey (Ref: Natural England). In the south of the UK, it occurred on hazel growing along woodland edges, rides and hedgerows, but in the north preferred a heathland habitat with Birch scrub or young trees. Historically, Sherwood Forest was always regarded as being good for C. coryli by collectors in the early 1900's, when over a dozen adults could be taken on each visit to this locality, with the beetles either being beaten or picked from young Birch and Oak during June.

The re-organisation also provided additional records dating from 1929, 1939 and 1940, which seemed to have been previously unknown or were lost from the record books. These are listed in the table of all Sherwood's C. coryli records at the bottom of this page. Although most of these records still list no recorder or determiner, it is hoped that we can make further enquiries to complete the relevant information over the next few months.

In May 28th 2008, we found an attractive red beetle resting on a dead Rosebay Willowherb stem in an area of the Sherwood Forest Country Park. It's identity as a female Cryptocephalus coryli, was determined from photographs took on site, on our return home.

The area was surveyed on behalf of Natural England East Midlands by Allan and Annette Binding in 2009, whilst we continued our own searches for the beetle. Both the Bindings and ourselves, also conducted unproductive surveys at other potentially suitable locations within the Country Park area. We surveyed the area again in 2010 on behalf of Nottinghamshire County Council and in conjuction with our own survey work, finding only two adults, despite what seemed very favourable weather conditions.

Thinning work and the removal of timber was carried out as per our recommendations and damage to habitat by machinery was minimal at most. Birch and Hawthorn scrub known to be used by C. coryli females was left untouched. Trees in the remaining compartment not touched in March 2010, were later thinned in January 2011. We were personally involved with the work, selecting and marking the trees to be felled.

The whole operation went very well, with an increase in potentially suitable areas of habitat being created and opened up, but with just two adults recorded in 2010, it was always difficult to know if the beetle was in decline or it had just been a bad year. In the end, 2011 turned out to be a remarkable year with a total of 71 adults recorded.

Continued study and survey of the site during 2011 saw us greatly increase our personal understanding of the habits of C. coryli and several important new discoveries were made, which would certainly go some way towards explaining why coryli went 'missing' at Sherwood Forest (and probably other sites in the UK) for decades without being found.

Two adults observed on small scrub Oak and Birch and then seen flying directly to the top of nearby mature Birches, provided us with our first indication that we may have spent many hours looking in the wrong place (although still proving successful) and that maybe we were not looking high enough. We were able to confirm this during May and early June by advancing our survey techniques, conducting several surveys of the larger trees from the ground using binoculars and a telescope, all of which produced double figure counts during peak season. It was a slow and painstaking method involving several scans of each tree, but proved extremely successful on windless days. Finding that adults generally preferred taller trees, could be a likely expanation for the poor numbers recorded in 2010.

During windy weather, adult coryli adopt a policy of moving from the leaves and wrapping their legs around thin stems until conditions have settled. Even when on small scrub, adults are actually quite difficult to find when doing this. We were hampered by very breezy conditions on the day of the survey, but still recorded 13 adults which would not have been visible from the ground surveying with binoculars and telescope.

Over the years, the available literature has suggested that C. coryli uses 'key' trees, typically Birch scrub and young trees and whilst females are often found on Birches fitting that criteria, the number of adults found on these must be a fraction of the actual population.

Our reasoning for this stems from the fact that key trees have always been habitually small and much easier to check for coryli than much larger (30-50 feet high) trees. We believe that this has led to the misconception that key trees are used by successive generations of females. We are inclined to think that after spending many hours checking several key trees at Sherwood CP, we would have expected to have noted males flying around them or sat on them in their search for females. Several 'key' trees used in 2008 and 2009 have not been used since and it is most likely that many adults found on small scrub, have just simply climbed there after emergence, as they do grass and other vegetation before their first flight.

Plotting the locations of all adult coryli found at Sherwood Forest since 2008 on the map above, certainly shows that although this beetle is fussy about its habitat requirements, having the correct habitat for larval devlopment is even more important. The lack of habitat which combines the two required elements for both adult and larval stages, helps explain why coryli remains restricted at Sherwood Forest CP. Slightly damper soil containing a mixture of coarser grasses, Rosebay Willowherb and (to a lesser extent) Umbellifers, seems to be a key factor in larval development. Areas of finer grasses such as Fescues on drier soils are less suitable unless the grass is left untouched.

It was May 1st before the first female was found on a small Oak, but this was still another early date. She was photographed, but very quickly took flight and flew high up to the top of a nearby mature Birch. We made a return visit to the site in the late afternoon, to mark the locations of this year's two C. coryli, and found a third adult (a male) on a lower branch of a large Birch.

A technique employed by adults in windy conditions, came to light on May 8th. After scanning the upper reaches of Birches with binoculars and a scope revealed no adults, the reason for this was made clear by this female (shown left) found on a small scrub Birch, who was literally clinging on to the stem rather than the usual method of sitting directly on the leaf in fine conditions. Even with their red colouration, C. coryli are surprisingly difficult to see when adopting this position on small scrub Birch and Oak. By May 8th, the total number of adults found had reached 26, with the percentage of females being greater.

At the end of six hours, a total of 14 C.coryli had been located, which was a new record total, despite the windy conditions. All but one were at the very tops of mature Birches lining the southern edge of the favoured location, including one mating pair. With the wind being so gusty at times, all of the beetles were slightly down the Birch stems, clinging on tightly in the manner we noted the previous day when conditions were similar. A more thorough detailing of the days results can be found via the links at the bottom of this page.

The period May 11-17th continued to provide more records, with the total adults for the year eventually reaching 50 on the latter date. This period also brought with it slightly unsettled weather, cooler and frequently too windy to check the tops of Birches for adults, but also provided a string of records of recently hatched adults on either Willowherb or grass.

During the second half of May, conditions (although largely dry and sunny) were often windy, so it was not possible to survey the higher Birch foliage until early June. A few adults still kept turning up though, mostly on one clump of scrub Birch, but we also several found newly hatched adults on grass. On June 2nd, the weather was finally still, sunny and warm, so a couple of hours were spent scanning the tops of Birches with binoculars and a scope. A total of 15 adults were located (eight males and seven females) mostly very high up. Notable were two males and a female on the same leaf at the top of a Birch at the eastern end of the Gleadthorpe open, a grassy area within the country park.

There seemed to be a sudden end to the adult season, with just one solitary female with a damaged elytra, found in another new area on June 9th and remaining on the same scrub Birches until June 24th. Largely windy conditions continued, making scanning with binoculars and a telescope impossible, but also proving to be surprisingly fruitless when it was calm enough. A second tree top survey using the cherry picker was again conducted at the end of July and whilst we knew that finding any coryli was always doubtful, it was still worth the effort to check. A total of 71 adults were found during 2011.

The weather hampered searches for any very early adults and despite some fine sunny days there were overnight temperatures down to -3 during early May. As in 2009, all scrub Oaks were affected by frost, meaning that at least if any beetles were to emerge, then they would most likely be on grass, or on the limited amount of scrub Birch and Hawthorn (both unaffected by frost and in full leaf) available on site.

On May 16th, some three weeks after the start of our search, we found the first female on a small scrub Birch along a south-facing section of Birch woodland. This remained the only record until June 19th, when a male was found on young Oak growth on a stump cut down during the Winter.

The first adults (four) were found on May 10th, but casual searching actually commenced at the end of April. Hatching of the adults seemed to coincide with fine days, on which the temperature was fairly warm. Many adults were found on grass, including one female which was photographed egg-laying whilst on grass, both observations which had not been recorded before. Between May 10th and June 12th, we recorded a total of 13 adults of which four were males. These are listed at the bottom of this page. Further adults were recorded during a targeted survey by Allan and Annette Binding.

The number of adults found during 2009 indicates that Sherwood has a very healthy population of C. coryli and an appeal for more information by Allan and Annette Binding on the few other known UK sites for this beetle, saw no response. It appears that known sites in Lincolnshire have also proved negative for C. coryli.

Below:- Two C. coryli females, photographed at Sherwood Forest CP on June 8th 2009. The darker one of the two was actually found on June 4th and retained in captivity during a period of very wet weather. On release, we were fortunate to find this second female on a small Birch nearby.

There were a total of three records of C. coryli from Sherwood Forest in 2008. All three related to females, one of which spent several days on a small Birch and was photographed egg-laying on at least one occasion. The records and notes on their discovery are listed below.

Visual searches soon proved successful on a further two occasions, with another found a day after the first on 29/05/08 and a third, a few days later on 04/06/08. This female remained present till 07/06/08, never leaving her favoured Birch twig and was photographed in the process of egg-laying on at least one occasion.

The favoured Birch was just less than a metre tall, but just over a metre wide. Adjacent scrub was predominantly Oak of various sizes and a single small Hawthorn. Across the path there is an area of open, grassy heathland, in which there are several small areas of Birch scrub. These could be utilised as suitable sites for egg-laying females, but may be situated too far from the woodland edge.