Summaries and records of Cryptocephalus coryli at Sherwood Forest

Documenting one of Sherwood Forest's rarest beetles, this page lists all the Cryptocephalus coryli records known to us. Regular visitors to this site will know how much work and study we have put into recording this beetle and continue to do so. Survey work from 2009-2012 has shown that the coryli population at Sherwood Forest is more substantial than earlier surveying had originally implied, although despite being recorded in increasing numbers, it continues to be found at just one small location within the Sherwood Forest Country Park. Many years ago, Cryptocephalus coryli (commonly called the Hazel Pot Beetle) was a widespread species across the southern counties of England. But it declined enormously during the last century to become one of the UK's rarest insects. Its decline may have coincided with the reduction in coppicing, but climatic changes may have been equally likely.
.......................
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. In recent years, it was believed that the Sherwood Forest colony was the only one left in the UK and since 1970, it had only been found at three single sites - in Berkshire, Lincolnshire and Surrey (Ref: Natural England) and was believed to be extinct from all other known sites. No recent records were forthcoming following enquiries by several authors of recent reports on the beetle. In July 2013, Allan and Annette Binding reported that Allan recorded a single male Cryptocephalus coryli at a heathland site in Clumber Park earlier in July. This is obviously a new Nottinghamshire site for the beetle, so is welcome news indeed. Allan and Annette also reported that two females had also been found at Whisby in Lincolnshire by Richard Davidson. Whisby was the location of a release scheme a number of years ago and it was thought that the beetle had died out there until Richard' discovery. We know that it is currently doing well at Sherwood Forest, but it is strongly believed that C. coryli is still present at Box Hill and Headley Warren in Surrey (per Denton, J. and Collins, G.) but no one has purposely looked for it in the last few years. There have also been no records from Woolmer Forest in Hampshire, since it was recorded there for the first time in 2002 (Lawn, M.) despite further searching and there have been no records from any Lincolnshire site other than Whisby since 2007 (per Barnes, C.). Searching the tops of Birches at any known or former coryli site, will probably reveal that the beetle is still present.
.......................

		Most recent Cryptocephalus coryli records 2014-2021 After 2013, we made only occasional visits to that area of Sherwood Forest CP traditionally favoured by Cryptocephalus coryli. With no encouragement or interest showed by site management in even having the presence of such a rare beetle on site, their lack of enthusiasm eventually rubbed off on ourselves and we were just happy to record it for that year, then record elsewhere. We did record three males and a female on 03/05/14, which were found on either scrub Birch or the lower branches of more mature Birches. Despite a number of visits in 2015, we failed to find any coryli, but were pleased to record three (two males and a female) on 28/05/16, with two 25 feet off the ground on Birch. Records in 2017 produced two females on 11/05/17, another female on 23/05/17 and then a male and female 25/05/17. Since then, it's just been single adults on single dates annually, with a female on  23/05/18, a male on 16/05/19, another male on 01/06/20 and a female on 23/05/21. Records in 2022 look to be restricted to the upper reaches of Birches, following the cutting of all Birch scrub in the area in late 2021.
.......................

Summary of C. coryli records from Sherwood Forest NNR in 2013 We did less work on the number of C. coryli at Sherwood Forest this year, due largely to the general lack of interest in the beetle's presence or status, shown by any of the NNR's management team. Numbers do appear to be stable and coryli did seem to have a good year. A total of ten adults were recorded between 19/05/13 and 30/07/13, with a maximum count of four on 22/05/13. Most of the records came from either Hawthorn or Birch scrub. No tree top surveys using binoculars or telescope were carried out this year.
.......................
Summary of C. coryli records from Sherwood Forest NNR in 2012 There was a slightly later start to the 2012 season than in the previous two years, with the first female found recently emerged on coarse grass, during a short afternoon site survey on 17/05/12. 2012 proved to be an interesting year for this Sherwood speciality, with a further small increase in site range, but it was not all good news. Site management in the area of the Country Park favoured by coryli, at times remains an issue and late in 2012, a work party effectively removed all the Birch and Oak scrub (shown below) from an area used by coryli to allow heather/heathland regeneration. It was disappointing to us as recorders, that a small area of habitat be given precedence over the possible requirements of an endangered (RDB1) species and it was not the fault of the work party. Despite our growing leaning towards coryli not being totally dependant on Birch scrub (as had been believed) females certainly do use scrub at times, although we don't know yet whether this is accidental or quite deliberate. Despite many hours in the field, we have also been unable to ascertain whether they actively seek out and use Birch scrub from a certain point in the Spring.
.......................
It could be that mature Birch leaves lose some of their nutritional value as a food source and that the adults (in particular females) then seek out Birch scrub. Trouble is, it will be difficult for us to determine now. An exciting discovery was made on 20/05/12, when Ranger Gary Joynt found a female at the base of a Birch trunk, effectively changing our knowledge of Cryptocephalus coryli at Sherwood Forest. The importance of the find was that this beetle was discovered for the first time within closed canopy woodland, around 50-60 metres away from the woodland edge where the beetle regularly occurs. The location of this newly emerged female amazed us, meaning that coryli must also be found on Birches situated quite deep within areas of woodland and that they are not completely confined to warm south-facing trees or woodland edges. Taller Birches standing slightly above adjacent trees must also be capable of attracting females, possibly due to their prominent position above the tree canopy.
.......................
A total of 40 adult coryli were recorded between 17/05/12 and 18/06/12, with a ratio of 19 females to 21 males. The figures for 2011 were 71 adults (42 females to 29 males). Two surveys using optics were conducted on favourable days, with a total of 12 adults, including eight males and four females found on 23/05/12, including one pair observed in cop. All adults were located near the top of Birches growing along the woodland edge, typically favouring trees in the 25-35 feet range and with healthy foliage. The next morning saw an early binocular/telescope survey start of 7am, but no adults were located until around 08:45h when they became active, despite the warm, sunny conditions. The survey concentrated on trying to further establish the range of coryli on site, rather than go for numbers. This was successful, with two females located at the very tops of two Birches, at around 30 feet height and situated in suitable habitat. They were in an area that we have consistantly searched for them in since 2009, always feeling that it would produce records, but much sooner than the four years it has taken. However, the downside to this good news, was that two of the compartment boundaries had been changed earlier in the year and that the trees the beetles were located on, were now in a grazed enclosure! While the adults can utilise these trees in future years, it means that any resulting larvae they produce, are unlikely to ever make the change to adult, due to trampling by Longhorn Cattle and their grazing of the grass.

.......................
		BINDING, A.E., BINDING, A., PENDLETON, T., PENDLETON, D. & CLIFTON, S.J. 2011. The status of the hazel pot beetle Cryptocephalus coryli at Sherwood Forest National Nature Reserve. Natural England Commissioned Reports, Number 066. Published 23rd February 2011 Left is a link to the Natural England commissioned report from 2011, in which Dilys and I were down as co-authors, following our involvement with the surveys of Allan and Annette Binding back in 2009. The disappointing aspect, which still niggles to this very day, is the obvious lack of notice taken by site management, whether it be Natural England, Nottinghamshire County Council or the RSPB, in their complete disregard towards recommendations contained within the report, for maintaining habitat suitable for Cryptocephalus coryli. It hardly does much for encouragement and you have to wonder what the point is of any report, if recommendations are ignored.

Summary of C. coryli records from Sherwood Forest NNR in 2011
.......................
Following on from a poor year for C. coryli numbers, coupled with an exceptionally cold period at the end of 2010, it was always going to be a guess as to what would happen in 2011. Certainly the weather during the early months of this year was especially favourable, with the remainder of the Winter and early Spring being very dry. April's dry and at times very warm weather, saw many invertebrates produce early first dates and the first adult coryli (a male) was found on the exceptionally early date of April 23rd. This was certainly the earliest record for Sherwood Forest and very early nationally, with mid-May to early June generally being regarded as the main emergence period for adults. 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.
.......................

May 2nd saw a further two females found on a small Oak (which soon flew off unseen) and a large Birch respectively and within a few feet of each other. Scanning the lower branches of large Birches growing along the southern edge of the favoured area with binoculars on May 3rd, revealed another male and two females, bringing the total of adults for the year to eight.
.......................
May 4th was a significant day, when a concerted effort was made to check the higher branches of the mature Birches along the edge of the favoured plantation. Binoculars and a Kowa telescope were used to find and sex any adults, resulting in a staggering total of 11 adults including six females and five males. One Birch alone produced three males in close proximity to each other. Perhaps a more important discovery, was a male and female found in a new location, slightly away from the known population. This new location provided additional records of females found on May 6th and then recently hatched on May 10th. 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.
.......................
		On May 9th we were able to conduct the first of two unique surveys with the very kind help and support of WKW Tree Services. The surveys were based at tree top height, using a cherry picker operated for us by the extremely willing Matt Vaughan. 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.

Summary of C. coryli records from Sherwood Forest NNR in 2010
.......................
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. Despite having the coldest Winter for many years, we began actively searching for the first C. coryli from around the start of the last week of April 2010. 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. Summary of C. records from Sherwood Forest NNR in 2009
.....
		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. Adults were found over a larger area than in 2008, but still in a restricted section of Sherwood Forest CP. Records throughout the Spring indicated that this beetle is largely found along the southern and eastern edges of one section of Birch and Oak woodland within Sherwood Forest CP, with adults generally being noted on grass (providing most records) or on Hawthorn and Birch scrub.
.....

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. Summary of C. records from Sherwood Forest NNR in 2008 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.
.......................
Following the discovery and identification confirmation of the first female on 28/05/08, further visual searches of Birch/Oak scrub foliage in other nearby compartments were made. These took place on an occasional basis until late June. 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.
.......................
It is possible that the Oak scrub were ignored by the females, due to being severely frost damaged after leaf emergence. By the time the Oaks had recovered, the C. coryli emergence/breeding period was over. The Birch also held numbers of Sloe Bug (Dolycoris baccarum) and the ant (Formica fusca). No prolonged observations were made at the time to determine whether these two insect species had any adverse effects on the female coryli presence, but any effects must have been minimal given the female's lengthy duration of stay.
.......................

Cryptocephalus coryli (main page)

Tree top survey for the Hazel Pot Beetle - May 2011

Tree top survey for Hazel Pot Beetle - July 2011

Rearing Cryptocephalus beetles in captivity

Beetles

Insects

Homepage

Contents