Recent records of the Harvestman Leiobunum sp. A from Nottinghamshire
Due to the number of years we have continued to survey the growing population of Leiobunum sp A on the walls of Worksop Priory and elsewhere, we felt that a separate (and more easily updatable) page giving the resulting counts on and observational notes was much needed.

A brief history of Leiobunum sp.A

In October 2009, we found a very dark, extremely long-legged Leiobunum type Harvestman on the wall of a Worksop house, which immediately stood out as being very different from any other Harvestman we had seen before.

The Harvestman was found resting on a shaded, north-facing wall, in the rear garden of the property, in a an open position relative to cover provided by Ivy growing up the same wall. It was collected and taken home for photographing before being released.

In November 2011, a possible breakthrough came whilst searching for images of Platybunus pinetorum, a recent addition to the UK species list discovered by Paul Richards at Sheffield in June 2010. Images found during a Google search for the similar looking (to the Worksop specimen) Leiobunum tisciae, turned up images of an invasive and unknown Leiobunum found in parts Germany, Switzerland, The Netherlands and Austria. Further research quickly led us to the excellent paper "An unidentified harvestman Leiobunum sp. alarmingly invading Europe" (Arachnida: Opiliones) by Hay Wijnhoven, Axel L. Schönhofer & Jochen Martens and published in December 2007.

One particular image of a male in the paper, seemed to match the Worksop specimen perfectly, so we emailed images of the Worksop specimen to Jochen Martens and Paul Richards for possible identification and confirmation. Both replied back with the conclusion that it was indeed Leiobunum sp. The Harvestmen still (February 2017) remains scientifically un-named.

Leiobunum sp.A refound - a summary of the 2012 records

Following the end of our three year wait to record Leiobunum sp. A again on October 13th 2012, we eventually went on to record a total of 13 males and nine females along the southern wall of the Priory. All the Leiobunum sp. A we found were found resting more or less at eye level, with only one female found about 20 feet up. They clearly preferred the vertical joints or tight recesses built along the southern side of the Priory walls. We made immediate follow-up visits the next day, recording a total of 20 individuals, before a final visit of the year on October 17th, recording a total of 18.

2013 records

Numbers increased on those initially found 2012, with counts of 37 on August 15th, rising to 43 on September 9th. Most of both these counts, were found in two aggregations, usually situated under some degree of shelter via the building's stonework, with up to 27 on the south side of the Priory and 11 under an arch on the eastern side. A count of 46 made on September 22nd, was the highest count to date.

Summary of the 2014 surveys and records 

We made two visits to the site and immediately found a single aggregation of 81 Leiobunum sp. A, a few minutes into our search on August 9th 2014.

The final total of 202, showed that there had been an enormous increase in numbers from 2013, possibly helped by the exceptionally mild Winter. Similar daytime roost sites, were used as in previous years, but we did note a substantial increase in numbers on the north (shaded) side of Worksop Priory.

Our second visit was made nearly a month later on September 7th and counts had increased to 274. There were increased numbers of Leiobunum sp. A recorded within all aggregations found on our first visit. The aggregation of 81 had grown to 95 and there were several other aggregations which totalled well over 30 individuals.

2015 surveys and records 

Our first visit of 2015 took place on August 2nd, which was a week earlier than in 2014. A total of 217 Leiobunum sp. A were counted, with many still immature, although there were already a few mature males present. Once again, the main aggregations were located in exactly the same positions on the Priory walls, as recorded in previous years. The largest single aggregation consisted of approximately 90 individuals, but higher than normal numbers were present on the eastern (recorded for the first time on the new section of the Priory) and the northern side. One immature male, was even found underneath the overhanging top stone of a grave and away from the main Priory walls.

Our second visit took place on August 15th. A total count of 212 was made, with groups in similar positions and there was an increase in the numbers of small groups. One usually guaranteed aggregation under an arch on the eastern-end of the Priory had disappeared.

  We returned to Worksop again on September 4th, noting changes to the distribution of Leiobunum sp. A on the north side of the Priory and actually finding very few to be present. Most were found on the warmer southern walls, probably moving as a result of the recent spell of cold northerly winds. A final total of 159 was disappointing, but a check of an adjacent stone building proved worthwhile, with a further 54 Leiobunum sp. A recorded. Final total for the visit was 213, so amazingly similar counts for all three visits this year so far.

On September 14th, we returned with wildlife cameraman James Dunbar to conduct another count. On arrival we immediately checked the first aggregation, which only a few weeks ago had held approximately 90 individuals. With the division of this aggregation noted on our previous visit, we noted a further reduction in numbers and after checking all the southern walls of the Priory, concluded that many Leiobunum sp. A had dispersed further afield, including one group which had aggregated on the north side of a large tomb.

No Leiobunum sp. A were found to be present on the Priory's eastern side and there were very few recorded along the northern side. Clearly there was a large reduction in numbers and possibly a more widespread dispersal away from the Priory. A total of 116 Leiobunum sp. A were found on the Priory and another 28 on an adjacent building, which had reduced in number from 54 on our previous visit.

On October 8th, we visited Worksop Priory to conduct another survey. Since our last visit, the weather had been largely fine and dry with some pleasantly warm daytime temperatures, but very cool nights. What remained of any of the aggregations present on September 14th, had dispersed and most of the 34 Leiobunum sp. A recorded were found well distributed over the walls of the Priory and with very few on the Priory's north side.

Our latest ever visit to Worksop Priory took place on November 1st. The day was pleasantly warm and sunny and a total of 31 Leiobunum sp. A (19m and 12f) were counted. There had been further movement/spread across the walls of the Priory, although none were present on the shaded north side. It was obvious that the remaining population had moved to the warmer southern and western walls and many Leiobunum sp. A were quite openly sat in full view. All were recorded singly or in twos, but not male with female. Most specimens had darkened further (especially the males) which we were surprised to find, now out-numbered females by almost two to one. Additional surveys for Leiobunum sp. A at other Worksop locations proved negative.

We continue to be convinced that there are other sites in Worksop for Leiobunum sp. A, but have had no success so far. The housing estate where we first recorded this Harvestman back in 2009, was also surveyed again in 2015.

Summary of the 2016 surveys and records

A much earlier visit was made to Worksop Priory, with the intention being to search for juvenile Leiobunum sp.A, which we thought would be low on the Priory walls by the middle of June. Our visit was on June 17th and we found most of the 85 Leiobunum sp. A as sub-adults, but we did record a few juveniles (shown right) of just 2.5mm body length.

There were no aggregations, but we did locate a loose group of eight sub-adults on the south wall of the Priory. None of the traditional aggregation areas on the Priory walls were occupied and most of the Leiobunum sp A found, were well scattered across the whole of the Priory's southern walls, usually in cracks and crevices, but often openly on the stonework in the manner of our native Leiobunum species.

Our second visit to Worksop Priory ended up being slightly later than we would have wished, but numbers had substantially increased and approximately 223 Leiobunum sp. A were counted on July 31st. Aggregations had again formed in the exact same locations on the walls of the Priory and on an adjacent stone building, as have been used in previous years. The largest single aggregation totalled 94 individuals.

Some two weeks into August and we visited Worksop again and found a record count of 308 Leibunum sp. A, on the Priory walls. The aggregation of 94 individuals on July 31st, had now risen to an impressive 130 by August 13th. This high count failed to increase (or even last) and by the time we conducted or next survey on September 10th, it was clear that the aggregations had broken up into considerably smaller groups. The largest group we found was just 24 and unusually, not in any of the traditional locations. A total of 146 Leibunum sp. A for the visit seemed small.

Fig 1: Below are our visit dates and counts of the Leiobunum sp A population at Worksop Priory since 2012. The small graph depicts the highest count per year, reading from 2012 on the left.

2012 2013 2014 2015 2016 2017
13/10/12 ....T22 15/08/13 ... T37 09/08/14 ... T202 02/08/15 ... T217 17/06/16 ... T85 05/07/17 ... T232
14/10/12 ... T20 24/08/13 ... T38 07/09/14 ... T274 15/08/15 ... T212 31/07/16 ... T223 28/07/17 ... T306
17/10/12 ... T18 07/09/13 ... T43 ... 06/09/15 ... T213 13/08/16 ... T308 ...
... 22/09/13 ... T46 ... 14/09/15 ... T144 10/09/16 ... T146 ...
... ... ... 08/10/15 ... T34 30/09/16 ... T63 ...
... ... ... 01/11/15 ... T31 16/10/16 ... T41 ...
... ... ... ... ... ...
Late Summer and early Autumn visits took place on September 30th, producing a total of 63 Leibunum sp A, and then on October 16th, when the count had lowered again to 41. Approximately 27 of the 41 total were males and the 14 females were mostly well scattered along the southern and northern walls of the Priory.

Summary of the 2017 surveys and records

We were slightly late conducting the first of the year's surveys, eventually visiting Worksop Priory a week later than we had originally planned to do.

Our first visit on July 5th 2017, produced a total of approximately 232 Leiobunum sp.A, with several specimens noted as having recently completed moults. We noted many more old skins on the walls, where other individuals had also recently completed the process. The count of 232 represented the third highest count we have had on the Priory. The largest percentage were counted on the south-facing walls and typically (for an early date) we found on the north walls and none at all at the Prioy's eastern end.

Leiobunum sp.A, looks set to be present in even higher numbers over the next few weeks, but we again found none on nearby buildings despite much searching.

We returned again on July 28th and almost bettered our record highest count of 308 Leiobunum sp.A recorded on August 13th 2016. We fell short by just two, counting 306 and with a single aggregation totalling approximately 100 individuals. Conditions were breezy, but we had many more on the northern walls of the Priory, than has ever been usual.
Summary of the 2018 surveys and records

Following the coldest Winter for a number of years, with some late snow, we wondered how Leiobunum sp.A had survived since our last visit of the previous year. Our first visit to Worksop Priory was on July 12th, during a period of prolonged, hot and dry weather. We counted approximately 170 individuals, of which quite a number were in the process of moulting. The distribution changes noticed last year were continuing and none were found on the eastern end of the Priory, but a good number were found on the northern walls. We presumed that the increase on the northern side, was due to Leiobunum sp.A avoiding the daytime heat.

Ten years on - the 2019 records

After a very mild Winter, where there were only isolated frosts and just the briefest flurry of snow one morning, our first visit to survey Leiobunum sp.A took place on July 7th. It was only a brief survey which saw an unexpectedly small total of 47 sub-adults and a few juveniles. They were located in the usual spots on the south and north walls, with the largest aggregation being of 28.

  Summary of the 2020 surveys and records

A first survey of 2020, took place on August 22nd. Only 58 Leiobunum sp.A. were found in three relatively small aggregation, the largest being of 28 rather restless individuals. This restlessness is thought to have been due to the very windy conditions over the previous few days, as this aggregation was rather exposed, but was in one of the usual (well used) locations on the south side of Worksop Priory.

It will be interesting to see whether there is a build up of numbers in the next few weeks, or if numbers here have declined.

A second visit took place on September 13th, after a large aggregation of Leiobunum sp.A. was found on Bridge Street in Worksop, by Ludwik Michalek the day before. This was the first report of any Leiobunum sp.A. away from Worksop Priory since the original finding back in October 2009 and confirmed our thoughts for a number of years, that it occurred at other sites. The aggregation were under an archway at the side of a cafe, close to the Bridge Street/Newcastle Street junction. From what I could see, the aggregation totalled 48 individuals.

A survey of Worksop Priory's walls produced a count of 52  Leiobunum sp.A. so it does seem as though there has been a decline in numbers on the Priory, probably due to a localised expansion of range.

A further visit on October 14th produced 23 Leiobunum sp.A. scattered in a group of nine and then mostly in one's and two's around the walls of the Priory. I returned to Worksop a few days later on October 18th, this time to check on the Bridge Street aggregation. A total of 13 were found, most still located in the archway next to the cafe, with a few singles found a few buildings away, but aggregations at both the Priory and Bridge Street are obviously splitting up now.

2021 records of Leiobunum sp.A

A rather worrying first survey of the year on June 24th, with the finding of just a single sub-adult Leiobunum sp.A. located during a thorough survey of the Priory walls. It was in one of the regular aggregation locations, but worryingly all the other regular aggregation sites along the Priory walls remained vacant.

Concerns remaining from the year's first survey of June 24th, were lessened by the time I'd counted approximately 50 individuals on a survey conducted on July 12th. There were no large aggregations, but some definite signs of grouping had developed since the last visit, although no group totalled more than six. Around ten individuals had already reached the moult prior to attaining maturity and still maintained the characteristic (but reduced) white knees typical of sub-adults. The age range of all Leiobunum sp.A found was interestingly varied - ranging from small juveniles, through sub-adults of varying size ranges, to those prior to becoming adult. Such variation in growth hasn't been recorded here before, when growth within the population has always been generally close.

The Priory was next visited on August 6th and it was hoped that there would have been an increase in numbers. It turned out that there hadn't and 48 were found (all at the same stage of development now) but still a moult away from adult. The weather on the day was very showery and breezy, which are not the best of conditions, so maybe more were well tucked away and sheltering from the worst of the conditions. However, a month later proved that maybe some dispersal has taken place and numbers on a survey on September 9th were worse, with just 19 found. All were adults and of the 19, just four females were out-numbered by 15 males. Clearly something has occurred, or is occurring with this population. Possibly, colder weather the previous Winter may have had an affect on numbers here, or it could be that after years of establishment, the population is now spreading away from the walls of Worksop Priory. There's still so much to find out. 

I made a visit to Worksop B&Q on 11/10/21 and discovered 11 adult Leiobunum sp.A. on the outside walls of the garden centre area. Further searches saw a female present on the outside wall of B&Q near the main entrance and the record confirmed that there was the expected spread to new sites. To end the year's surveys, I made a quick visit to Worksop Priory on 27/12/21 and was surprised to find a single female on the southern wall of the Priory. This was the first December/Winter record of Leiobunum sp.A. in Nottinghamshire and with very mild temperatures forecasted into the new year, she should have survived into January. 
2022 records

A very promising start to the survey season on July 13th, especially in view of the poor numbers of the previous year. A total of 104 Leiobunum sp.A were found in various stages of growth, although there were no notably large aggregations were present, with the largest aggregation containing approximately 26 individuals. However, on subsequent visits, rather than he expected increase in numbers of Leiobunum sp.A, there was an unexpected drop in numbers, with counts of 36 on 05/08/22 and then just 15 on 17/08/22.

The only possible explanation and cause, could be that the low counts were a direct result of a second period of very hot, dry weather experienced before these latter two surveys? Another visit to the site on 31/08/22, again saw another count of just 36 individuals. But an interesting observation over the last three visits, was that all three counts were of single aggregations. No other individuals were recorded elsewhere on the Priory walls, or located on previously used adjacent walls. But it was not all bad news, with Leiobunum sp.A again recorded from the garden centre walls of B&Q on Sandy Lane, where two aggregations (one high on the shop frontage) totalled 25 on 05/08/22, but had risen to 71 in two aggregations on 31/08/22.
By the time of the next visit to Worksop on September 27th, just four (2♂ and 2 ♀) were favouring the same location on the Priory wall, as the aggregation had done all year. No others were found during a thorough search of the Priory and in the immediate area, but I did go and check the site on Bridge Street where Leiobunum sp.A was found in 2020 and was pleased to see that around 30 were present in a tight aggregation. The following day, I visited the B&Q store on Sandy Lane and found that counts had dropped, but there were still 21 present on the garden centre department's exterior wall.

But more exciting news was to come in early October, when a single Leiobunum sp.A was found on the Nottingham Trent University's Arkwright Building on Shakespeare Street in the centre of Nottingham. Found by Oli Harrison on October 7th, this record surely has to be just one of numerous sites within the City and a great find. 
Fig 2: Below is an updated version of the table showed in Fig 1. It shows the dates visited and the corresponding counts of Leiobunum sp.A at Worksop Priory between 2012 and the very latest counts from 2023. ' T ' is the total recorded.
2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023
13/10/12 .T22 15/08/13  T37 09/08/14  T202 02/08/15  T217 17/06/16 .T85 05/07/17  T232 12/07/18 .T170 07/07/19 .T47 14/10/20 .T23 24/06/21 .T1 13/07/22 .T104 12/07/23 .T49
14/10/12 .T20 24/08/13 .T38 07/09/14 .T274 15/08/15 .T212 31/07/16 .T223 28/07/17 .T306 .. .. .. 12/07/21 .T50 05/08/22 .T36 14/08/23 .T125
17/10/12 .T18 07/09/13 .T43 ..... 06/09/15 .T213 13/08/16 .T308 ..... .. .. .. 06/08/21 .T48 17/08/22 .T15 11/09/23 .T58
... 22/09/13 .T46 ... 14/09/15 .T144 10/09/16 .T146 ..... .. .. .. 09/09/21 .T19 31/08/22 .T36 10/10/23 .T4
..... ....... ..... 08/10/15 .T34 30/09/16 .T63 ..... .. .. .. 12/07/21 .T28 27/09/22 .T4 10/12/23 .T1
... ... ... 01/11/15 .T31 16/10/16 .T41 ... .. .. .. .. .. ..
... ... ... ... ... ... .. .. .. .. .. ..
2023 records of Leiobunum sp.A

The first visit to Worksop Priory on July 13th 2023, provided just two aggregations of Leiobunum sp.A from the walls of the Priory. A total of 49 Leiobunum sp.A were counted, with the largest of the two aggregations being made up of 39 individuals.

There was better news in the way of success when approximately 70 were found on the walls of Nottingham Trent University buildings on Bilbie Walk, between Goldsmith Street and Shakespeare Street, with three aggregations forming part of the final count on July 23rd 2023. This site was discovered in late 2022 by Oli Harrison.
  The folllowing day, I visited B&Q on Sandy Lane in Worksop on July 24th and there were several aggregations on the exterior wall of the garden centre section, plus an additional small group on the front of the building. A total of 60 Leiobunum sp.A were counted, with the largest aggregations including 18 and 22 individuals.

Back at Worksop Priory and a count recorded on August 14th had increased sharply to 125 Leiobunum sp.A. This was up from the 49 present a month earlier on July 13th. There were three aggregations of 62, 24 and 22 individuals recorded and two smaller groups and odd singles also found. None were fully mature. 125 represented the highest Priory count since 2018 and while still a good count by the standards set in recent years, it is still less than half the 308 and 306 counts seen in 2016 and 2017 respectively.

A visit on September 11th proved disappointing and just 58 Leiobunum sp.A were located, with just two aggregations of 25 and 20 individuals. It was noted that all individuals seemed to have moulted to maturity, since the last visit a month before. This visit did follow a week of very hot weather, which may have caused some movement to inaccessible areas of the Priory walls to escape the heat, or may just be natural dispersal now mature?
October's Worksop Priory visit came on the 18th and a small number of Leiobunum sp.A, were recorded within a small area of the southern walls of the Priory. The count consisted of two males and two females, all in the favoured area where most of September's count was made. A late in the year visit on December 10th, saw a single female still present in the usual section of Priory wall, which had surprisingly survived the snowfall and series of very hard frosts with associated sub-zero temperatures.
The discovery of Leiobunum sp. A at Worksop in 2009