European records of Leiobunum sp

The first records of a large, dark Leiobunum sp Harvestman came from near Nijmegen, The Netherlands in October 2004. Experts using Martens 1978 key, could not identify it as being any north-western or central European species, nor were they able to assign it to any European representative of the genus known to date. Many more additional records were obtained from several localities near to Nijmegen during 2005 and 2006. First records from other European countries are Germany and Austria (2006) Switzerland (2007) and from France in 2009.

Background history of the Worksop record

Recording and photographing invertebrates, occasionally throws up something obviously very different from what you have seen before, but still remains unidentified despite a great deal of research. The result is that the images get put into the 'unidentified folder' and often sit there for months or even years. Images of this Leiobunum type Harvestman taken at Worksop in October 2009 did exactly that. Yet the inability to ID it, probably niggled us more than any other species and the 'unidentified folder' was subsequently opened several times in the intervening period.

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 sp 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. There is a link to this paper at the bottom of this page. 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 this is indeed Leiobunum sp.

Jochen replied "Certainly, it is the Leiobunum species presently extending it range within central and now even to NW Europe. Very amazing that it reached the British Isles with so short delay. I understand that only this male was present. This is unusual because in most cases the local population enlarge quite rapidly and form the mass aggregation of which you certainly have seen photographs. But, locally, this may be only the beginning. So, please, keep an eye on the further development and ask around. According to my knowledge, this is the first record in the U.K. Many thanks for informing me (and hopefully so on further records to come)".

The specimen was found on the wall of a Worksop house on the Prospect estate at approximately SK 59226 80970. This is situated off Gloucester Road, immediately north from Bassetlaw Hospital. The house is situated in a row of terraced town houses built in the 1970's, with small gardens facing east at the front and west at the back. Both gardens are enclosed, well planted with mature shrubs and conifers and sheltered by fencing. It is a typically designed estate of it's time - a maze of paths and cut grass areas etc. Houses are arranged in short rows facing different directions.

Despite being part of an urban estate, this small garden has supplied us with numerous interesting invertebrate records, with a healthy list of Harvestmen including Odiellus spinosus, Oligolophus tridens, Opilio canestrinii, Opilio parietinus and Paroligolophus agrestis. Surprisingly, we never recorded either Leiobunum rotundum or L. blackwalli, two common, long-legged Harvestmen.

A very large male Leiobunum sp. Size difference from Leiobunum rotundum and L. blackwalli extremely obvious at a glance. Maximum leg span of the Worksop specimen measured at 100.0mm, compared to an average sized male Leiobunum rotundum of 66.0mm. Body length 5.0mm