Ocularium

Newsletter of the Opiliones Recording Scheme
(New Series)

Editor: Paul Hillyard
c/o The Natural History Museum
Cromwell Road, London SW7 5BD Tel: 0207 942 5127 Email:
pdh@nhm.ac.uk

No. 3

November 2000


Editorial

Editorial This issue of Ocularium is mostly devoted to a report of the discovery of a species of harvestman new to Britain. This news dominates the issue because such discoveries are, of course, rare and newsworthy events. But it also dominates because of the shortage of other contributions. So, once again, the editor cries (literally): please do try to contribute some news, short articles or observations of your own - anything at all - for the next issue. Either that, or someone will have to discover another new species! Go for it!

Opilio canestrinii (Thorell, 1876)
- NEW SPECIES RECORD for BRITAIN

Peter Harvey submitted a specimen last year (just as Ocularium was going to press), which he had collected at Banbury Reservoir, Lea Valley, Essex (TQ358911) on the 28th of October 1999. This male specimen is immediately recognisable as being close to Opilio parietinus but is readily distinguished from that species by the contrast between the pale body and the dark legs. The contrast is striking because the legs' basal segments (coxae and trochanters) are pale-coloured, like the body, but the other leg segments from the femora outwards are dark brown.

Peter reported: "The harvestman was collected from a metal fence by the side of a footpath with a reservoir on one side and grassland on the other side. There was a strip of tall herbage running along the fence. There were also lots of juvenile Theridion pictum specimens, a spider common in Essex only along the Lea Valley and always close to water."

Opilio canestrinii has been steadily moving north from its original range (Italy, Austria, Switzerland and Germany) for some years now. In fact its arrival here was predicted by John Sankey as early as 1986.

Dr Henrik Enghoff (Zoologisk Mus., Copenhagen) wrote (1987) about its discovery in Denmark: "Opilio canestrinii is recorded for the first time from Denmark, based on numerous finds on house walls and similar habitats in Jutland and the islands of Zealand and Bornholm in 1986. The species is probably a new immigrant in Denmark, since an extensive survey during the years up to 1962 failed to reveal it. "

Dr Jochen Martens (J.Gutenberg Univ., Mainz) wrote on hearing the news of the find in Britain: "As to the biology of O. canestrinii I want to draw your attention to an interesting fact: Alongside the colonisation of Central Europe by canestrinii, the two common other Opilio species, parietinus and saxatilis, nearly disappeared. This may happen also in the UK and all fellow arachnologists should help in a survey of the actual and later distribution of both species in the UK, then watch what is going on within the next years when canestrinii will become more common in your country."

Dr Jurgen Gruber (Naturhistorisches Museum, Wien) offered some thoughts (pers. comm.) on the means by which the harvestman may have expanded its range: "I have seen a couple of the same species from the central region of Upper Austria. I guess that spreading over short distances occurs by walking as usual - and over longer distances by human-asssisted jumps (eggs in soil?....). Another guess is that it is primarily a planticole species; in its secondary range it is predominantly synanthropic and found on buildings and walls - though there are a number of records from vegetation, generally not far away from settled areas. Of course, there may be some collecting bias here."

In the monograph by Martens (1978) the name Opilio canestrinii (Thorell, 1876) does not appear. However, Martens lists, under Opilio ravennae Spoek 1962, a number of names which, together with the name O. ravennae, are considered by Gruber (1984), to be synonyms of one of two species: Opilio canestrinii (Thorell, 1876) and Opilio transversalis Roewer, 1956.

O.canestrinii differs from our two resident species of Opilio by the two well-marked carinal lines on the shaft of the male organ (right).

The editor is informed that there are other records of O. canestrinii in northern Europe: Bliss, 1990 (Sweden) and van der Weele, 1993 (Netherlands). Sorry but further details are not known.

References:

Enghoff, H. (1987) Opilio canestrinii (Thorell, 1876) - a newly immigrated Danish harvestman (Opiliones). Ent.Meddr. 55: 39-42.

Gruber, J. (1984) Uber Opilio canestrinii (Thorell) und Opilio transversalis Roewer (Arachnida: Opiliones, Phalangiidae). Ann. Naturhist. Mus. Wien 86 (B): 251-273.

Martens, J. (1978) Weberknechte, Opiliones. Die Tierwelt Deutschlands 64: 464 pp.

Dicranopalpus ramosus

New finds of Dicranopalpus ramosus continue to be reported. According to Mike Davidson, the harvestmen has been found in a garden in Edinburgh but the details are as yet unknown and it is not possible to confirm yet that this is the most northerly record in Britain. Wayne Rixom says that it is now very widely distributed in the Midlands and he adds that it is easy to identify! A.E.Cooper reports that it is popping up regularly in Somerset - in 1995 at Hinkley Point Nature Reserve a search did not find it but later, in 1999, numbers of specimens were found there. Furthermore, Richard Gallon has found it at a number of sites in North Wales.

NOTES ON HARVESTMEN in DORSET

John Hunnisett has contributed the following:

A. cambridgei seems to eventually turn up in most areas where I have put pitfall traps down for long periods, therefore I think it could end up as being a common species.

I can't decide whether M. chrysomelas is genuinely only local or that it is just difficult to find. It has occurred in most type of habitat.

In many locations D. ramosus is the most common species, one sometimes gets the impression at the expense of others such as L. rotundum.

I think both L. palpinalis and L. ephippiatus will end up as being scarce as I have only found them in leaf litter and pitfall traps. I tend to collect a lot of leaf litter!

All records of O. parientinus and O. spinosus are from urban areas which are often not easy to survey, so the distribution is probably not representative.

R. triangularis is under-recorded, being a species of late spring I haven't woken up to the fact that I should be looking for it.

N. gothica is I think genuinely scarce.

MASS AGGREGATIONS of harvestmen

In response to the item in the last issue, Richard Gallon has reported an interesting sighting at Rostherne Mere (SJ743838): "I happened to examine the shaded westerly facing wall of the boat house. On this wall, I found a large, loose aggregation of approximately 400 adult Leiobunum rotundum covering an area of about two square metres. Both male and female specimens were present. I was collecting data at fortnightly intervals and was able to confirm that the aggregation persisted between 5th June and 2nd July 1998."

RECORD CARDS SUBMITTED

Many thanks to the following recorders for submitting records last year: A.E. Cooper, M.Davidson, R.Gallon, J.E.Milner, A. Phillips, W.G.Rixom and T.J.Thomas.

OTHER ITEMS
HARVESTMEN (1989) Synopses of the British Fauna No. 4 (2nd ed) by Hillyard & Sankey.
Copies available from the editor (address above) at the discounted price of 15 (inc. post & packing). Hurry! Only two copies left!
WEBSITE (please note the change) for the Opiliones Recording Scheme is to be found on the British Arachnological Society's internet pages:
http://www.BritishSpiders.org.uk (capitals optional)
WEBSITE for the National Biodiversity Network is to be found at:
http://www.nbn.org.uk
Ocularium No. 4 will be published in November 2001.
Contributions received before then will be more than welcome.
FINALLY

The editor apologises if, due to pressure of work, anyone is still waiting for a reply to a letter. Thus it may be better in future to use the new email address above, if possible, for any correspondence. Thank you.


All material is Copyright British Arachnological Society and Opiliones Recording Scheme
British Arachnological Society and P.D.Hillyard 2000

Printing of this publication for educational purposes is permitted, provided that copies are not made or distributed for commercial gain, and the title of the publication and its date appear. To copy otherwise, or to republish, requires specific permission from the Editor.