A Simple, Slow-diffusion Method for Clearing

Nero.s/.

6

Br. orachnol. Soc, 64

First record of the Linyphiid Spider Entelecara omísso O.P.- Cambridge on the European Mainland

I thank Rob Bosmans and Jean-Pierre Maelfair :or their affirmation of the idenöfication. Withour the ccmpany of Luc Daniels. Deborah Procter and Anciir Fo-er.

by Kris Decleer

more years.

On l0th Juiy' i991 one female specimen oÍ Entelecora omisso was;cund dunng an excursion to the'De Maten' nafure reseru-e ln the province of 'Limburg' (municipalit-v of Genk. UT)'Í-square FS74). This reserve of more than 170 hectare :s characierised by a system of intercon-

References

necred shaiiow'ponds wirh associated marshland vegetation. set in rhe midcjle of a heathland landscape. Apart from some europhic ponds, the water quality of most ponds is mesouophic. The marshland vegetation is very

diverse. va+-lng from Caru. vegetation, reedbeds. Typho stanis and Juncus vegetaton to alder carr and Myico gole scrub. The management of the ponds is unusual. Foiicwing àe local custom of the Campine area. each pcnd is empded every two to ten years for a penoci of one :o two y'ears by the removal of small locks or ciams. Hi-oricall-1, rhis was done to harveí the local fish popuiaoci and it was often followed by a period of arabie farmrnc before \&?ter was let in again. Nowadays. this panicuiar :orm oí rnanagement is carried out mainly

ro ercourage

àe

interesring pioneer vegetation which

cievelops aiie: emptyng tàe pond. Enrclecorc omisso was captured by hand amongst the pioneer vege:ation. malnly consisflng of Juncus bulbo-

sus and l-i'r-crocofi;le uulgais, of an emptied pond. Locally. parcres of Juncus effusus, Alisma plantagoaquorica. Baiiellia ranunculoides aod Typho latifolía were preseni. Other parricular plant species on the site were Littorellc uniflora. Utriculaia ausfrolis urd Cicendia filíformis. The pond was fringed with reed which

connected ir io the marsh vegetation of adjacent ponds. The pond w- emptÍeci during spring 1990 and it was planned to Ílood it again at the end of 1991. It is most Iikely. therefore. that the specimen was a vagmnt from neighbouring :narshland.

According :o Heimer & Nentwig (1991), E. omisso is only known ;rom the British lsles. In his review of the nationally nciable spiciers of Great Britain. Merrett (1990) gives nore derails on its ecology and distribution. Aduls are mo;Jy found in May and June, but also in autumn. The species seems to be abundant at several English sites. and is apparently widespread in the fens

the species may well have stayed undiscovered for n:a:'li'

Gryseels, M., Decleer. K Vyve-v Q,. Anselin. A & Va:: Su-aa:e::, ) (1989) Moerassen en Open warer. In Hermy. M, e: , Nan::==heer. Van de Wiele. Stichnng Leefmilieu. :-aruu::eserva:e:- ::r Institut voor Natuurbehouo. Brugge. Heimer, S & Nentwig, W (1991) Spinnm Mítteieuropcs lrerlag ?=:i Parey, Berlin and Hamburg Merrett, P (1990) A Reuiew of the Nononolly Nonble S=:aers oj C'=:: Britoin. Nature Conservanry Council. Conrract S'*-.e-"- No --i N.C C., Peterborough

Laboratonum voor Ekologie cier Dieren, Zoögeogmrtz houd, Ledenganckstraat 35, 9000 GENT. Belgum

:r Nar:'::::-

A Simple, Slow-diffusion Method for

Clearing

Small Arthropods by Mark Judson Small arthropods are usuaily best studieci n :ernpc-::-; mounts, using the open-slide technique cescribec :-,, Grandjean (1949) and Coineau (7974). Many,' types :i media have been used to ciear specimens: giyce:-:?. lactic acid and clove oil being the most pccular ';-.-.r arachnologists. However. small and deiicare soeclre :.s often collapse when tansferred from alcoilol tc --:e clearing medium, due to the osmotic suess invc,'.e:. Specimens in iacric acici can usuaiiy be excandec :1' gentle heating (Grandjean. 1949), but this somei:r.es damages delicate strucrures and can cause frag.e specimens to burst.

To avoid this problem. I have emplog,ed 'àe iollcr,'-:.rg simple method when working with weaklg'-scleroasec pseudoscorpions. A short length oÍ giass rubing ie.g. length 12 mm, diameter 3 mm) is cut anci then stoppe:eci at one end with cotton wool. The specimen in alcchol is pipetted into the tubing which is then sealed '*-ró

cotton wool at the other end. The whole microviai

ls

oÍ SufÍolk anci Norfolk. This is confirmed by recent (D P:octer. pers. comm.). E. omissa is also knour from Cambridgeshire, Dorset, Sussex, Kent and

studies

Yorkhire. The species has been found amongst Corex russock. plant detrirus. and other marsh vegetation tvpe- Dunng a spring visit in 1991 to the Norfolk Broads within the framework of a British-Flemish exchange

progr:amme with fieid researchers from the Nature Con-=rvanc-r' Council for England, E. omisso was collected trom Cladíum vegetation. Having seen several other E. omissc localiues in the Broads, and in view of the record in 'De Maten'. this linyphiid spider may be con,.idered as an indicaror of mesotrophic conditions. It seems likel-r'aat the species may occur in a wide range of marshlanc vegetadon types. It is well known that mesorophic ri'edands have almost disappeared in FIanders (Grysee .s et al. 1989) and form one of the most rhreatened habitats in Westem Europe. Together with the small sue of the spider (7.25-7.70 mm) this may perhaps expiarn why E. omisso has not previously been found on the continent-

7.

Stoppered microoiol containíng speamen cleonng medium.

Figure

n tuoe ci