Notes on Porrhomma errans
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SOME REMARKS ON PORRHOMMA ERRANS (BLACKWALL) by J.R. Parker
From The Newsletter No 15 May 1976
It is through the kindness of Dr. Colin G. Butler of Rothamsted Experimental Station that I am able to write that which follows.
Porrhomma errans is a rare species and seems to have been recorded only from nine British and two Irish counties. During the past two years Dr. Butler has collected specimens of this species in pitfall traps on Park Grass Plots, Rothamsted, Harpendea. Hertfordshire, as follows: One female, June 1974; two males, 13th. February, 1976, two males, 28th. February, 1976 and one male in March 1976. Dr. Butler kindly sent to me specimens for examination and wondered whether his identification was correct because he submitted that the Tm.I position for his specimens is ca 0.6 and not ca 0.4 as stated by Locket and Millidge (1953). I agree that Dr. Butler is correct for the Rothamsted specimens. The spinal armature of the legs agrees with that detailed by Jackson (1911/1912) and by Locket and Millidge. To quote Jackson: 'All the metatarsi bear a long strong spine above the base. This is absolutely characteristic of the species as here defined'.
It will be noted that Dr. Butler's male speciens were all taken in the early spring which is that time of the year remarked upon by other recorders including 0. Pickard-Cambridge who state that specimens have been observed running on railings and trees, presumably following an aerial dispersal. It would appear however, that grassland is the normal habitat and I have a note relative to Hull's record at Ninebanks, Northumberland: "Taken from under inverted flower pots in grass below fruit trees'. It may well be that P. errans is a stenochronus species with adult activity in the late Winter and early Spring.
Because the species is not recorded for Hertfordshire on its distribution map in Locket, Millidge & Merrett (1974) I thought that Dr. Butler's records must be new for that county. However, Jackson cites a record for Hoddesdon in Hertfordshire, and states: 'I only include localities for those specimens which I myself have seen and identified'. One other minor correction: Jackson's paper: 'On the Genus Porrhomma Simon' is part II of his publication 'On some new and obscure British Spiders' in the Transactions of the Nottingham Naturalists' Society for 1911-1912, not for 1913 as stated in British Spiders Vol.II.
O.P-Cambridge, (1879-81) The Spiders of Dorset. Sherborne.
Jackson, A.R. (1911-12) On Some New and Obscure British Spiders. Trans. Notting. Nat. Soc. 60 pp. 20-49.
Millidge, A.F. & Locket, G.H., (1953) British Spiders Vol.II. Ray Soc. Lond.
Millidge, A.F. Locket, G.H. & Merrett, P., (1974) British Spiders Vol.III Ray. Soc. Lond.
Added by John Partridge at 16:31 on Wed 4th Jan 2012. Return to Summary for Porrhomma errans