Notes on Erigone longipalpis
 
Occurrence of Tm 4 on Erigone longipalpis (Sundevall) by Frances Murphy
From The Newsletter No. 9 April 1974
Being rather puzzled by a female Linyphiid, I sent it off to Mr.
David Mackie. He identified it as Erigone longipalpis (female) in
spite of the presence of trichobothria on the metatarsi on each of the
fourth legs and enclosed two specimens of E. longipalpis which he had
taken himself. Later,Mr. Mackie drew my attention to a short note
by J .H. Murgatroyd (to which his attention had been drawn by Dr. Thaler
when he visited him in Innsbruck!). Mr. Murgatroyd recounts how he was
sent 5 females from Budleigh Salterton, Devon of which 4 had trichobothria
on metatarsi 4. My husband and I looked back through our specimens
of E. longipalpis and the results, together with those of Mr. Mackie
which are the first two, are as follows:
                   
Male       Burton Point, Cheshire 1.9.55 TmIV one leg 
Female    Colne Point, Essex      5.9.58 TmIV both legs
Female    Flatford, Essex         15.9.70 TmIV both legs
Female    Flatford, Essex         15.9.70 TmIV neither leg
Male       Flatford, Essex         15.9.70 TmIV both legs
Female    R. Deben, Essex       16.9.70 TmIV neither leg
Male       Bradwell, Essex         17.9.70 TmIV one leg
Female    Bradwell, Essex         13.5.71 TmIV both legs
Male       St. Cyrus, Kincardine 26.7.71 TmIV neither leg
                               
Experienced arachnologists mostly recognise the epigyne or palp of the spider at a glance and probably never notice the anomalous trichobothrium but it can be confusing.
Possibly other members have come across similar anomalies?
Reference
Murgatroyd,. J.H. 1954 Ent. Mon. Mag» 90:231 Anomolous Specimens of
Erigone longipalpis (Sund) (Aranea, Linyphiidae)
 
Added by John Partridge at 11:24 on Tue 3rd Jan 2012.
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