The Marsh Gibbon RIS Trap

The Rothamsted Insect Survey celebrated its 50th anniversary in 2014.  This nationwide system of light traps was established in the early 1960s in an attempt to better understand moth population changes.  Further information on the origins and development of the survey can be found in an article by Ian Woiwod et al here and in another article on the Biotechnology & Biological Sciences Research Council website here. 

 

Rothamsted light traps are identical fixed traps which use a 200wt clear tungsten bulb.  The nightly catch falls into a collecting jar laced with Tetrachloroethylene which kills the insects.  For consistency, even in these more conservation–conscious days, it is necessary to continue the collection of dead insects using the same type of bulb in order to make sense of the invaluable data provided, but in defence of the network it should be pointed out that the tungsten bulbs pull in samples which are far smaller than the MV or actinic light traps used by enthusiasts today.   

 

The national network currently consists of some 80 or so traps.  Changes in circumstances have meant that few of those running today have been in operation since the very start of the survey.  In Bucks the first trap began operation in Chesham during 1968 but only lasted until the following year.  The 1970s saw several traps set up in the north of the county during the development of Milton Keynes, one in Howe Park Wood providing more than 15,000 records over eight years, but they had all been closed down by the end of that decade.  A light was run at Chalfont St Giles from 1981 until 1985 but thereafter there were no more RIS traps in the county until 2001 when the Burnham Beeches example began collecting data.  It was joined by the trap at Marsh Gibbon in 2006 and these two are still running today.

Location:	Trap:	Grid reference:	Period:
Bletchley Park	144	SP 863337	1970-1974
Bletchley	150	SP 866336	1971-1972
Bradwell Abbey	354	SP 827395	1977-1978
Burnham Beeches	588	SU 945845	2001-current
Chalfont St Giles	435	SU 986935	1981-1985
Chesham	110	SU 960020	1968-1969
Howe Park Wood	170	SP 831342	1970-1977
Marsh Gibbon	629	SP 647210	2006-current
Shenley Brook End I	145	SP 835355	1969-1974
Shenley Brook End II	297	SP 837355	1974
Simpson I	147	SP 878367	1970-1972
Simpson II	155	SP 878366	1975
Stony Stratford	143	SP 792405	1970

Located on the clay of the Vale of Aylesbury in the north-west of the county, trap 629 is sited on a field margin adjacent to a tall mixed hedgerow on a working farm to the south of Marsh Gibbon.  In contrast to the Burnham Beeches trap the habitat at Marsh Gibbon is unremarkable and the species list had reached only 255 moths by the end of 2012 (251 macros but just 4 micros).  The Rothamsted survey concentrates only on the macro-moth species but, co-incident with me taking over identification of each nightly catch during 2013, a greater effort has now been made to sort through the ‘by-catch’ and the list now stands at 430 moth species (263 macros and 167 micros). 

  

 

Although most of the species on the list are common and widespread, the site has produced one or two nice moths.  Garden Tiger Arctia caja still puts in occasional appearances, averaging a sighting every other year which makes this one of the most consistent sites in Bucks for a rapidly-declining species.  Lappet Gastropacha quercifolia and Double Dart Graphiphora augur also turn up regularly.  Twin-spotted Wainscot Archanara geminipuncta and Brown-veined Wainscot Archanara dissoluta have each visited the trap but this is quite a low-lying area and there are plenty of reeds in the roadside ditches south of the farm down towards the River Ray.  The most pleasing finds in 2014 were Cream-bordered Green Pea Earias clorana on 22nd July and Oak Eggar Lasiocampa quercus on 26th July, neither of which had been previously recorded at the site.  No exceptional micro-moths have yet been discovered but at least the list of species is now making decent progress.

 

Cream-bordered Green Pea