Running a light trap as part of the Rothamsted Insect Survey

RHS project team
Dr Andrew Salisbury, RHS
Rothamsted Research
Start date
06/01/1975 00:00:00

Moth survey, Macrolepidoptera, Rothamsted light trap, RHS Garden Wisley, Rothamsted insect survey

The problem

Long-term monitoring of the distribution and abundance of animals indicate changes in the health of ecosystems that underpin human welfare. An analysis of the data set generated by the network of traps from 1968 to 2007 carried out in conjunction with Butterfly Conservation, generated national population trends for 337 species of common macromoths. Worryingly, two-thirds show decreasing population trends over the 40-year period, while one third showed increases (see the report on The State of Britain's Larger Moths 2013).

A wide range of drivers for the declines have been suggested including habitat loss and fragmentation, climate change, agricultural intensification, urbanization and light pollution. Of these evidence indicates that habitat destruction and degradation and climate change may be the most important (see the online abstract for the Journal of Applied Ecology - Fox et al. 2014) although further research is on-going. Included in the species that are increasing in abundance are more than 100 that were not previously found in Britain. It is important to record the arrival and spread of new species, as they may become pests or pose a threat to native wildlife.


Rothamsted light traps are run on every night throughout the year. The earliest moth records date back to 1933 from a trap on Rothamsted Farm, near Harpenden, Herts, and a national network has been in operation since 1968.

A Rothamsted light trap has been running at RHS Garden Wisley since 29 May 1975 and is now one of the longest consistently running traps. It is situated near the Propagation glasshouses. The macromoths are identified and counted by a volunteer, and the data are sent to Rothamsted Research. To date, more than 400 species of larger moth have been recorded in the Wisley trap. In addition to the macromoths, the smaller (micro) moths, lacewings (Neuroptera), beetles, true bugs and leafhoppers are identified and counted.

Benefits to gardeners

Active involvement in a long-term survey, such as the Rothamsted Insect Survey, is vital in order to determine changes and trends in UK biodiversity, particularly in the light of climate change. The Rothamsted light trap network is organised by Rothamsted Research and run with the help of volunteers at about 80 sites in the UK. It is used primarily to monitor the distribution, flight period and abundance of the larger (macro) moths. Macro-moths are essential to the food chain and can provide pollination services.

Further information

Moths: Encouraging into your garden

Rothamsted Insect Survey

Andrew Salisbury, RHS

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