Changes in the Lepidoptera of Monks Wood NNR (1974-2003)

Introduction Monks Wood has been noted for the richness of its Lepidoptera, particularly butterflies, sinceat least the middle of the 19th century. In 1828 the black hairstreak was discovered for the first time in Britain in Monks Wood. A total of 48 butterfly species have been recorded in the Monks Wood area but today only 30 species (including two non-resident migrants) can be found there. Most of the losses had occurred by the time the Monks Wood book (Steele & Welch 1973) was published (Table 1). Less is known historically about the moth fauna. Steele & Welch (1973) listed some 129 microlepidoptera and 332 macrolepidoptera (hereafter referred to as macro-moths). These records came from variety of sources collated from the many collectors who had visited Monks Wood for well over a century. The list includes some species that have not been recorded in recent decades, some of which are almost certainly extinct in the wood (Table 2). The number of microlepidoptera recorded in the wood has greatly increased but no current list has been compiled. The current list of macro-moths stands at 460 species. Monks Wood has contributed to national recording schemes for both butterflies (Butterfly Monitoring Scheme – BMS) and moths (Rothamsted Insect Survey) for three decades and it is these standardised observations that allow an examination of change within Monks Wood and a comparison with national statistics. An earlier study by Pollard and others (1998), using these data, concluded that an increase in coarse grasses had benefited Lepidoptera feeding on them at the expense of those feeding on finer grasses. Several possible causes included ride management practices, the colonisation of the wood by muntjac, and an increase in atmospheric nitrogen deposition. In the current study we examine both the butterfly transect data and the Rothamsted Insect Survey (light trap) moth data for changes over the last 30 years