Ancient trees preserved more than 200 years ago for their landscape value have made Hertfordshire’s Panshanger Park an internationally important site for beetles that depend on dead and decaying wood.

Giving the Gerald Salisbury Memorial Lecture on 22 January, entomologist Adrian Dutton described his recent survey work at the 1,000-acre site near Hertford which confirmed the presence of rare ‘saproxylic’ beetles and discovered others not previously recorded there.

Measured against indices for rarity and ecological continuity, Panshanger Park scores among the top 20 sites in Britain for the beetles and holds international significance.

The lecture at Welwyn Civic Centre was jointly organised by the HNHS and Welwyn Natural History Society. A video recording is available on the HNHS YouTube site.

Saproxylic beetles rely on dead and decaying wood for at least part of their life-cycle. Some live inside trees where the heartwood is rotten, some are found in the bark or sapwood and others live among fungus fruits on the outside.

Out of 114 species trapped by Adrian in 2022, 45 had an official conservation designation because of their scarcity. In total 146 different types of saproxylic beetle have been found at Panshanger Park since 2000 and 166 since 1951.

He explained that ‘assemblages’ of species on this scale only occur in woodland where there has been suitable, continuous tree cover for hundreds of years. This is found in ancient forests preserved for hunting or where 18th century landscape designers – as with ‘Capability’ Brown and Humphrey Repton at Panshanger – retained mature trees for their aesthetic value.

Single trees surrounded by pasture, where their branches and canopy have spread outwards are more valuable for beetle diversity than those in more densely pack woodland.

Rare species identified at Panshanger Park include a Darkling Beetle, Pentaphyllus testaceus, that has only been located at four UK sites. Adrian’s survey also discovered impressive numbers of Click Beetle species that are very rare nationally, including Elater ferrugineus, Ampedus cardinalis and Ampedus elongatulus.

He assessed the shorter-term conservation status of the Panshanger beetles as positive,. However, their longer-term presence was in doubt because the time-gap until the next generation of trees could provide suitable habitats was too great. Experiments were taking place elsewhere to discover if young trees could be ‘veteranised’ to compensate for this.