13 June 2014

Rare ground beetles on Dartmoor: 13 June

Rachel and I met up with John Walters again this evening, this time to visit Dendles Wood - a patch of ancient oak pasture woodland situated on the southern edge of Dartmoor, to search for Britain's largest ground beetle - the Blue Ground Beetle Carabus intricatus. Blue Ground Beetles are nocturnal, spending the day in the soil and emerging after dark to climb the moss-covered oaks to hunt slugs. Spring to early summer is the best time to see them, when the adults are most active searching for mates1.

Blue Ground Beetle is an Endangered Red Data Book species now restricted to just seven sites in south-west England and a single site in Wales, with southern Dartmoor being the species stronghold. They have only ever been recorded at 15 sites in Britain, and have been considered extinct more than once2.

A couple of hours lamping moss covered oaks produced 2 Blue Ground Beetles, 1 Lesser Searcher Calosoma inquisitor devouring a caterpillar - a behaviour very rarely witnessed in the wild as this rare beetle tends to feed high in the canopy, 3 Ridged Violet Ground Beetles Carabus problematicus, and a single Moorland Ground Beetle Carabus arvensis. Also, another previously captured Lesser Searcher was released by John.

Tonight was quite dry so slugs were thin on the ground, apart from a single Leopard Slug Limax maximus. Also noted were a Nalassus laevioctostriatus - a Darkling (Tenebrionid) beetle, and a colony of Tree lungwort Lobaria pulmonaria.

Blue Ground Beetle Carabus intricatus, Dendles Wood

Lesser Searcher Calosoma inquisitor, feasting on a caterpillar (that was still alive when we first found it), Dendles Wood

Ridged Violet Ground Beetle Carabus problematicus, Dendles Wood

Moorland Ground Beetle Carabus arvensis, Dendles Wood - more commonly found on the open moor

Tree lungwort Lobaria pulmonaria - an epiphytic Lobariaceae lichen indicative of ancient forest, widely distributed across the
northern hemisphere and even recorded in tropical rainforest in Costa Rica (more here).

A huge thanks to John Walters for a fascinating and very memorable evening. I learn't a lot about these amazing insects and their ecology, and being eaten alive by midges was a small price to pay! For more information on the Blue Ground Beetle see John's website (where you can download some identification excellent guides) and the references below.

References

1 Baldock, N. & Walters, J. (2008) The Wildlife of Dartmoor. Newton Abbot: Wotton Printers.
2 Boyce, D. & Walters, J. (2001) The conservation of the Blue Ground Beetle in south-west England. British Wildlife 13: 101-108.

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