Blue ground beetle

Finding a blue ground beetle in a mossy ancient wood near my home on Dartmoor in April 1996 inspired my passion for studying this fascinating group of insects.

The Blue Ground Beetle Carabus intricatus is a rare and spectacular insect that is confined to a handful of sites in Devon, Cornwall and Glamorgan. At up to 38mm long it is Britain’s largest ground beetle. Since its discovery near the Virtous Lady Mine, Double Waters, Tavistock in 1811 by W. E. Leach it has only been found at about 15 sites and has been thought to be extinct on more than one occasion. In the 1850s The Zoologist put up a reward of £5 for anyone who could rediscover it. One was eventually found by a Mrs Hayward when out walking with her husband in woods on the edge of Dartmoor in 1856, though they only received £3 10 shillings as the specimen was slightly damaged!

BCarabus intricatus larva John Walters

Clive Turner showed me how to find this elusive beetle by venturing out into its known locations on damp spring nights. Armed with a torch it is possible to find the beetles climbing tree trunks after dark. Usually a handful are seen though on one memorable evening in late May we found 36. They emerge after dark and climb the mossy trunks hunting for their favourite prey – slugs!

The beetle follow a slugs’ slime trail then, when it makes contact, its large pincer jaws grip the unfortunate mollusc. It then injects digestive juices into the slug quickly killing it and turning its insides into ‘slug soup’!

The ‘soup’ is then sucked up and within half an hour a slug as large as the beetle can be completely consumed! The larva has rarely been seen but shares the diet of the adult. I once saw one follow and kill a large Ash-black Slug (Limax cineroniger) before devouring it. View video here.

I worked on the ecology of this beetle with Clive Turner and Dave Boyce between 1996 and 2001 and have continued monitoring the known populations since then.

The beetle has appeared on television and radio several times including a search for the beetle appeared in Series 2 of Bill Oddie Goes Wild- view here and The One Show 2014 with George McGavin.

More information

Boyce, D. and Walters, J. 2001. The conservation of the Blue Ground Beetle in south-west England. British Wildlife Vol.13 Number 2, December pp101-108.

Baldock, N. and Walters, J. 2008 The Wildlife of Dartmoor page 67 - see Publications for more details.