Two intrepid volunteers, Adam Sparkes and Susan Williams, joined DPA Ecological Consultant Albert Knott for a night time survey on our land at High House Waste. The aim was to record elusive Blue Ground Beetles, Britain’s largest ground beetle, at up to 38mm long. These distinctive insects are one of the rarest beetles in Britain and were believed to be extinct in the UK until 1994, when a population was confirmed on Dartmoor.
Albert told us: ‘Dartmoor is a stronghold for this rare species, and it was good to get records for High House Waste and neighboring valley woodlands. It was a dry, cool night so not the best as they prefer warm wet nights. They are reliant on lots of dead rotting wood, where they find the slugs which they feed on, and we were lucky to see a blue ground beetle eating a small slug.’
Blue Ground Beetles are mainly nocturnal and can be spotted at night-time year round, although they are most active between March and June. They like to live in ancient deciduous woodlands, such as the oak woodland lining the river valley at High House Waste, and favour damp conditions on south-facing slopes, with a plentiful supply of slugs. Both the adult beetles and their larvae feed on slugs, such as the Tree Slug and Ash-black slug. Our volunteer surveyors were lucky to see one of these rare beetles enjoying its favourite meal.
With a vibrant blue/black colouring and formidable jaws, these beetles are an impressive sight. When hunting, they follow the slime trail of a slug up a tree, until they reach the slug itself, and then seize their meal with strong pincers and inject digestive juices that turn the innards of the slug into a liquid meal. Despite having wing cases, these beetles don’t have wings and can’t fly, relying instead on their climbing abilities.
Adult Blue Ground Beetles can be spotted at night, climbing mossy tree trunks in search of prey, as has been captured in the above pictures by Adam Sparkes. Their favoured habitat has sparse ground vegetation, which is often facilitated by a healthy level of grazing, and an abundance of veteran trees and dead wood. At High House Waste, natural tree fall is permitted and the dead wood is left in-situ as a home and source of wood for wildlife.
These beetles mate and lay eggs in spring, usually in soil or other decaying organic matter. The eggs hatch quickly and the larvae then develop speedily over the course of the summer. After the larvae have fed enough on slugs they reach the required size to pupate, and then emerge as adult Blue Ground Beetles in August and September.
Buglife are running the South West Blue Ground Beetle Project, and are asking the public to send in any potential sightings. They say: ‘There’s still a lot we need to learn about the ecology of the Blue Ground Beetle, and its habitat requirements. Our South West Blue Ground Beetle project will improve our understanding of the extent and health of populations of the beetle by undertaking surveys within ancient woodland fragments across South Devon and Cornwall. By better understanding the ecology and locations of the Blue Ground Beetle, we can help conserve these populations for the future.’
The DPA run regular conservation workdays at High House Waste, and on our other land holdings, and we are always keen to welcome new volunteers to out team. If you’re passionate about caring for Dartmoor and supporting its fantastic wildlife, then one of our upcoming workdays might be exactly what you’re looking for.
Images: Adam Sparkes