Bees, ants and wasps

To read more please go to the Sidmouth to Dorset coastal wildbelt group page. 

Two species, the brown-banded carder bumblebee and the moss carder bumblebee, are listed as Devon Special Species. They’ve undergone a serious national decline since the 1970s and the Devon populations are nationally important.   

Carder bumblebees need a range of flowering plants, in particular those with long tubular flowers (they have long tongues) such as clovers and peas, as well as being recorded on mint, figwort and the daisy family. Both species nest on or just below the ground among long grass or mossy vegetation. Studies have identified a clear requirement for extensive, well-connected flowery habitats near to rough grassland nesting sites. 

This wasp is restricted to lowland heathland sites across southern England, from Devon to Sussex. It needs warm, dry sandy lowland heaths, and a source of clay. In Devon it’s only known to be in the Pebblebed and Bovey Basin heaths. 

Heath potter wasps are known for (and named after) the unique vase-like structures the females build in which to lay their eggs. To construct the 10-25 pots she will make in her short lifetime (just two to three months), the female needs a site that has water and clay, with heather, gorse and grass nearby. Females lay an egg inside each pot and add up to 38 moth caterpillars, creating a larder for the wasp larva when it hatches. Moth caterpillar species the wasps prefer are the double-striped pug (Gymnoscelis rufifasciata) and the narrow-winged pug (Eupithecia nanata), which feed on gorse, heather and holly. 

The heath potter wasp is so closely associated with lowland heaths that it serves as a valuable indicator of heathland habitat quality.

The narrow-headed ant is nationally endangered. In the UK it’s only found in Devon at Chudleigh Knighton Heath SSSISite of Special Scientific Interest More and the adjacent road verges, and at a few sites in the Scottish Highlands. 

In Devon, the ants build south-facing domed nests, typically in tussocks of grass at the edges of scrub on heathland. Their nests are often close to small trees, on which they ‘farm’ aphids. The aphids feed on plant sap which they cannot wholly digest, excreting some as sugar-rich honeydew, which the ants feed on. The ants guard this valuable food source, in the process protecting the aphids from predators. 

Compared to some other ant nests, narrow-headed ant nests are typically small, containing around 1000-6000 workers. Nest colonies can be quite mobile, quickly dismantling the nests to move them to a sunnier spot, or setting up temporary satellite nests to take advantage of seasonal resources. This means it can be harder to monitor and be certain of the precise number of nest colonies.

With heathland habitat loss and fragmentation, suitable habitats are far apart and the species cannot naturally disperse to other sites or former sites in Devon. Threats include scrub encroaching onto nesting areas smothering nests, and nest structures being repeatedly damaged during road verge maintenance clearance. A potential future threat comes from mineral extraction rights at Chudleigh Knighton Heath  which will destroy nests directly as well as heathland habitat, on what is the species’ only remaining site in England.

This bumblebee is also known as the mountain bumblebee as it’s found in uplands among habitat mosaics of flower-rich grassland, and upland heaths and moors with bilberry.  

Bilberry and willow flowers are particularly important in spring when the queens first fly. Other key plants for the species include bell heather, ling, bird’s-foot trefoil, clovers and bramble. Bilberry bumblebees nest in fairly small colonies of around 50 workers in old mammal burrows.

Once widespread in uplands, the bee is now facing serious declines. This is thought to be due to habitat loss and its vulnerability to climate change, as it is dependent on high altitude habitats and has a low heat tolerance. Other threats are from winter overgrazing of the bilberry plants (which only flower on older mature stems), removing a crucial foraging resource in spring, and fertilising of flower-rich grasslands near to upland nesting areas, leading to flowers being overtaken by grasses. The bilberry bumblebee is therefore a valuable indicator of a healthy, wildlife-rich upland landscape.  

Devon has two of the few upland moorland areas in the south of England making it of national importance for the species. There is only limited information about the full current distribution and status of the bilberry bumblebee in Devon, other than locations of past and some recent records from Dartmoor and Exmoor.

To read more please go to the Start Point to Bolt Tail invertebrate page.