Long-horned bees on the south Devon coast

One of my favourite parts of the coast path in south Devon is the section between Prawle Point and Start Point.   Between these two imposing coastal landmarks the path follows the meandering line of the low cliffs and, unusually for this part of Devon, there are few hills and walking is easy.  The area inland of the coast path is notable for the line of steep rocky cliffs that, many years ago, formed the coastline when sea levels were higher.  Between these inland cliffs and the present coastline is a flattish area, about a field’s width across, mostly used for pasture and arable farming.  One section, a long curving coastal meadow (above Horseley Cove), is left uncultivated and many wild flowers grow here and, to a lesser extent, along the edges of other parts of the coast path.   With the rocky coastline and rugged inland cliffs, the area retains a wildness and I come here to be close to the sea and to immerse myself in nature in all its fullness.     

View of part of the site looking towards Peartree Point and the east, showing the rugged inland cliffs, the flattish arable fields and the present coastline with low cliffs. The flowery coastal meadow is to the right, just out of the picture.

View of part of the site looking west to Prawle Point showing the inland cliffs and the present coastline.

The stretch of coastline between Start Point and Prawle Point is a nationally important site for rare invertebrates and was designated as a Site of Special Scientific Interest (SSSI) in 1986.   For some years now, I have been coming here in early summer to watch the rare long-horned bees (Eucera longicornis) (see here as well) that use the soft rock cliffs for nest sites and forage from the wild peas and vetches that flourish in this environment.  The area is also a stronghold for the cirl bunting and I often see and hear these rare birds when I visit.   If I am lucky, I may also see seals swimming nearby or basking on the rocks at Peartree Point .

Earlier this year, in April, I walked along this section of the coast path and was alarmed at what I found.  The long curving coastal meadow, filled with wildflowers later in the year, was intact but outside of this area there was considerable evidence of herbicide use.  Some fields to the east of the meadow and the paths around them had been drenched with herbicide prior to planting new crops. The chemicals had reached the hedges that line the sides of the coast path and the area looked barren and dried out (picture below).   To the west, where the coast path runs between the cliff edge and arable fields, there had been spot spraying of “weeds”.  It looked as though attempts were being made to eliminate wildflowers alongside areas where crops are grown.

Wildflowers are very important for supporting the insects and, indirectly, the birds that flourish here and I was concerned by this apparent degradation of the site.  I decided to make several visits across the summer to see how the site recovered and how the insects fared.

My first visit was in late May and I found good numbers of male long-horned bees in the coastal meadow, foraging mainly on bush vetch.  This flower scrambles through the bracken that lines the cliff edge of the meadow.  With its slightly untidy looking flowers that start a deep purple  but open to pale lilac petals, bush vetch provides excellent early forage (picture below).  The long-horned males looked very fresh with their yellow face, bright russet thorax, shiny black abdomen, legs coated with fine hairs and their trademark very long, shiny, black antennae.  They are such iconic, beautiful creatures and it was a pleasure to see them moving swiftly about the site between flowers.   I also went to look at the nest area in the soft rock cliffs below the meadow where the vertical, reddish surface is peppered with pencil-sized holes.  Males appeared here regularly looking about the site for females.  They arrived and performed a meandering flight across the nest area, sometimes repeating this before flying off.  There was some play-fighting and a few overexcited males got tired of waiting and tried to mate with their male cousins. 

The coastal meadow on a dull day showing the edge of the inland cliffs and the cliff top bracken

The coastal meadow on a sunny day showing the mass of wildflowers and grasses

The coastal meadow looked glorious.  A dense coating of knee-high grasses grew across the site lending it a sheen of pale browns, greens and muted reds.  Many flowers grew among the grasses in addition to the bush vetch, including buttercup, catsear, common vetch, speedwell, hop trefoil, wild carrot and along the cliff edge to the western end, bird’s foot trefoil, thrift and bloody cranesbill, a rich kaleidoscope of colours .   For the most part, herbicide-treated areas outside the meadow had grown back although some flowers had been eliminated.

Female Eucera longicornis appeared in June and by the third week of the month they outnumbered males.  One hot spot for females was a hedge along the sea side of the coast path where it skirted a field just to the east of the flowery meadow.  Narrow-leaved everlasting pea grew here in moderate amounts, its bright pink flowers proving very attractive to the females.  I watched them feeding from the flowers; they looked rather different from the males, their antennae were a more conventional length and they appeared chunkier with striking golden plumes of pollen-collecting hair on their back legs.  When they arrived, they landed on the lip of the flower pushing the large sail-like upper petal backwards to access nectar.  Narrow-leaved everlasting pea also grew through the cliff edge bracken in the coastal meadow and female long-horned bees were foraging there too.   Although many other flowers were growing here including several large patches of the yellow scrambling meadow vetchling, the females showed an absolute preference for the wild pea.  I also spent some time by the nest area watching a regular stream of females returning to their nest, some carrying large lumps of sticky pollen on their back legs.  A few males hung about the nest site and others foraged from bush vetch in the meadow but they paid little attention to the females, all mated by now. 

The rocky coastline just above the nest site showing bird’s foot trefoil and thrift

Although the coastal meadow was still looking outstanding with its rich fabric of grasses embroidered by so many wildflowers, the situation elsewhere on the site was not as encouraging.  Wilting plants in several locations indicated more herbicide usage and the path along the coastal hedge mentioned earlier had been strimmed on the sea side and treated with herbicide again on the field side (more wilting plants, pictures below).  To cap all of this, when I visited in the second week of July, cattle had been allowed into this area trashing the hedge and eating all the narrow leaved everlasting pea growing there.   In previous years, this hedge and the wild pea that grows here have been critical for the survival of the female long-horned bees so this could have been catastrophic.  Fortunately, this year large amounts of the wild pea with its bright pink flowers had grown up in the coastal meadow and many females were foraging there instead.   

So, based simply on this year’s observations and the numbers I saw, the long-horned bees seem to be doing well at this south Devon site.  The colony is moderate in size and numbers seem to be holding compared with observations made in previous years.

There has, though, been significant degradation of the local environment this year with loss of wildflowers following herbicide use and cattle damage to an extent I had not seen before.   In order to support these rare bees and perhaps to increase the size and extent of the colony of long-horned bees, the numbers of wild flowers should be increasing along the length of the coast path rather than being restricted to the coastal meadow as currently seems to be happening.   This degradation of the site surely runs counter to the legal protections associated with an SSSI?

Another concern at this site is the fate of the six banded nomad bee (Nomada sexfasciata), the UK’s rarest bee.   This bee is a parasite of Eucera longicornis and in the UK is only known at this south Devon site.  I last saw it in 2017 when I made several sightings.  Since then, it has been seen by others on only one occasion each subsequent year so it is very rare.  This year, I saw several Nomada species by the nest area in late June.  One stayed for a short time but was definitely not Nomada sexfasciata and the others disappeared too quickly for verification.  I believe there have been no other sightings this year. 

The south Devon site needs support to protect the unique flora and fauna present there, especially the rare bees and other insects that live in this special habitat.  Buglife and the South Devon Area of Outstanding Natural Beauty are developing a project termed Life on the Edge which aims to protect the site and increase the number of wildflowers.  It is currently seeking funding so we have to hope it gets that support.

The bees

Male Eucera longicornis on bush vetch (early June)

Male Eucera longicornis on narrow-leaved everlasting pea (late June)

Two males by the nest site in early June

Female Eucera longicornis on narrow-leaved everlasting pea showing pollen hairs on her back legs (late June)

Female Eucera longicornis approaching narrow-leaved everlasting pea flower (late June)

The state of the site across spring and summer

Herbicide damage in April (SX785360)

Strimming in June (SX785360)

Herbicide use in June (SX785360)

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Cattle damage along hedge showing remains of narrow-leaved everlasting pea (July, SX785360))

The featured image at the head of this post shows a male Eucera longicornis on bird’s foot trefoil in late May.