I had intended to go further afield for my next Lockdown Nature Walk but events drew me back once again to the Leechwell Garden, the community garden in the centre of Totnes. I visited several times during the second week of March and discovered a fascinating story of bees, beetles and their mutual interactions.
After my account, I have included part of a poem, “The Spring”, by William Barnes written in the dialect of the west country county of Dorset.
A laughing sound, the yaffle of a green woodpecker, reached our house on several days and I thought it might be coming from the Leechwell Garden. I went to look but I didn’t find the bird. It’s no hardship, though, to visit the Garden at this time of year when the non-human world seems to be waking up and changing rapidly. On early spring mornings, it’s a very peaceful spot and the combination of old stone walls and sunshine creates a warm microenvironment. Noise from nearby roads can intrude but birdsong and the rushing of water from the stream overcome this. There are often a few children enjoying the play area, their voices blending with the song of the chaffinches flitting around the Garden.
Most shrubs and trees are in bud now but the weeping willows seem to be in the lead, their gracefully hanging branches grazing the ground in cascades of lime green. Close up, the green haze covering the branches is a mixture of immature spear-shaped leaves and catkins. The catkins are small green cigar shapes at present but will turn yellow as they mature. Towards the back of the Garden, snowy splashes of blackthorn decorate the hedges and fleshy green tongues of ramsons make their way up through the leaf litter.
Below the pergola is a sloping, southeast-facing grassy bank. When I visited, a few dandelions and daisies were pushing through the grass and the underlying soil had been exposed on part of the bank by children’s feet running excitedly towards the play area. It was March 9th, on a sunny morning, when I first noticed a few small bees flying about above this bare soil. Occasionally one of the insects paused on a leaf or flower to take the sun or to feed on nectar and I could then see their well-marked stripy abdomen. They were quite small, about two thirds the size of a honeybee and over the next few days, especially when the sun shone, the numbers increased. There were also several holes in the bare soil, some surrounded by soil spill and the bees occasionally stopped to investigate, disappearing inside the hole for a short time.
By the middle of March, a mobile cloud of the insects, at least 100 I estimated, would fly just above the soil. They moved back and forth and from side to side, circling, dancing, the urgency of movement increasing when the sun shone, like water simmering, threatening to boil over. My photos of the insects highlighted the prominent creamy hair bands around the abdomen, the pale hairs that decorate the face and sides of the thorax and the haze of pale yellow hairs coating the legs, confirming that they were male Yellow-Legged Mining bees (Andrena flavipes), one of our earliest spring solitary bees.
One day I noticed a slightly larger but otherwise similar bee pausing on a dandelion. The size suggested this might be a female and before I could take a photo my hunch was confirmed as one of the smaller bees hopped on top of the larger bee. They stayed clasped together for about two minutes, his legs twitching before they separated. She stayed on the flower whereas he moved to a nearby blade of grass. If this mating was successful, the female now starts the job of nest building. Within one of the tunnels in the bare soil she will construct a series of cells each equipped with one egg and a mixture of pollen and nectar collected from flowers. The eggs will develop into new bees. Each mated female works alone without cooperation so that these insects are referred to as solitary bees.
One of my visits to the Garden was on a sunny Sunday morning and, after I had looked at the bees, I wandered about glancing at the flowers. My attention was captured, though, by a large black beetle (about 2.5cm long) among a mass of ivy beneath a hawthorn tree. I found a second similar insect close by on a separate leaf. Both were motionless and seemed to be taking the sun. These are unusual creatures with a small head and thorax compared to their much larger abdomen. Wing cases were visible but they were too small to cover the abdomen, rather like a portly Victorian gentleman unable to secure his jacket across his belly. The prominent legs and antennae of the beetles seemed to be comprised of many small segments so that they resembled tightly coiled wire. In the sunshine, their bodies, legs and antennae sparkled a beautiful iridescent dark blue. After a bit of searching and with some kind help from John Walters, I worked out that these were female violet oil beetles (Meloe violaceus). This was a surprise as these rare insects have not been spotted in the Leechwell Garden before.
Oil beetles have one of the most bizarre life cycles of all insects, one that is inextricably intertwined with the lives of solitary bees. Each spring, mated female oil beetles dig shallow burrows in soil where they lay eggs in large numbers. The eggs develop and the louse-like, early-stage larvae, called triungulins, eventually leave the burrow. The tiny triungulins look for flowers, climb up the stems and wait in the flower for a passing solitary bee. When an unsuspecting bee arrives looking for pollen and nectar, the triungulin clambers on board and hitches a ride to the bee’s nest. Once there, it feeds on the pollen and nectar left by the bee for its own offspring and, after passing through several developmental stages, a new oil beetle emerges the following spring.
With such a complex life cycle, it’s surprising that oil beetles manage to survive, but survive they do. They are, though, declining and part of the problem is a reduction in the number of solitary bees. With urbanisation and the intensification of agriculture, wildflowers have disappeared from large parts of the countryside. Solitary bees are unable to survive in such a degraded environment with obvious knock-on effects on oil beetles.
The Leechwell Garden has a good selection of flowers, both wild and cultivated, and there are several colonies of solitary bees including the Yellow-Legged Mining Bees mentioned earlier. I hope these oil beetles will be able to continue their lives here and, as the season progresses, I shall be looking for the triungulins on flowers popular with solitary bees.
As a postscript, last Saturday morning we were walking down our street and were very surprised to find another female oil beetle. This one was crossing the road, moving quickly, antennae flexing and moving all the time as the beetle sampled the air. We stood nearby to prevent it from being squashed by cars or other passers-by. I was able to get a reasonable photo and Andrew Whitehouse kindly confirmed that this was another violet oil beetle, newly emerged.
Perhaps there are more of these insects about than I had realised?
“The spring” by William Barnes
When wintry weather’s all a-done,
An’ brooks do sparkle in the zun,
An’ naïsy-builden rooks do vlee
Wi’ sticks toward their elem tree;
When birds do zing, an’ we can zee
Upon the boughs the buds o’ spring, –
Then I’m as happy as a king,
A-vield wi’ health an’ zunsheen.
Vor then the cowslip’s hangen flow’r
A-wetted in the zunny shower,
Do grow wi’ vi’lets, sweet o’ smell,
Bezide the wood-screened graegle’s bell;
Where drushes’ aggs, wi’ sky-blue shell,
Do lie in mossy nest among
The thorns, while they do zing their zong
At evenen in the zunsheen.
[These are the first two verses of Barnes evocation of a 19th century Dorset spring. Most of the dialect becomes clear if read aloud but here are three translations: Vield – filled, graegle – bluebell, drush – thrush]