The Saxons are invading again

In July 1987, Dolichovespula saxonica, commonly known as the Saxon wasp, was first recorded in the UK at Juniper Hall in Surrey. In the 32 years that has since passed, the species has spread throughout south-eastern England, with scattered records further north to Yorkshire and a handful of sightings from Scotland. Eventually, at the end of July this year, I saw my first ever Saxon wasp, in the same county it was first seen. It is one of two social wasp species which have colonised the UK in modern times, along with Dolichovespula media, the median wasp, which was first found by Steven Falk in 1980 in Sussex.

Contrary to what many people might expect, there are several thousand wasp species in the UK, ranging from tiny parasitic wasps which barely reach 0.2mm in length to the docile hornet. Most of these wasps are solitary, and the social wasps comprise only about 1% of all the world’s wasp species. They’re mainly restricted to the subfamily Vespinae, which has around 11 members in the UK.

My recent sighting of the Saxon wasp came as quite a surprise to me. In the past few weeks I’ve been noticing more broad-leaved helleborines Epipactis helleborine (a species of orchid) than I usually do in my local area. They like to grow beside paths within woodland, perhaps due to the increased amount of light that reaches their leaves in comparison to the centre of the dense woodland. As a result, they are one of the most frequently encountered orchids in my region. However, despite their frequency, before I found my first Saxon wasp I had never observed any pollinators visiting these orchids.

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A spike of the broad-leaved helleborine on my neighbour’s verge

As you can see from the photo, their flowers are not particularly attractive colour-wise. Many other orchid species have evolved to mimic their pollinators, so that they are not drawn to the flowers by the promise of a meal but by the promise of a mate; as a bee, for example, attempts to mate with the flower of a bee orchid, pollination will take place. Moreover, the flowers emit a scent mimicking the pheromones emitted by the female bee, attracting the pollinating bees from far afield. This may sound clever, however reducing your number of pollinators to just one or a handful of species greatly restricts spread. Indeed, in southern England, the pollinator of the bee orchid is quite rare, and most of the time the bee orchid reproduces by self-pollination.

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The early spider-orchid, despite its name, has evolved to mimic the mining bee Andrena nigroaenea. I can’t personally see the similarity, but perhaps the bees can.

However, the broad-leaved helleborine does it slightly differently. Its primary pollinators are social wasps, such as the common wasp Vespa vulgaris (one’s standard picnic-botherer) as well as the Saxon wasp. Like many flowers it produces a nectar to entice the wasps in. However, once the wasps have arrived at the orchid flowers, they begin to become intoxicated by traces of opioids within the nectar. The narcotic-like qualities of the nectar cause the wasp to sleepily visit all of the flowers on the orchid multiple times, to ensure that all the pollinia from the flowers are transferred. I like to think that the opioids are also addictive to the wasps to encourage them to visit other broad-leaved helleborines, but I’m not sure whether this has been studied yet!

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A drugged Saxon wasp walking between helleborine flowers.

In the photo of the wasp above, it is quite easy to see a number of white objects on the face of the insect. These are the pollinia of the orchid, which stick to the face of the wasp after it has visited each flower trying to reach the nectar within. Each individual flower only has a few pollinia, which is the whole product of an anther. It is a coherent mass of pollen which is attached to the flower by a stipe (or stalk) and has a sticky disk on the other end which attaches to the face of the insect. Ideally, the insect then transfers these masses of pollinia to another plant, where the pollen in the pollinia will be transferred to the stigmata, completing pollination.

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The wasp reaching into a helleborine flower, looking for nectar. The pollinia can be seen just above the thorax of the wasp, attached to the roof of the flower, ready to attach to the wasp. 

It was fascinating to document this sighting, which was two firsts in one: my first Saxon wasp, and my first observation of pollinia in action. I’ll be keeping an eye on the helleborines this summer to see if any other wasps are enticed to the flowers by the sweet nectar and drugs!

Orchid on the Hill

The Early Spider-orchids Ophrys sphegodes at Castle Hill NNR have one of the best views of the South Downs as well as Brighton to their south-west. On the northern edge of Woodingdean, a chalk grassland slope supports this nationally scarce species, which has only a scattered distribution along the South Coast from Dorset to Kent.

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This orchid is named after its appearance, with its flowers apparently resembling the abdomen of orb-weaver spiders. However, its flower shape has evolved so that it resembles bees, which come to try and mate with the flower, known as pseudo-copulation. This is also the case in the perhaps more appropriately named Bee Orchid for example. To complement the shape of the flower, these orchids also release the scent of female bees which further entices the male bees to unknowingly pollinate the plants.

However this technique may show to be detrimental towards the success of the species in the face of climate change. Despite the strength and accuracy of the scents wafted by the flower, they cannot compete with actual female bees. Therefore, the plants most likely to pollinate and reproduce successfully are those which blossom after the male bee has emerged although before the females. Although sadly warmer spring temperatures are pushing the phenology (life cycles) of these two species out of sync.

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It is also interesting to observe the variation in the exquisite patterns shown on different individual flowers, such as these:

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Travelling to find these orchids (a new plant for me) was a perfect break from revision. Despite their rarity, there are several reliable sites such as Durlston Country Park and Dancing Ledge in Dorset, Samphire Hoe in Kent and of course where I visited today, Castle Hill NNR in East Sussex. I would definitely recommend looking for them before they stop flowering in early June!

 

Christ’s blood covers the Lords-and-Ladies

Being only mid-April it is quite early for a number of wildflower species to be blooming, in particular Orchids. Therefore I was very pleased when I spotted quite a number of individual orchid plants, or ‘spikes’, on Good Friday.

The colour of the flowers of these orchids were purple, and they were flowering quite early in the orchid season. That meant that they were Early Purple Orchids! I was pleased that I managed to see these orchids as although they are not a particularly rare or localised species, they are a species I have never seen before.

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Early Purple Orchid (Orchis mascula) whole spike

 

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Early Purple Orchid (Orchis mascula) flower detail

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Early Purple Orchid (Orchis mascula) whole plant

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Early Purple Orchid (Orchis mascula) leaf detail

As you can see from the last photo above, the leaves of this species are covered in dark black markings. Early Purple Orchids share this characteristic with several other orchid species such as the Common Spotted Orchid and the Heath Spotted Orchid. And, as there so often is, there is folklore that surrounds the spots that are present on the Early Purple Orchid. It has been believed that this flower grew below the Cross on which Christ was crucified, and the leaf spots are the drops of Christ’s blood.

And not only orchids have these dark spots on their leaves. We came across these leaves on the same walk:

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These are the leaves of Lords-and-Ladies, Arum maculatum. When the scientific name is translated into English it becomes ‘Spotted Lily’, after the spots on the leaves. Along with Lords-and-Ladies there is a huge range of other vernacular names including Cuckoo Pint, Jack-in-the-Pulpit, Cows-and-bulls and Naked Boys. The names that are gender-related such as Lords-and-Ladies and Cows-and-bulls refer to how the flowers of this species apparently look like the process of sexual reproduction:

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The flower is very clever in attracting insects for pollination. The spadix, the dark inflorescence rising vertically from the flower, has an odour resembling that of dung which is particularly attractive to a number of fly species. The flower can also produce a temperature significantly warmer, up to 15 degrees or so, than the surrounding air, which also helps to bring in pollinators. Below the spadix there is a ring of robust hairs, which temporarily keep the flies inside. The flies are able to escape but usually only when they have come into contact with the male flowers inside the spathe (the green hood surrounding the spadix) and have therefore been covered in pollen. Once the fly has escaped then it will fly to another Lords-and-ladies flower, again attracted by the faecal scent. Some of the pollen on the fly will find itself inside the female flowers – which are situated below the male flowers – allowing fertilisation to take place.

Both Early Purple Orchids and Lords-and-ladies are common plants in the UK at this time of year, definitely species to look out for. Early Purple Orchids are easy to spot due to their tall and bright flowers, particularly in their favoured habitat of woodland and woodland edge. Lords-and-ladies are less easy to spot due to the green colour of their leaves, however keep an eye out for them and you should be able to find some of the distinctive flowers.

 

 

Worms from the depths…

Last weekend, on the way back from a great stay at Portland Bird Observatory, I met Tony Davis and Josie Hewitt in a small car park in the New Forest. Our aim was to find as many rare plants as possible and we did well, finding really uncommon species such as Yellow Centaury, Pillwort and the delightfully named Duck-potato. Below are a few photos of the plants we managed to record.

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Autumn Lady’s-tresses

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Pillwort, this is actually a fern and reproduces using spores!

Despite seeing over 30 new species for my pan-species list that day my highlight was actually an annelid worm! I don’t often look at annelid worms (which are mostly earthworms) as they are not the most exciting creatures in my opinion and I find them very tricky to identify. However the species I added was far from boring!

To find this species, we stood in a pond.

We didn’t have to do anything else, just stand in the pond and wiggle our feet. It wasn’t long before I spotted a long dark creature swimming towards me like an eel on its side. It twisted through the water and came right up to my boot before swimming off. Then Josie spotted another at my heel. There were several of them, twisting through the water weeds with elegant wavelike movements.

This part of the New Forest is excellent for this species of annelid worm, the Medicinal Leech. This is due to the number of ponies providing the leeches with lots of food! Many leeches are terrestrial, however some, like this species, prefer to inhabit freshwater and are adept at swimming. The Medicinal Leech is often mistaken for the Horse Leech, which the leeches in this pond were at first thought to be. Although they appear very similar in appearance, they have very different prey preferences. Despite the name, Horse Leeches can’t penetrate the tough skin on mammals and therefore cannot feed upon their blood. Instead they choose to eat much smaller prey, such as snails and earthworms, both in the water and out. Medicinal Leeches are able to bite tough skin and their main food sources are cattle and horses. However, they also feed on frogs and sometimes even humans!

Unfortunately, these fascinating invertebrates are one of the few I know to have an IUCN designation worse than Least Concern. Most are Not Evaluated or Data Deficient and the species with enough research to provide details on the fluctuations and size of populations are often not too rare. They are classified as Near Threatened despite the population trend – among other things – being unknown. Their main threats are local collection for medicinal use; loss of habitat; and decline in one of their main prey items, frogs.

Below are a few photos I was able to take of the leeches that swam towards us:

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Underground Birds’ Nests!

This afternoon I was very lucky to be able to fit in a short trip to an undisclosed site in Ashdown Forest to see a very rare plant: the Bird’s-nest Orchid. I have been asked to keep the precise location a secret as there are only two individual plants flowering at the moment and I believe there might be some collectors keen to get their hands on them. Luckily Ashdown Forest is a huge place and these orchids are incredibly easy to miss.

I first learnt about these orchids being present at Ashdown Forest – one of the largest areas of woodland and more importantly open heathland in the South East – on the Sussex Botanical Recording Society website. There is a new ‘Latest Sightings’ feature on the website and I have been lucky enough to post a ‘Latest Sighting’ on there already, on the Krauss’s Clubmoss. You can read the orchid latest sighting here and my clubmoss latest sighting here.

The beech woodland where the plant was growing was very nice except there was very little diversity of ground flora. I think this may be due to the very large population of deer, particularly the Fallow Deer, which have over-grazed the area. However, there were some nice patches of late-flowering Bluebells as well as Ground Ivy, Germander Speedwell and not-yet-flowering Wood-Sorrel. In fact I saw a couple of female Fallow Deer while we were there, although they were very shy and were gone before I could see more than their heads with their sensitive ears standing up rigidly, on high alert. Deer were hunted in Ashdown Forest in the past so they must have learnt to be very wary of humans even now when deer-hunting has been discontinued.

There were some very large and beautiful Beech trees in the woodland that seemed to support a plethora of life. In one tiny patch of about 3 square centimetres there were no less than 5 adult Athous haemorrhoidalis, a common beetle whose larvae feed on tree roots. I also watched my first Spotted Flycatcher of the year flycatching from the mighty limbs of a particularly grand Beech tree.

We carried on down the road, checking every beech clump on the left side of the road to see if we could spot the easily-missed orchids. Surely we were supposed to be looking on the left side of the road? My dad agreed and we continued, starting to lose hope. We soon reached a point which was surely much farther than the directions had intended. Where were they? We must have missed them. We gloomily trod back up to the car, disappointed that we hadn’t seen these special plants. My eyes drifted over to the side of the road we hadn’t been looking at, where I stopped suddenly. I stood staring at two beige plants with disbelief. We had found the two Bird’s-nest Orchids! They were looking exactly as they had in the photo on the latest sightings page on the SBRS website which was taken 8 days before. Here are some photos and a very short mini-documentary:

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