This blog features some more of the remarkable diversity of species that I came across during my regular trips to Glen Affric in 2018, picking up from Part 1, which concluded with my visit there on the summer solstice in late June. My next trip to the glen was on 5th July, and I made four others that month as well, because summer is the time of maximum biological activity, and there are more species to be seen then than in any other season of the year.
As usual I stopped along the road between Badger Falls and Dog Falls, as that is where the greatest diversity of tree species is in the glen, and I’ve often found interesting invertebrates there as well. One of the first things I saw during my visit on 5th July was a very distinctive caterpillar on the underside of the leaf of a blackberry or bramble plant (Rubus fruticosus). Brightly coloured in red and black, with long hairs protruding from its body and a series of distinctive bristles sticking up, this is one of the most recognisable caterpillars in the country, and is the larval form of the vapourer moth (Orgyia antiqua).
Not far from there I came across a male fern (Dryopteris filix-mas) with some of its fronds twisted around in a circular fashion, instead of branching out straight from a main stem or stipe. This unusual structure is a gall that is induced by the larva of a fly (Chirosia betuleti), and it can be found on several ferns, including the broad buckler fern (Dryopteris dilatata) and the lady fern (Athyrium filix-femina). The characteristic shape of the gall is the result of the larva chewing on one side of the stem, causing the frond to curl in a circular direction.
Insects have developed many different techniques for feeding on the foliage of plants and the production of galls is one of the most interesting and unusual of these. Another method that is adopted by many organisms, particularly the caterpillars or larvae of some micro-moths, is that of leaf mining. An egg is deposited on the surface of a leaf by a female, and when the larva hatches out it feeds between the layers of cells that make up the leaf, creating a meandering passage across the leaf surface that is known as a mine.
The mine gets wider as the larva becomes larger, and the caterpillar leaves a distinctive dark line along its route of travel. This is comprised of frass, which is the waste material that caterpillars excrete. Each mine has its own unique shape, depending on the route taken by the larva as it travels within the leaf surfaces. Different species of caterpillars make different types of mines, thereby providing a fairly simple way to identify the species. Detailed information about this can be found on the British Leafminers website.
On my next visit to Glen Affric I began to notice quite a number of bright green spiders with red tips to their abdomens. These are known as cucumber spiders and are in the genus Araniella – there are two species commonly found in Scotland, which are difficult to tell apart. When I sent a few specimens to the arachnologist Edward Milner he identified them all as being Araniella cucurbitina. This one was a female guarding her egg mass on the underside of the leaf of a hazel tree (Corylus avellana). Spiders have strong maternal behaviour and having found this female on 11th July, I decided that I would check up on her during my subsequent trips to the glen.
There were many flying insects on the wing, and I stopped to look at the flowers of some angelica plants (Angelica sylvestris) growing on the roadside verge, where a lot of them had landed to feed. Angelica produces large hemispherical clusters of flowers that are known as umbels, and many insects are attracted by the flowers’ promise of nectar. In exchange they provide the service of pollination, and while this is often associated with bumblebees and hoverflies, there are many other insects, including beetles, two-winged flies and moths, that also function as pollinators.
There were quite a few different hoverflies feeding on the angelica flowers, but they were dwarfed in size by a strikingly-coloured beetle, the four-banded longhorn beetle (Leptura quadrifasciata). This is distinguished by its long antennae and the orange markings on its elytra, or wing cases. Like the other longhorn beetles, its larvae live in dead and decaying logs, where they feed on the wood itself, unlike the larvae of some other beetles, that feed on the fungi that decompose dead wood.
Beetle larvae that feed inside logs are relatively safe from predators but the larvae of insects that feed on leaves are much more vulnerable, especially to predation by insectivorous birds. To reduce the risks of this, various protective mechanisms have been developed, including that of leaf mining that I mentioned already. Another strategy consists of rolling leaves, so that the larvae inside them are not visible, and on a dog rose bush (Rosa canina) I found some good examples of this. A number of the leaves had been rolled by the larvae of a rose leaf-rolling sawfly (Blennocampa phyllocolpa), and they can feed inside the leaf roll, unseen by birds and other predators and parasites, such as parasitoid wasps.
On my next trip out to Glen Affric, on 15th July, I spent quite a long time with a young alder tree (Alnus glutinosa), observing and photographing all the different species that I found on it. I wrote a blog about this last year, but I also encountered some other interesting things that day. One of those was on the new growth of a young hazel tree, where I noticed a ladybird. Whilst many ladybirds have black spots on their red elytra or wing cases, this one, the cream-spot ladybird (Calvia 14-guttata), is readily distinguished by its off-white coloured spots.
Glen Affric is well-known for its diversity of dragonfly species, with at least 12 species recorded there, and as July is the best month to see many of them, I headed for a small lochan on the south side of Loch Affric where I knew there was a good chance of seeing some. By the time I reached the lochan however it had begun to rain, and there weren’t many dragonflies on the wing. By scouting around the edge of the water though I did spot an emerald damselfly (Lestes sponsa) resting on the needles of a young Scots pine (Pinus sylvestris), presumably waiting there until the rain stopped and conditions were better for it to take flight again.
The lochan itself was at its most beautiful as there were water lilies (Nymphaea alba) flowering around the edges, as well as numerous bogbean plants (Menyanthes trifoliata), all reflected in the still waters.
Here’s a short video clip of the waterlilies and bogbeans on the lochan:
My next visit to Affric was on 24th July, and I went back to check on the female cucumber spider (Araniella cucurbitina) that I’d seen guarding her egg mass on a hazel tree by Dog Falls on 11th July. She’d still been there when I looked for her on 15th July, and now 9 days later again, she was in virtually the same position, next to her eggs. Many people have a dislike of, or even a phobia of, spiders, but few know of their sometimes extraordinary maternal care for their young. This one had spent at least 13 days guarding her eggs, which is a significant time for a relatively short-lived creature such as a spider.
It seemed to be a day for spiders for me, as I found the nest of another spider on the underside of the leaf of an oak tree (Quercus petraea) in the glen. In fact, I found several of them on the undersides of different leaves on the same oak, and one of those was next to a couple of leaf mines. Those were different to the mines I’d seen earlier on the birch leaves, being blotch-shaped and only visible on the underside of the leaf. When I consulted with Rob Edmunds, one of the people behind the British Leafminers website I mentioned above, he said they were made by the caterpillars of a micro-moth in the genus Phyllonorycter, and they were possibly the species Phyllonorycter quercifoliella.
While the mines were interesting, I was more curious about the spider nest. I could see some movement within it, so I gently pulled the webbing apart to reveal what was inside: the mother spider and her babies, or spiderlings as they are known. There were dozens of these young ones inside the nest, with just a few, perhaps the more developed spiderlings, visible to me, next to their mother. While she was dark-coloured and almost black, the spiderlings were mostly translucent, with distinctive pale blue sections on their legs.
The contrast between mother and babies was quite remarkable, although I suspected it would not be long before the spiderlings darkened, to resemble their mother.
I was able to get the spiders identified thanks to the expertise of Edward Milner, a friend who is the spider recorder for Orkney and Shetland. The theme of procreation continued with my next discovery of the day, when I came across a pair of ticks (Ixodes ricinus) that were mating on the underside of a hazel leaf not far from the oak with the spiders. Ticks are in the same Class of organisms (the Arachnida) as spiders and scorpions, and have eight legs, no antennae or wings, thereby differentiating them from insects, which have six legs and antennae, and are winged. Ticks mate facing each other, with the male clasping on to the female. After mating the female goes on to feed and when fully engorged she lays up to 2,000 eggs.
Later in the day, and further west, near Loch Affric, I discovered some sawfly larvae feeding on the leaves of a young downy birch (Betula pubescens). I had never seen this species before, but I recognised them immediately as sawfly larvae, rather than moth caterpillars, because of the number of prolegs they had, and also due to the posture of their bodies. This latter involves a distinctive curved position, which was also displayed by the pine sawfly larvae that featured in part 1 of this blog. That evening a quick search on the Internet gave me the provisional identification of Croesus latipes for them, and this was subsequently confirmed when I contacted Andrew Halstead, a specialist in sawflies.
On my next trip to Glen Affric in early August, I went up to the Coille Ruigh na Cuileige exclosure, which is the site of Trees for Life’s first significant project – 50 hectares that were fenced off (in partnership with Forestry Commission Scotland) for natural regeneration in 1990. I’ve been photographing one particular Scots pine there since 1992, to document the growth of the young trees in the absence of overgrazing by red deer (Cervus elaphus), and it was time to take another in the sequence of images. While I was doing that I had a close look at the lower branches to see if there was anything of note on them, and on one I spotted a couple of wood ants amongst the needles. These drew my attention straightaway, as wood ants are often an indicator of the presence of aphids. They tend these sap-sucking insects and harvest the clear liquid known as honeydew that the aphids secrete as a waste product. Aphids are often very cryptic in their appearance, making them hard to find, so ants are very useful as they are larger and more mobile, making them much easier to see.
Sure enough, after a minute or two of searching I found a few brown aphids, feeding on the stem of the pine in between some needles. These were quite big in size for aphids so I suspected they were the large pine aphid (Cinara pinea), which I’d seen previously at Dundreggan, but had never found in Glen Affric before. Thanks to the help of the aphid specialist Bob Dransfield I was able to get this identification confirmed, and Hayley Wiswell identified the ants as the hairy wood ant (Formica lugubris). I was delighted with this discovery as it was not only the first time I’d recorded this aphid species in Affric, but also it involved the Champion pine that I’ve been monitoring since 1992. This was further proof about the success of the restoration work there, with this tree providing the habitat for two invertebrate species – the aphid and wood ant.
That day in early August was also notable for another reason. Not far from where the informal path leads up to the Coille Ruigh na Cuileige exclosure starts I stopped to look at some ragwort plants (Senecio jacobaea) that were flowering by the roadside. Ragwort is an important food plant for many invertebrates in late summer, and when I looked at this patch, there were a number of different hoverflies on them. I also spotted some small, triangular-shaped moths, which I took at first to be nettle tap (Anthophila fabriciana), which can often be seen on ragwort flowers.
However, when I got home that evening and compared the photographs I’d taken with others of the nettle tap moth I realised these moths were different. When I sent the photos to Roy Leverton, a lepidopterist who helps me with identifications, he replied saying the moth is a species known as the Inverness metal-mark (Choreutis diana), which has only ever been recorded from one site in the UK – Glen Affric. As far as I’m aware, there is no explanation for why this species hasn’t been recorded anywhere else – its larvae feed on birch leaves, which are plentiful and abundant throughout the Highlands. I was really delighted to have photographed the moth, given that it is unique to Affric, and when I looked for them again on my next two visits to the glen, there were still some of them on the same patch of ragwort plants.
In the years since it was protected in 1990, the Coille Ruigh na Cuileige fence has also enabled the growth of what is possibly the largest patch of creeping lady’s tresses (Goodyera repens) in the glen. This is an orchid that spreads by above ground runners, and is characteristic of Scotland’s native pinewoods, although it can also be found in pine plantations, including those of non-native pines. Early August is the best time to see this species, and there were indeed quite a lot of them in flower inside the exclosure, where they are protected from overgrazing by red deer.
On one of the orchids I noticed a tiny caterpillar on the topmost flower bud, which looked interesting, but unfortunately it was too young to be identified. When I sent the photo to Roy Leverton the best he could do was say that it was the larva of a moth in the Geometridae family. I was slightly disappointed by this, as I’d been hoping it could have been something interesting, such as a beetle I’d found on one of these orchids at Coille Ruigh na Cuileige in 2017. I’d sent that tiny beetle to Sholto Holsworth at the Natural History Museum in London, who identified it as being a species called Antherophagus pallens.
He said there are very few records for it in Scotland, and it is an interesting species that not much is known about. Members of the Antherophagus genus are apparently attracted to orchid flowers, as they know that bumblebees will come to pollinate them. The beetle larvae live in bumblebee nests, feeding on organic detritus, and the adult beetles cling on to the bumblebees with their mandibles when they come to the orchid flowers, in order to be transported to a nest. This behaviour, whereby one species uses another for transport from site to site, is known as phoresis, and in 2014 I wrote a blog about phoretic mites that were found on a sexton beetle at Dundreggan.
My next visit to the glen was in the middle of August and my first stop then was by the oak tree beside the bridge above Badger Falls. I’ve often found interesting invertebrates on this tree (including the Anyphaena accentuata and her spiderlings featured earlier in this blog), and this time was no exception, as I found a fungus growing out of the corpse of a dead spider on the underside of one of the leaves. Fungi that grow out of insects and spiders are known as entomophagous fungi (which means literally ‘invertebrate eating’), and I’ve been interested in them for some years. Unfortunately I haven’t been able to get this one identified yet, but Edward Milner did examine the spider and told me it was probably a ground-weaver spider (Lepthyphantes minutus), but it was too decomposed by the fungus to be completely sure.
On a Scots pine not far from there a distinctive-looking fly with large red eyes drew my attention, as it was sitting on some needles next to the buds at the tip of a branch. This was identified for me by Peter Chandler as being a female of a muscid fly species (Helina depuncta) which is quite widely distributed in England Wales, but for which there are relatively few records in Scotland.
There were a lot of insects on the wing, and I’m including a couple of butterflies I photographed nearby, even though they are quite common, and therefore hardly ‘unseen biodiversity’ in Glen Affric!
It was a day when I went to check up on some of the things I’d been following over the course of the past few weeks, including the cucumber spider on the hazel tree at Dog Falls that I’d first seen on 11th July. The spider was nowhere to be seen now (although she had been there on 24th July), but the egg mass was still there, and some tiny spiderlings were just visible, moving around inside it. I assumed that once the baby spiders had hatched out the mother had ended her long vigil over them, leaving them to their own devices.
I looked closely at the egg mass for a few minutes and was rewarded by seeing some of the spiderlings venturing outside the protection of the golden fibrous mass of the nest. They were quite different in colour to the adults – their bodies were mostly brown, with no green visible on them at this stage. Presumably as the spiderlings grow and moult they take on the adult coloration, although I suspected that most of these babies would not reach maturity, as a result of predation etc.
I also returned to the patch of ragwort, where I confirmed that some of the Inverness metal-mark moths (Choreutis diana) were still to be seen. Whilst there, I noticed another, larger moth that I recognised straightaway. It was the antler moth (Cerapteryx graminis), a species which has gained its common name from the distinctive white antler-shaped pattern on its wing. This one was a male, readily distinguished by its feathery antennae.
I regularly see this moth feeding on ragwort flowers in late summer, and they always seem totally immersed in their feeding, oblivious to my presence near them. They appear to feed for extended periods of time, and this one had pollen grains all over its proboscis, antennae and eyes. The antler moth is a member of the Noctuidae family, all of which are known to act as plant pollinators, and there’s no doubt that this one would be transferring pollen to the next ragwort flower it visited.
The other discovery I made that day involved one of my favourite groups of insects – the aphids. Although it’s not part of the Caledonian Forest ecosystem, gorse (Ulex europaeus) does occur in Glen Affric, mostly alongside tracks and roads, where the grit used to create the road bed provides an ideal habitat for it. I’d never really paid much attention to the gorse in the glen and in fact have organised Trees for Life work parties in the past to remove it, as it really shouldn’t be there.
I decided to have a close look at some of the gorse bushes, as I know they have aphids associated with them. Sure enough, after a few minutes I found some aphids (Aphis ulicis) on a bush, being tended by small black ants (Formica lemani).
This was another first for me in Glen Affric, as previously I’d only come across gorse aphids at Dundreggan, when the aphid specialists Bob Dransfield and Bob Brightwell were doing a survey there. They confirmed the identity of these aphids for me, and Hayley Wiswell kindly identified the ants as being Formica lemani, a smaller relative of the wood ants I’d seen tending the aphids on the Scots pine a few weeks before.
On another gorse bush a few metres away I came across more of the same gorse aphids, and there they were being tended by red ants. I recognised these as being in the genus Myrmica and Hayley identified them for me as Myrmica ruginodis, one of two common species of red ant that occur in the Highlands. In just a few minutes therefore I’d found two species of ants, the aphids themselves and the larvae of the midge (Aphidoletes aphidimyza) that preys on the aphids, on these two gorse bushes. It was a great example for me of how even a plant such as gorse that I normally pay little attention to can provide the habitat for a diverse range of species and the intimate ecological relationships that link them together.
This blog has become quite long, so I’ll continue with some more of the interesting biodiversity discoveries that I’ve made in Glen Affric in Part 3. To finish this one now though, here’s some video footage of the ants and aphids on the gorse bushes.