In early June, Ed Baker, a specialist in aphids, came to Dundreggan for a week, to carry out a survey for us there. I’ve had a growing interest in aphids for the last year or so, and I was very pleased when Ed had responded positively to my invitation to do a survey for us. He’d also been very helpful in identifying aphid specimens I’d sent to him over the past couple of months, and I’d been looking forward to joining him for a couple of days during his survey.
I was able to spend part of 3 days with Ed during his week at Dundreggan, and as with the visits from other specialist surveyors, it was a great opportunity for me to substantially increase my knowledge about aphids. I also learned to identify various aphid species, and perhaps most interestingly of all, I gained a lot of understanding about the fascinating relationships aphids have with some of their host plants, and the parasites that prey on them.
I’d previously seen some aphids on a sycamore tree (Acer pseudoplatanus) that’s growing in the garden outside the lodge at Dundreggan, so we had a look at those first. The underside of the leaves were covered in aphids, the majority of which were a species called Periphyllus acericola. There were so many aphids, sucking sap from the leaves and excreting a clear liquid called honeydew, that the leaves were covered on their upper sides by this sticky liquid that had dropped from the aphids on leaves higher up.
While we were looking at the aphids, I noticed a couple of other invertebrates on some of the sycamore leaves as well. One of these was the distinctive cucumber spider (Arienella cucurbitina), which I wrote a blog about last year, when I saw some wood ants attempting to steal the egg sac of one individual. On another leaf there was a mining bee (Andrena sp.), a relative of the rare mining bee (Andrena marginata) that’s been found on Dundreggan. I didn’t collect this individual, and as it’s not possible to identify it to species level from photographs, it will remain just identified to the genus Andrena. It’s not the rare species though, as that one is only active in late summer when its food plant, devilsbit scabious (Succisa pratensis) is in flower.
Before we left the garden by the lodge we looked on some other non-native trees growing there, and we found some aphids on a Norway maple (Acer platanoides). These were a relative (Periphyllus lyropictus) of the first ones we’d seen on the sycamore tree, and like those, there were both adult aphids and immature individuals, called nymphs, feeding together on the underside of the leaves.
Leaving the garden, we walked up into the woodland nearby and headed for some aspen trees where I’ve seen some aphids in the past couple of years. I’ve previously photographed one species (Pterocomma tremulae) that was feeding on the stems of young aspen suckers and being tended by wood ants (Formica lugubris). However, I’d also seen some other aphids feeding on aspen leaves, and Ed told me these were another genus (Chaitophorus), but he wasn’t able to determine the species until he could look at them under a microscope.
On a different aspen tree about 150 metres away, we saw an unusual formation of aspen leaves, where the leaves were all drooping downwards forming a tent-like structure known as a leaf nest. This is the work of another aphid species (Pachypappa tremulae), and inside the leaf nest there were a lot of these aphids, covered in white wax. The aphids suck the sap from one side of the petiole, or stem, of the leaf, and this causes each leaf to bend down, thereby creating the leaf nest.
This a protective mechanism, that enables the aphids to feed inside the nest, unseen by predators and parasites. The wax that these aphids secrete is a defensive compound, making them unpleasant and very sticky for any predators that attempt to eat them. This makes the individual aphids look very untidy, and I imagine it must be hard for them to move around easily, encumbered with all this wax!
When there’s a group of these aphids clustered together, covered in wax, it looks like a chaotic mess, and perhaps that’s also deliberate, as a strategy to confuse the aphids’ predators and parasites.
Near this aspen tree, there was a nest of wood ants (Formica lugubris) right at the base of a juniper bush (Juniperus communis), and while I was photographing the aphids on the aspen, Ed had a close look at the juniper.
There were aphids (Cinara juniperi) feeding on it, and although there were ants on the juniper, they didn’t seem to be tending the aphids, the way they do with some other aphid species on different trees. Ed thought they may just be collecting the aphids’ honeydew, and he also noticed some bumblebees foraging around the juniper – again he thought they might be foraging for the honeydew that the aphids produce as a waste product.
As we looked at the ant nest, we spotted the ants dragging something bright across the surface of it. Having a closer look, I realised it was the head of a dragonfly, with its very large compound eyes visible. Colin Hall, one of my colleagues at Trees for Life who has a keen interest in dragonflies, later identified it as being the head of a northern emerald dragonfly (Somatochlora arctica).
Over the years, I’ve watched wood ants dragging many insects back to their nests, but I’d never seen them with part of a large dragonfly before. I wondered how the ants had come to catch this prey – had they found the dragonfly already dead and simply dismembered it? Or had they come across it when it was newly emerged from its chrysalis and not yet airborne, so they were able to overwhelm and kill it? There’s no way of knowing the answer, so it will have to remain as one of Nature’s mysteries…
From that juniper we headed back down hill and along the way we passed some old Scots pines (Pinus sylvestris). While Ed looked for aphids on them, my attention was drawn by the pattern of the bark on its trunk, particularly to an area where a section of bark had come loose, and was held at an angle, slightly out of place to where it had been. This illustrated very well the wonderful natural jigsaw puzzle-like pieces of the bark, and how they fit together in three dimensional layers, one on top of another.
We came down past the wild boar enclosure, and just outside it, next to the path, Ed spotted some aphids (Uroleucon sp.) on the flower stem of an autumn hawkbit plant (Leontodon autumnalis). He wasn’t able to identify them to species there and then, so he’ll let me know in due course which one they are, once he’s had a chance to key them out, using a microscope to examine the identifying features.
Nearby, on an eared willow bush (Salix aurita), we came across a large red damselfly (Pyrrhosoma nymphula). It was a male, and it must have been newly-emerged, as it was very bright and fresh-looking, and was just perching on the the bush, on this dull and cool day. On some bracken (Pteridium aquilinum) not far away, I found a brightly-coloured large click beetle that I was able to identify as being Ctenicera cuprea. The feathery antennae indicated that it was a male.
From there we crossed the road and spent some time in the riparian area, between the road and the River Moriston. This contains some different habitats and some plant species that don’t occur elsewhere on the estate, so Ed was hoping to find some different aphid species there. We looked on one eared willow bush (Salix aurita), and although we didn’t see any aphids, there were a few garden chafers (Phyllopertha horticola) – large beetles that are common in early summer.
Underneath one of the willows was a small patch of marsh marigolds (Caltha palustris), and Ed was happy to find some aphids (Rhopalosiphoninus calthae) on the leaves of one of the plants. This is a species that feeds only on marsh marigolds, and it was on a target list of species that he’d prepared before the survey, that he hoped to find on Dundreggan. By this time I was becoming somewhat overwhelmed by the specificity of the hosts that certain aphid species, such as this one, depend on!
This was reinforced when we found another aphid species (Aphis armata) on the stem of a foxglove (Digitalis purpurea) beside the driveway back to the lodge. This species is found on foxgloves that are typically growing poorly in difficult conditions, and sure enough this plant looked stressed, and was not in good condition – perhaps because of the marginal site it was growing on.
Just beside the foxglove plant, there’s an oak tree growing beside the driveway. We had a look at the leaves on that, and Ed found two different species of aphids feeding on their undersides.
One of these (Tuberculatus annulatus) is quite a common species, and Ed found it on several oaks on Dundreggan.
The other species (Thelaxes dryophila) was just found on this one tree there, and it is noted for the fact that these aphids tend to feed along the central vein of the leaf they are on. By now it was the end of the day, so we stopped then. However, I had another opportunity to spend time with Ed later on during the week of his survey, and I’ll continue this story in the next blog …