Webs of delight & fungal galls

Last weekend I went to Glen Affric again, camping there overnight. On Sunday morning it was very still, and there were perfect reflections in Loch Beinn a’Mheadhoin, with the mist adding a very special atmospheric quality to the scene. The trees and their reflections seemed almost to be hanging in mid-air, as there was nothing else visible to give a sense of perspective to the view.

There had been a very fine mist or dew during the night, and when I walked around I was immediately struck by the number of spider webs that were visible, with tiny dewdrops covering every strand. These webs were the work of a species of money spider (Linyphia triangularis) that spins its web close to the ground in a horizontal plane and then sits upside down underneath the web, waiting for insects to get caught in it.

Normally the webs are virtually invisible, but the morning dew revealed them in all their intricate beauty – a visual treat for us humans, but no doubt an unwelcome event for the spiders, as the dewdrops revealed the location of the webs, and may enable prey to avoid them. Most of the webs were in the grass along the roadside verge, but a few were on other plants, including a fern and a small eared willow (Salix aurita).

These webs are known as sheet webs, and are structurally different to the circular orb webs that are more commonly seen, such as those produced by the garden spider (Araneus diadematus). Looking around, I soon spotted one of those orb webs, with the spider sitting motionless in it, also covered in dew drops. With its web effectively revealed to the world, it seemed all the spider could do was wait patiently for the conditions to change.

And in fact, as it turned out, the conditions changed more quickly than I expected. At about 10 am, it began to rain, not very heavily, but enough to make me put away my camera equipment. When I returned to the place where the webs were a few minutes later, they were all invisible again. The raindrops had knocked off all the dew drops, and were themselves too large, and falling too fast, to adhere to the silk strands of the webs.

I was grateful for having been up early, so that I could see all the webs bejewelled with dew, although I daresay the spiders were much happier when the rain came, as they had a chance then to catch some breakfast in their webs.

Later in the day, I was walking in amongst some old Scots pines on the north shore of Loch Beinn a’Mheadhoin, when a moth fluttered to the ground in front of me. It was an autumnal moth (Epirrita autumnata), and newly emerged too, judging by how fresh its markings looked.

Nearby, a flash of bright red caught my eye amongst the vegetation on the forest floor. Looking closer, I saw a strangely coloured and distorted leaf on a cowberry plant (Vaccinium vitis-idaea). Although I’d never encountered this before I knew what it was – a gall caused by a fungus (Exobasidium vaccinii).

Remarkably, the fungus induces the plant to produce an abnormally-shaped leaf, in this case a red bowl-shaped growth which is much larger than the normal size of the leaf.

Once I was down at ground-level, I quickly spotted a number of other galls on cowberry plants around the first one – there seemed to be quite a well-defined zone where the cowberries were infected with the fungus. Some of the galls were larger, and all were white on the outside, contrasting with the bright red colour of the inner part of the bowl-shaped galls. The white areas are the parts that produce the fungal spores, enabling the fungus to reproduce and infect other cowberry plants.

I also saw one plant with what appeared to be a deformed and swollen bud on it, also pink in colour, and I wondered if this was another manifestation of the same fungal-induced gall. Searching the Internet back at home that night confirmed that this is the case – the galls caused by the fungus can take a number of forms.

I also noted that a closely-related species of fungus (Exobasidium myrtilli) induces galls on blaeberry (Vaccinium myrtillus). I haven’t seen that before either, so I’ll look out for it in future.

In amongst the infected cowberry plants, there were a few that seemed unaffected by the fungus, and some of those were flowering.

Cowberry has an extended season of flowering, and I’ve seen plants with flowers in November in previous years. At the end of another satisfying day in the Caledonian Forest, it was very good to see these flowers, particularly as most plants are getting ready for winter, and their flowering times are long past for another year.