Wednesday, 28 November 2012


Each year, species come and go with the seasons: in spring we have the early flowers, such as Snowdrops and Primroses. In summer we see a wide profusion of insect life, and in autumn we find fruits and fungi. On this grand scale things are pretty much set: we won't find many butterflies in mid-winter and few fungi are seen in spring. But within this fixed schedule there is much fine-tuning: each year has different weather, leading to different temperature and humidity on any particular day in different years. This difference can cause annual variations in flowering and emergence dates, so although the general trend is predictable, the precise dates of first (or last) sightings are not: each year is different. Within this variable environment, however, all is not random: we have synchronisation to consider. Synchronisation is a fundamental driving force in our wildlife: when there is a strict dependency between two (or more!) species, they must be together at the correct time. For example, if a larva eats the leaves of a particular plant, then the larva needs to hatch when the leaves are available. The larvae of many moths and butterflies fit into that category. This synchronisation can be quite 'soft' - a few days won't make much difference to availability of the correct food - but other species need a much tighter synchronisation. If a parasitic wasp lays its eggs into the larvae of flies that eat particular fungi, then:

  • the fungus needs to be in place
  • the fly needs to have laid its eggs in the fungus and 
  • the larva must be nearing full size.

Considering that the life of a particular mushroom specimen can be as short as a few days, we can see that the synchronisation required for this parasitic wasp to be successful is extremely tight: its annual opportunity is measured in hours.

So what governs this synchronisation? On the grand scale, we have the year: the amount of time it takes for our planet to go once round the sun. Most lifecycles are governed by this unit of measure. Then we have the day: the amount of time it takes the planet to turn once on its axis. These units of measure are absolutely consistent (within the lifetime of our observations). But what is much more variable is day length. The shortest day is 21st December, with the longest being 21st June. The day length follows a sinusoidal curve between those dates and is the major indication of time of the year. If you know the day length, you know that it can only fall on two particular days of the year. And it's this dual identity that leads me on to the first of today's pictures.

In springtime, I expect to see Celandines and Willow catkins as the first signs that a new year has begun. Over the past few years, I have seen Celandines in late November. This is clearly the wrong time of year, since winter is just arriving: ice is imminent, which will cause flower damage and there will be no insects to help with pollination. But if you look at the 'proper' flowering time (February around here), you will see that the 'proper' flowering date and the 'wrong' flowering date are an equal distance from the shortest day: the day length is roughly the same in each case. So the plants have detected that the day length is correct, but have failed to notice that the overall trend of day length is decreasing rather than increasing. Something is causing confusion.

When I find the early Willow catkins, the first pollinators to be seen are queen bumblebees and early solitary bees such as Andrena clarkella. These bees need Willow pollen to get their annual nests started: their larvae will feed on this pollen, so the bees are stocking up from the only pollen supply that is available. (I should point out that Andrena clarkella is a prime example of synchronisation: the female gathers only Willow pollen, so she can be seen only during the Willow pollen season, which is around 60 days long. When it comes to the bumblebee, the synchronisation is tight for the queen, but more relaxed for the workers, since many flowering plants will be available when they hatch.)

I previously mentioned that I had seen a queen Bombus terrestris gathering pollen on two occasions recently, and wondered where her workers were going to get pollen over the winter. This weekend, I found out:

Willow catkins

Willow catkin opening
I have never seen Willow catkins opening before February, so this was a huge surprise. Queen Bombus terrestris have been known to make overwintering nests in the south of England, but I was still very surprised to make two sightings of a working queen this far north in late October and mid November. It appears that both the bumblebee and the Willow have been triggered by the same stimulus and have both synchronised at the wrong time. It will be interesting to see how this all develops.

Moving on to things at the 'right' time: now is a good time to look at mosses. Most mosses need microscopy to identify for the first time, but once the initial identification has been made, most species can be readily identified in the field. I spent some time photographing specimens on an old wall at the south of the town.

Homalothecium sericeum can be identified by the pale, pointed growing tips:

Homalothecium sericeum

Tortula muralis can be found growing on wall tops:

Tortula muralis (with Grimmia pulvinata in background)
The setae ('stalks' that hold up the capsules) catch the light very well. I'd love to think that they act as light pipes to drive sunlight deep into the base of the plant. I have previously covered the complex lifecycle of mosses, (here and here) but for now I'll point out that the setae and capsule are not wholly from the original plant, but are partly a junior generation that is parasitic on an older generation.

Most mosses have setae that carry capsules well clear of the parent plant in order to maximise the opportunities for spore dispersal. Grimmia pulvinata continues to puzzle me by its insistence on burying its capsules under the leaves of the parent plant:

Grimmia pulvinata showing 'drooped' capsules
Orthotrichum anomalum can be tricky to identify due to its extreme similarity to other mosses, and also due to a high degree of variability when wet or dry:
Orthotrichum anomalum
Growing on the same wall, I found:

The lichen Caloplaca flavescens, which normally dies away in the centre, although I think this specimen has had some assistance from molluscs:

Caloplaca flavescens
And Ivy-leaved Toadflax, which I think flowers here all-year round, now:

Ivy-leaved Toadflax

Just to add to the absurdity of the flowering Willow, here is a shot of Galerina clavata taken on the same day on my lawn:

Galerina clavata with frost

Monday, 19 November 2012

Smaller things

I was wondering how the queen bumblebee from October 28th was doing, and this morning we had a gap in the rain. Sure enough, at around 10 am, she was back at the Lavatera in the garden. (Well, I'm assuming it was the same one. Either we have two queens, each making a winter nest, or one queen working hard at getting her winter nest established. Either way, it's a notable observation.) I had hoped to follow her flight, but she went quite high and flew south so, sadly, her nest isn't all that close to me. It will be very interesting to see if we start to get B. terrestris workers in the next few weeks. Having said that, we had the first frost of the year last night. It was only a couple of degrees below, but a frost all the same. Here's a shot of the roof of my car:

Frost patterns

When the weather is on a bad run it's time to gather some samples and do some microscopy and deeper research.

There's a little mushroom that appears on my lawn several times a year. I know it's a Galerina, but today I decided to get it to species:

Galerina clavata
I put a specimen on a glass slide and waited overnight for a spore print. Here's the print on the slide waiting to be examined under the microscope:

Galerina spore print on the microscope
You can clearly see the brown spore print in that shot. (The blue column is the light shining up on the underside of the slide.)

We need to examine spores at a magnification of at least x400:

Galerina spores at x400

These spores are described as 'almond-shaped'.

I noted that the base of the stipe on the specimen was woolly white, so that makes it Galerina clavata, a common mushroom in association with mosses in lawns.

Liverworts are amongst our most overlooked plants. They are mostly tiny, and many could easily be assumed to be mosses. An in-situ shot would show nothing recognisable, so I took this shot (sample size about 3 cm. across) on paper in the study.

Liverwort sample about 3 cm. across
There doesn't seem much to work with there, but once you get a sample under the microscope, everything becomes clear. This sample is mounted on a slide ready for the microscope:

Liverwort sample on slide ready for microscopy
Note that the individual leaves have no central vein - a clear indication for a liverwort. There are no underleaves, and the leaves look to be entire, without lobes or teeth. Microscopy, however, reveals that the leaves are very slightly toothed - more so in the lower leaves - and that the teeth contain very few cells:

Cells in leaf tooth
All of this leads us to Plagiochila porelloides, which in this case is the predominant plant on the rear wall of the ditch where I found it.

I'm currently working on lichen microscopy. This is a specimen of Xanthoria parietina, an extremely common lichen that can be found on wood or stone and even on glass:

Xanthoria parietina
Lichens are an association between a fungus and a photobiont (either an alga or a cyanobacterium). Since the fungus is the only part of the organism that reproduces freely, I refuse to see this as symbiosis: I consider that the fungus (which needs the photobiont in order to survive) is virtually parasitic on the alga (which can and regularly does live happily on its own, without help from the fungus). This shot at x30 shows the circular cups which are the spore-producing, reproductive part of the fungus:

Fruit bodies of Xanthoria parietina

Friday, 9 November 2012

Brave new moth

Our moths have a wide range of breeding and overwintering strategies: some overwinter as eggs, others as larvae, still others as pupae and a few as adults. These patterns are largely governed by the availability of foodplants, but are also affected by the length of time that the larva takes to grow to full size. That latter aspect will be further complicated by the nutritional content of the food and the efficiency of conversion by the larva of leaf into flesh. Some larvae mature very quickly, giving rise to the possibility of multiple generations per year, but the majority of our moths have a single generation each year. This is quite convenient for those of us who try to identify moths: we can usually eliminate some possibilities due to the month when we find specimens but, again, there are complications. Heat clearly plays a part in this cycle, and some species are bivoltine (having two generations) in the south of the country but only one in the north, and as we are warming, the interface between the univoltine populations and bivoltine populations is slowly moving further north, so identification strategies are having to change over time. Add to that the fact that some previously univoltine species are now becoming bivoltine in the south of the country, you can see that we are constantly having to reconsider matters that were previously facts, but are now merely indications or simply wrong.

The Red-green Carpet has a cycle where the larvae feed on leaves of trees during the year and then pupate to emerge around now. The adults mate and the female goes on to overwinter, but the males die off. When the new leaves arrive in springtime, the female will come out of hibernation to lay her eggs and next year's single generation will be under way. So in this case we have the unusual 'seasons' where both adults are found from September to November, but with the female also being seen in March to May.

Given the very short breeding season, I suppose it's not all that surprising that this species will fly when others refuse to endure the rain or cold, and yesterday I found this specimen on a door-frame just as we arrived back from walking the dogs:

Red-green Carpet - Chloroclysta siterata
Red-green Carpet can usually be identified by the reddish streaks that run along the wing, but these are sometimes absent, and we have to rely on other features, such as the white 'chevron' near the trailing edge. The above example is a female.