- 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 catkin opening|
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.
Tortula muralis can be found growing on wall tops:
|Tortula muralis (with Grimmia pulvinata in background)|
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|
The lichen Caloplaca flavescens, which normally dies away in the centre, although I think this specimen has had some assistance from molluscs:
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|