An assorted bag

We are clearly sinking down into autumn: temperatures are dropping and there are signs of an annual wind-down wherever we look. One of the most obvious signs is the large number of caterpillars that can be seen wandering out in the open, rather than feeding in hidden places. This is due to them seeking a pupation place where they will make a cocoon that they will remain in during the winter before emerging as adults next year. This is the normal overwintering strategy for most of our insects, since it makes sense to have a cosy wrapper during the coldest part of the year. That is not to say that this is the only strategy: some species overwinter as eggs, others as adults - some hibernating, others being active during only this part of the year. Different strategies have different benefits: those species that are active during the winter must put up with the colder temperatures, but there is less competition for food and there are fewer predators around.

Recent caterpillar sightings include:

The Small Tortoiseshell butterfly, on a patch of nettles which I allow to grow near the chicken run:

Larva of Small Tortoiseshell butterfly

And the Flame Shoulder moth, which feeds on Dock and Dandelion:

Larva of Flame Shoulder moth

It should be noted that there are two distinctly different colour versions of this larva: the other version is brown.

This is also a good time to have a look at lichens: some of the vegetation and leaves that hide them are beginning to die back. This is the rather scarce lichen, Pannaria rubiginosa:

Pannaria rubiginosa on Oak

Pannaria rubiginosa is an indicator of extremely clean air, growing only in the west of the country. It's said to grow on various deciduous trees, but I have only ever found it on Oak. The red objects are the purely fungal fruit-bodies which eject spores for wind-dispersal, and the coppery filaments at the top and bottom of the image are the very common liverwort Frullania tamarisci. F. tamarisci is, again, a mainly western species.

I had an idea that the sunny spell at the weekend might be one of the last for a while, so I dashed out to see what I could see. There were many hoverflies still flying, and I got a decent shot of Helophilus pendulus, along with an unidentified muscid:

The hoverfly Helophilus pendulus (top)

And also a late shot of the solitary bee Halictus rubicundus:

The solitary bee Halictus rubicundus

I should actually use the term 'solitary bee' with some restraint in this instance: Halictus rubicundus is usually solitary, with each female making her own tunnel for her own eggs, but there is evidence that this bee can actually operate in a pseudo-social manner, with some females acting as pseudo-queens in aggregated colonies. This behaviour might show an evolutionary link between solitary bees and social bees, or perhaps we're seeing a change in behaviour from solitary to social in a particular species (or maybe even the reverse!)

New to my Species Index.

I found a snippet of information last week that put a completely new slant on how I understand the relationship between host and parasite/predator. In the normal circumstance, a predator or parasite cannot be present if its host is not present: the host must always precede the predator. This is simply because the predator must feed, and cannot exist in the absence of its food source. So the normal course of events is that a species arrives, perhaps through warming, or perhaps through human intervention, and survives in the absence of its parasite(s). That's one reason why invasive plants can survive so successfully: their native parasites and predators have not yet arrived. Eventually, through accident or, again, through human intervention, parasites and predators turn up and begin to keep numbers in check: a few weeks ago I posted images of a new leaf-miner on Himalayan Balsam. Another new(ish) leafminer - Cameraria ohridella - that mines Horse Chestnut leaves arrived in England from the continent a few years ago, and has been spreading northwards at quite a rate. The damage to infected trees can be quite severe, and it seemed that unless its native parasite(s) turned up to keep a check on its numbers, some of our trees might be threatened. But this year it was noticed that infections were less severe than in previous years. Despite extensive checking, however, no specimens of any specific parasite could be found. Then we began to get reports that people had seen Blue Tits and Great Tits feeding on the larvae and pupae of the miner: it seems that they have learned about this new food source that they had previously been ignoring. This adds a new dimension to my understanding of parasite/predator/host interactions: in cases where the predator is not an obligate feeder on a host (Tits can eat many other insects), the predator can pre-exist the host and only becomes a predator once it realises that it can be a predator of the host. Fascinating.

Lichens and leaves

Just when I thought the season couldn't get any more odd, I spotted a Willow making new leaves on a couple of shoots:

New Willow leaves

This is the same Willow specimen that has the opening catkins on it, so it has obviously been thoroughly confused: the leaves on this specimen of Willow normally appear after the catkins, rather than at the same time. I have received reports that Daffodils are making good growth in a nearby location, so something odd is happening.

This is a good time of year to have a look at lichens. Although they are present all year round, they are often hidden by leaves and plants, so they are now more visible and accessible.

Lichens are a combination of a fungus and a photosynthetic partner. They are usually described as a symbiotic relationship between the fungus and either an alga or a cyanobacterium, but I see it more as a boss-victim relationship for reasons that I have previously explained numerous times. Either way, lichens can be found in wildly varying shapes and colours and are very important as pioneer species, converting wood and rock into soil over time.

There are several reproductive strategies used by lichens: some create fruit bodies which are purely fungal, and eject spores into the atmosphere in the hope that they will land on a nearby victim in order to create a new specimen. Others create little packages of fungal material combined with trapped algae which are ejected as 'starter packs' of lichens ready to go. Still others grow on fragile material such as soil and simply fracture into a new specimen.

Some lichens use more than one of these reproductive techniques, and can therefore be found in different states, depending on which strategy they have currently chosen. This specimen of Hypotrachyna(Parmelia) revoluta is very unusual, in that it has produced purely fungal fruitbodies. One is visible just to left of centre:

Hypotrachyna(Parmelia) revoluta with fruitbody (orange)

Hypotrachyna revoluta is very much a western species and can be found mostly on wood, but sometimes on rock. New to my Species list.

Ramalina calicaris, on the other hand, regularly produces fruitbodies, and they can be seen here as little cups on the tips of most of the branches:

Ramalina calicaris

The orange material to the lower left and upper right of the branch is the alga Trentepohlia, which is one of the victims of choice used as part of many lichens. It is no coincidence that Trentepohlia and lichens are often found in the same location, since the lichen has probably formed principally due to the prior existence of the alga in that precise location.

Evernia prunastri is readily identified by the bifurcating branches, which make it look like antlers:

Evernia prunastri

The upper surface can be grey or green, but the underside (shown) is almost white.

Platismatia glauca is another new species for me. It is usually found on the upper side of horizontal branches:

Platismatia glauca

New to my Species list

Lecanora chlarotera is a very common lichen on Willows. I think there are few trees without some of this somewhere on the trunk:

Lecanora chlarotera

I love the colour of those fertile fruitbodies, somewhere between olive and brown. Notice how straight the line of fruitbodies is on that sample. I have a strong suspicion that these lichens are spread by slugs, perhaps even after the spores have passed through them and been left in the trail they leave behind.

Peltigera sp. lichens have very leafy structures and can grow very large. This specimen has been tentatively identified as Peltigera lactucifolia, but the orange fruitbodies seem to be the wrong shape (round, rather than elongate). Research ongoing by the good and great, but I think it's actually Peltigera horizontalis.

Peltigera cf. lactucifolia

Pannaria rubiginosa is a very attractive lichen with a distinctive appearance:

Pannaria rubiginosa

The victim in this case is the cyanobacterium Nostoc, which can often be found as a green/brown jelly on paths and carpark surfaces.

That's another two species for my species list, which must be nearing a total of 1450. I'll update it before the year runs out.