Monday, 30 September 2013

Brighton Break

Elms in a Brighton street. 27 September 2013
In a word association game, anyone given the word 'Brighton' will inevitably respond with 'elms'. No? Well, they should. The first photograph shows a rather mundane street in Brighton but the roadside trees are elm. Anywhere else in Britain this would be a most unusual sight but in Brighton there are thousands of such trees - over 17,000 at the last count. 
A 'Weeping Elm' near to the Royal Pavilion.
26 September, 2013

Elsewhere in the town there are finer examples, some even being rather famous. The next example, a specimen of Ulmus glabra 'Horizontalis' was photographed in a park adjacent to the Brighton Royal Pavilion. It might be assumed that these trees are naturally resistant to Elm Disease but in fact their survival is due to a very well organised 'sanitation' program which quickly identifies, and deals with, any outbreak of the disease. As most people
are aware the disease is caused 
by a fungus carried by the beetles, Scolymus scolymus and Scolymus multistriatus. 

No doubt I am a philistine, but I found this park far more interesting than the Royal Pavilion. Of course there were the usual street pigeons (feral Rock Doves) and Wood Pigeons strutting around but, staying aloof from these, was a Stock Dove. This is a slightly less common species, perhaps often overlooked,  and lacking any of the bold markings borne by its relatives.

Stock Dove in the gardens adjacent to the Royal
Pavilion, Brighton. 26 September, 2013

A calliphorid fly, Stomorhina lunata, taken in gardens
beside the Royal Pavilion, Brighton.
26 September, 2013
I was stooping down to take a closer look at this bird when I spotted a rather unusual fly on nearby foliage. Fortunately (but not for the fly) I managed to catch it and, once home,  was able to identify it as Stomorhina lunata. This relative of the blowflies is described in Peter Chandler's Checklist as an "occasional vagrant". It is more at home in southern Europe where it apparently feeds on locust eggs. There are yellow bars on the abdomen, rather like some hoverfly species, and there is striping on the eyes reminiscent of certain Horse Flies. Is it established in southern England? If it is breeding here it may feed on grasshopper eggs, after all a locust is really a large grasshopper. 

Another insect to catch the eye was the familiar Green Shieldbug, Palomena prasina.
Although it is bright green throughout the summer months, it takes on dull brown colours to overwinter. The specimen I photographed was in a transitional stage; it will eventually hide itself away under dead leaves or some such material and remain concealed until spring.
Green Shieldbug, Palomena prasina, in the gardens
of the Royal Pavilion, Brighton 26 September, 2013

Indian Pokeberry, flowers.
Gardens beside Royal Pavilion, Brighton

By and large the park was planted up with commonplace species but I was pleased to see a few plants of Indian Pokeweed, Phytolacca acinosa in the flower beds. This species is frequently bird-sown and the fact that the plants weren't labelled suggested that they weren't a deliberate planting. 

Indian Pokeberry , Phytolacca acinosa ,in fruit.
Brighton, 26 September, 2013
Although birds eat the berries with impunity they are poisonous to humans unless carefully cooked. It has a long flowering season; some flowers were yet to open but elsewhere there were fully ripened fruits.   

I could have spent more time in these gardens, and many people less strong-willed than myself would have lingered on to give more attention to the fungus, Melampsora hypericorum affecting the leaves of a St John's Wort. 
Hypericum rust, Melampsora hypericorum,
affecting St John's Wort. Brighton, 26 September, 2013

...but there were other places to visit and other scenes to enjoy and I tore myself away. 

Tuesday, 24 September 2013

Lepidoptera: obvious - and less so

Lepidoptera - butterflies and moths - are familiar to us all from early childhood. We soon recognise butterflies, such as the Comma, as they tend to be colourful and diurnal; moths are often duller and nocturnal. In fact many 
Comma, Polygonia c-album, on Buddleia
Byfield, 24 September, 2013
moths are also diurnal but there is another problem: many moths are small - and some are very small indeed. For this reason many are referred to as micro-moths. They are abundant in most habitats but obviously they are easily overlooked. Fortunately their presence may often be revealed by other clues - leaf mines. These are created by the tiny larvae as they munch their way through a leaf between the upper and lower surfaces. Often the mines are obvious, but in some cases they can easily be missed. A case in point is that created by the Poplar Bent-wing, Phyllocnistis unipunctella. It looks rather like a faint snail trail across the leaf, in this instance a Lombardy Poplar beside the playing fields in Byfield. Luckily the bright sunlight helped me to spot it.                       

Mine formed by the larva of the Poplar Bent-wing,
a tiny moth, Byfield, 23 September, 2013

A rather different form of mine is that of the Hornbeam Midget, Phyllonorycter tenerella. The Hornbeam is not a native tree in Northants but is widely planted, and this tiny moth has increased its range as a result of these plantings.

Mine of the Hornbeam Midget, Phyllonorycter tenerella
Byfield playing fields, 23 September, 2013

I am confident that all my readers - both of them - will now go dashing out to seek these fascinating mines. A word of caution is therefore called for: moths are not the only insects to exploit this leafy niche. Numerous two-winged flies also create very similar mines and the final photograph shows the mine of an agromyzid fly, Ophiomyia beckeri. This is a widespread species but I am not aware of any other records of it from Northamptonshire.

Leaf mine on sow-thistle made by the larva of a fly,
Ophiomyia beckeri. Byfield. 10 September, 2013

In my next blog I'll try to be less self-indulgent and write about something interesting!

Monday, 16 September 2013

Mud, mud, glorious mud

Adjacent to my friend Harry Ferminger's house is a pond with a surface area of around 500 square metres (Does that make it a small lake?). I asked Harry who owns it. He said that he wasn't sure but didn't think it was his! 

Anyway, yesterday I decided to have a stroll round it and so, sweep net poised, I gave it a recce. The first thing to catch my attention were the waterside plants. Cattle regularly visit the pond/lake to drink and their trampling has created a very interesting uliginous environment with Celery-leaved Buttercup (Ranunculus scleratus), Red Goosefoot (Chenopodium rubrum) and Marsh Cudweed (Gnaphalium uliginosum) present. None of these is rare but, with the loss of this kind of habitat, all are far less common than was once the case.

Marsh Cudweed beside pond near Byfield.
16 September, 2013 
No one would regard Marsh Cudweed as a spectacular plant and, with its small, brown, petal-free flowers it is hard to accept that it is in the same family - Asteraceae - as Dahlias and Marigolds.

Celery-leaved Buttercup beside pond.
Byfield, 16 September, 2013
The Celery-leaved Buttercup is also a disappointment for those familiar with its larger flowered relatives. It is a plant demanding close inspection to appreciate its features. It also required me to kneel in mud to get a decent photograph and I drew the line at that. 

A closer view of the same plant.

As a child I was familiar with this little buttercup at Kingsthorpe Mill and elsewhere. I rarely see it nowadays so I was delighted to make its acquaintance once again.

Red Goosefoot is another frankly dull plant. It is probably most often to be seen on manure heaps, and many people would probably argue that it is an appropriate habitat for this member of the Amaranth Family, Amaranthaceae. Until recently it was always placed in the Spinach Family, Chenopodiaceae, but times are a-changing. The pondside mud in which it was flourishing was probably enriched with cattle droppings so, although the plant is edible ("a delicious addition to salads", claims one website) I didn't exactly salivate and the plants remain where I found them.

Saturday, 14 September 2013

Shaggy Bracket Fungus

Ash tree in Oliver Tynan's garden
Byfield, 10 September, 2013
My friend Oliver Tynan has a lovely garden. One of the most attractive features is a small pool, permanently fed by a spring. It is overhung by a very large ash tree which, when I looked at it a few days ago, presented a quite remarkable sight, for a bracket fungus which has attacked it was shedding rust coloured spores in vast numbers. Millions (billions?) of them were staining the trunk of the tree and surrounding vegetation. Perhaps normally these are quickly washed away or dispersed on the wind, but the weather has been very dry recently and the tree is in a sheltered spot, subject only to light breezes.

The fungus involved appears to be Shaggy Bracket, Inonotus hispidus, a widespread and fairly common species whose target is normally ash but will occasionally attack oak and other broad-leaf trees. 
A closer view shows how nearby ivy leaves  have been dusted with spores, as had herbaceous plants and grasses nearby.

A closer view of the tree showing the concentric
rings on the fungus which help to identify it.

Like most (all?) bracket fungi, Inonotus hispidus is a pathogen and so will lead to the death of the tree. It is an unfortunate fact that local authorities and land owners generally feel obliged to cut down these diseased trees, and where a falling branch could be a hazard this is understandable. But if the tree can be allowed to decay and fall it will be of enormous value to a great range of creatures for whom the timber is a vital resource.

Incidentally Chris and I were on the bus returning from Banbury yesterday when substantial branch of rotten wood fell on to the bus with a startling thump. The driver was forced to pull in to the roadside and check his vehicle. Nothing vital had been damaged but the roof had a significant dent. Had the branch fallen on to a small vehicle it would have been serious, almost certainly resulting in injuries.

Friday, 13 September 2013

Byfield Pool

I suppose I make two or three visits to Byfield Pool each year. It is a nature reserve of the county Wildlife Trust but gets very little publicity and very few visits from recorders other than myself, probably because it is fairly small, rather remote and appears to have no great rarities. Nevertheless it is well worth visiting and I never fail to note something of interest - or at least, something of interest to me.

Bramble leaf mined by Stigmella splendidissimella.
Byfield Pool, 12 September, 2013
By this time of the year plants have accumulated a great variety of galls and leaf mines. This bramble leaf shown has been mined by the larva of a micro-moth Stigmella splendidissimella. It is no wonder that people often prefer to use an English name, which in this case is the False Bramble Pigmy Moth. It is very common and widespread. A close-up shows more detail and it can be seen that the larva has eaten its way between the upper and lower surfaces of the leaf, with the mine gradually widening as it grows. It comes to an abrupt end where the larva leaves the leaf.

So many creatures had been nibbling, mining or galling hawthorn leaves that it will require a dedicated visit to deal with them. We take hawthorns for granted but, in one way or another they support a huge range of creatures, from deer which browse the foliage down to tiny flies, micro-moths and ichneumons. Sometimes, however, they grab our attention. 

Hawthorn in fruit near Byfield Pool
12 September, 2013

As I left the reserve I was struck by the beauty of hawthorn branches, made pendulous by the weight of their fruit. A close look showed that the specimen was not Common Hawthorn but the less common Midland Hawthorn, Crataegus laevigata. Perhaps the fruit on this species ripen earlier than its familiar relative. The two species may be identified from the shape of their leaves, shown on my blog "Ne'er cast a clout" from 15 May.

Thursday, 12 September 2013

Its Tegenaria time again

It is evening in the late summer or early autumn and you are just settling down to watch some television when, out of the corner of your eye, you see a rather large, dark, long-legged spider dash across the room. It will be a Tegenaria species and, if you live in south-east England or the midlands it will almost certainly be Tegenaria gigantea. It will usually prove to be a male, out in search of a female or - to use the correct biological term - it is out "on the pull". In their wanderings these spiders will often end up in the bath or a sink from which, thanks to the smooth sides, they cannot escape. Today a fine specimen was in our kitchen sink. The long legs suggested immediately that it was a male; the swollen palps (the short leg-like structures at the front end) were swollen, confirming its gender.
Tegenaria gigantea in our kitchen.
Byfield 9 September, 2013

Under the microscope it will be seen that this swollen area is a very complex organ. It is a secondary sexual structure, the palps being used to introduce sperm into the female via an equally complex structure, the opening to which is known as the epigyne. The complexity of these organs, unique to each species, means that hybrids are very rare, since the swollen end of the male palp (the tarsus) must fit the epigyne with precision, rather like a key and keyhole. The epigyne is situated beneath the female's abdomen so it goes without saying that the insertion of the palp into the epigyne is a hazardous business for the male, and groups of males will meet in mid-summer for training days(Tony, stop it. You have been warned about frivolity on previous occasions.) 

I have referred to this species as Tegenaria gigantea, but in fact it is probably Tegenaria duellica. It was thus named by the French arachnologist Eugene Simon but the specimens he examined (the type-specimens) have never, as far as I am aware, been located so we cannot be sure in this matter. For this reason the later name of Tegenaria gigantea is frequently used, as these type-specimens are known and available for examination.

Several other Tegenaria species occur in Britain, one of the most interesting being Tegenaria parietina. Males of this species are particularly long-legged and, if you suffer from arachnophobia, very scary. Its common name is the Cardinal Spider, so-called because Cardinal Wolsey was apparently terrified by this species when residing at Hampton Court. It is now a scarce spider, generally confined to old buildings, and I have never found a specimen, although a contact once sent me some sent some from sacks of potatoes which had just been unloaded from the hold of a ship.

Monday, 9 September 2013

Ragwort and its visitors

I have had few opportunities to examine any plants of Common Ragwort (Senecio jacobaea) recently. They seem to have been a little less frequent this year and, if so, farmers will be pleased. As I may have written elsewhere, the plant contains powerful alkaloids, notably jacobine, and is poisonous to stock, although an animal would have to consume a huge quantity for a fatality to occur.

Ragwort, Senecio jacobaea, Solden Hill, Byfield
It is quite handsome in a rather untidy way and its nectar and pollen attract large numbers of insects. You could say that the plant is a typical Senecio but in truth it is a huge genus whose members take on many forms from cactus-like succulents to large shrubs. In reality there is no typical Senecio.

One insect with an unbreakable association with these plants is the Cinnabar Moth (Tyria jacobaeae) This is a familiar day-flying moth, unmistakable with its bold black and red wings. These wings are a warning to would-be predators. and any creature which attacks the butterfly will not quickly do so again. The same is true of the caterpillar. These feed on the Ragwort and store the poisonous alkaloids in its body. These remain stored throughout the metamorphosis and are therefore still present in the imago. Again the colours - this time yellow and black stripes - serve as a warning.

The larva of the Cinnabar Moth. Solden Hill.
When I was examining plants on Solden Hill I was struck by the number of insects being attracted to the flowers. Notable among these was the tachinid fly, Eriothrix rufomaculata. To the non-specialist the tachinids can seen rather nondescript flies but some are very distinctive and this Eriothrix species is one of the first that the newcomer learns to recognise. The specific name 'rufomaculata' means 'red-spotted' and the fly has clear reddish patches on the sides of the abdomen.

Eriothris rufomaculata on Ragwort. Solden Hill.

Tachinid flies are all parasitoids. These use various techniques by which their larvae gain access to a host - generally another insect - and then begin to feed on the unfortunate victim, usually resulting in its death. 

In the case of Eriothrix rufomaculata the host is not known with certainty, a remarkable situation for such a common insect.