London Natural History Society The place for wildlife in London

London Natural History Society - The place for wildlife in London

Geology image00Richmond Hill (gravel terrace). Looking from the river back to Richmond Hill; London Clay capped off by gravels from the Pleistocene Boyn Hill Gravel Member dating from about 400,000 years ago. Geology image05Blackheath pebble. From the c.50 million year old Blackheath Beds (Harwich Formation) marine gravels. Geology image06Horsenden Hill. Horsenden Hill (85m) looking across the London Basin to the North Downs on the horizon. Horsenden Hill is London Clay capped by the Claygate Member and Dollis Hill Gravel. The Dollis Hill Gravel is a Pleistocene river terrace deposit Geology image03Greenwich Park. Looking down from the Eocene Blackheath gravels down a slope to the Thames. The slope is comprised of several distinct stratigraphic layers. Geology image04Primrose Hill. Primrose Hill looking to the city. Primrose Hill (78m) is formed from 50 million year old Eocene London Clay bedrock, with no superficial deposits. Geology image01Below the man-made Pillow Mounds at High Beach, Epping Forest. The hill top is Quaternary Stanmore Gravel transported here by huge glacial rivers, sitting above much earlier Eocene Bagshot Sands laid down on the bed of a warm, shallow sea.

The geology of London, like the rest of Britain, is very complex. There are many different rock types visible at the surface, with some dating up to 145 million years ago, with many that are much more recent. The main bedrocks are Chalk and London Clay, with much of the surface geology made up of sands and gravels from the Eocene, till and gravel from glacial activity, and recent non-glacial deposits caused by wind or water action.

The London Basin area is formed from a layer of chalk accumulated on the bed of a warm sea in the Cretaceous period over 65 million years ago. Together with much of Southern Britain, at the same time the Alps were being formed around 15-20 million years ago, the area was folded to form a shallow basin (a syncline). This chalk basin is filled with other rock types, but it still surfaces today mainly in the Chiltern Hills to the north-west, and in the North Downs on the southern edge of the London area. At Westminster, it is 70 metres below ground. Chalk is porous, creating an artesian basin, and makes an alkaline soil.

Impermeable London Clay is also a sea-bed sediment, laid down 56-34 million years ago in the Eocene epoch. It lies on top of the chalk, and in some places is 150m thick. As with other clay soils, it is ‘heavy’ and not naturally good for agriculture, but two characteristics are very important for London: it is easy to be tunnelled and it makes very good bricks. Much of the London Underground system runs through tunnels dug into the London Clay, and this explains why there are few Underground lines south of the river: there is much less clay in this area. The classic yellow ‘London Stock’ brick is made from this clay, and can be seen in houses and buildings all over the capital.

Patches of other important sedimentary rocks that were laid down in the Paleogene period 65-25 million years ago include Thanet Sand, Woolwich Beds and Blackheath Beds associated with heathland and acid soils. The Bagshot Beds are old sands that lie above the clay, and create the hills of Harrow, Hampstead, Highgate and some of the heath around Esher.

The Ice Ages and more recent deposits

The Thames did not always follow its current path, but the action of great ice sheets eventually blocked the previous route through the Vale of St Albans and caused it to break through the chalk ridge at Goring from where it then scored its way through London, carrying much glacial debris with it. At the height of the last ice age as recently as 20,000 years ago, the ice sheet, extended down to present day Finchley, and deposited boulder clay around Finchley and much of London to the north. Repeated glacial and inter-glacial periods created much erosion and fluctuation in ice and river levels. The Thames alternately deposited and then cut through, gravel terraces formed.  Much of central London is built on these terraces, with extensive flat areas connected by quite steep inclines being very evident: the roads that lead from the Embankment to the Strand are connecting one terrace with another. Oxford Street is on the edge of a river terrace and St Martin's Lane slopes into Trafalgar Square past the National Portrait Gallery, moving from one terrace to the next lower one. These terraces form many of the heathlands and acid grasslands of London, including the area around Heathrow. Gravel extraction for construction has resulted in many gravel pits.

In several areas, these river gravel deposits are topped with Brickearth, a fine grained wind-borne sediment, used in brick making. The area around Pall Mall is one such deposit.

The many river valleys have deposits of recent Alluvium, and and still being formed today in some areas. Other rivers such as the Westbourne (through Hyde Park) and the Tyburn (Regent’s Park) have been lost underground in recent centuries, but have left their trace in Alluvium deposits on the surface, culminating in this case a large expanse of Alluvium at Westminster.

The soils formed from these surface geology produce a complex mosaic of different habitats, with their associated distinct flora and fauna.

Links

London Naturalist Geology Map: A map of the surface geology of the London Area, by Colin W. Plant (1994) (The London Naturalist 73: 215-220). Map here (as a .jpg file) or here (as a downloadable PDF version).

BGS Geology of Britain viewer

BGS iGeology smartphone app

The Hemiptera is a large and diverse insect order in Britain, containing nearly 2000 species, many of which can be found in London. In fact, some are found nowhere else! Species from continental Europe or even further afield are now regularly becoming established in Britain and the London area is often where they first appear. Now is an exciting time to record these insects within the capital.

Hemipteria Palomena prasinaCommon Green Shieldbug

Palomena prasina

A uniformly green species, although turning brown before hibernation. The membrane at the tip of the wings is dark. Very common in many habitats including parks and gardens, feeding on a wide range of plants.

Hemipteria1 Nezara viridulaSouthern Green Shieldbug

Nezara viridula

Similar to the above species and best distinguished by the transparent pale wing membrane. Uncommon and usually in man-made habitats. Most frequent in allotments, where it is particularly fond of runner beans. A recent arrival in Britain and largely confined to the London area. Records are of particular interest.

Hemipteria1 Rhaphigaster nebulosaMottled Shieldbug

Rhaphigaster nebulosa

This species is distinguished by the wing membrane, which is covered in dark spots. The antennae are also strongly banded. Uncommon and usually in man-made habitats. A recent arrival in Britain and so far entirely confined to the London area. Records are of particular interest.

Hemipteria1 Leptoglossus occidentalisWestern Conifer Seedbug

Leptoglossus occidentalis

A very large and striking bug, with characteristic leaf-like expansions on the hind legs. Native to the USA; a recent arrival in Britain and now widespread, although rarely seen in the summer months, when it lives on pines. Most records are of bugs overwintering inside buildings.

Hemipteria1 Corizus hyoscyami 

 

Corizus hyoscyami

A striking red and black bug which is also rather hairy. A recent arrival in the London area and historically confined to the southern and western coasts of Britain. Now found in a range of habitats including gardens.

Hemipteria1 Miris striatus 

Miris striatus

A large and distinctive black and yellow plant bug, most often seen in mid-summer. Widespread in parks and gardens on deciduous trees, particularly oaks and hawthorns.

Hemipteria1 Cercopis vulnerataRed and Black Froghopper

Cercopis vulnerata

An unmistakable species which is most often found in May and June. Widespread and common across much of England and Wales on a range of herbaceous plants, but rather uncommon in the LNHS recording area and largely absent from urban London.

Hemipteria1 Centrotus cornutusHorned Treehopper

Centrotus cornutus

An unmistakable species which is most often found in May and June. Widespread and common across much of England and Wales and generally associated with old woodlands. Rather uncommon in the LNHS recording area and largely absent from urban London.

Hemipteria1 Ledra auritaEared Leafhopper

Ledra aurita

The largest leafhopper in Europe, with characteristic ear-like projections on the thorax. A cryptic bark dweller, particularly on lichen-covered oaks. Rarely seen, although may come to moth traps.

Hemipteria1 Graphocephala fennahiRhododendron Leafhopper

Graphocephala fennahi

A very distinctive red and green leafhopper which feeds on Rhododendron and is frequent in London’s parks. Originally native to the USA, it was introduced to Britain in the early 1900s and has since spread widely.

The London Bat Atlas was initiated during 2010 with seed funding from the Vodafone ‘World of a Difference’ fund, which helped employ the services of Richard Law, to gather together the existing data holdings, as well as investigate the type of document and layout we wanted.

It took longer to accomplish than we originally thought, but with the help of Greenspace information for Greater London, our group has produced a document, which is as accurate as possible, but easy to access the information.

It is an example of the importance of submitting biological records, especially in this time of ‘blink and you miss it’ demolition and re-development. As always it exemplifies those boroughs where there are active bat group members so absence of records doesn’t mean absence of bat species!

There has been a lot of positive feedback since the Atlas was distributed especially from London’s remaining Biodiversity Officers, who have commented on its use as reference material, to support their requests for bat surveys, especially when responding to planning applications.

This article was first published in the Newsletter of the London Natural History Society, No. 240 February 2016

An excursion to this small nature reserve in west London was arranged jointly with London Wildlife Trust at fairly short notice, and was advertised not in the calendar but on the Society’s website and on the www.wildlondon.org website.

The day was a pleasant, mild, windless morning; over twenty adults, two teenagers and eight small children assembled at the LWT hut, several claiming they were ‘arachno-beginners’.

Some blue webs of Amaurobius sp. and the ‘spokes of a wheel’ web of Segestria senoculata were immediately pointed out on the hut itself. The group walked down the path into the reserve and soon found some large well-marked Garden Spiders (Araneus diadematus) on their orb webs, as well as some smaller Metellina segmentata web-spinners; both sexes of the latter were found sharing a web, as is often the case. There was some discussion of the difference between the sexes in spiders, and some members of the group were horrified to have it confirmed that after sex some female spiders kill and eat their mates, but were quietly amused to learn that in other species the low nutritive value of the males mean that she doesn’t bother.

One of the Metellina females was removed from its web and placed on a flat surface to demonstrate the weak back legs of these spiders which drag as they walk – characteristic of two families (Araneidae and Tetragnathidae) the females of which use their back legs for manipulating silk rather than to support their (heavy) abdomens.

Sweepnetting ivy-covered trunks of some of the birch trees produced specimens of the ‘buzzing spider’ Anyphaena accentuata (Anyphaenidae) with its characteristic ‘pair of inverted commas’ markings on the abdomen. Other characteristics were noted: they bear numerous particularly aggressive spines, and they are pale-coloured spiders with dark markings – unlike the blue-web spiders Amaurobius spp. which we found under dead logs, which are dark-coloured spiders with paler markings.

Among the ivy growing on the ground of the wood numerous sheet webs were seen, with the spiders hanging underneath the webs. These were the common money spider Linyphia triangularis.

Much of the reserve is secondary woodland dominated by birch and goat willow, many trees festooned with ivy, but there are a few open glades. In the largest of these we searched the grass for ground-living spiders and found several wolf spiders: Pardosa nigriceps with annulated legs, and at the edge of ‘the meadow’ a single specimen of the handsome Pardosa saltans a woodland wolf spider.

The meadow boasts several spectacular anthills but it was thought best not to disturb this fragile area of acid grassland – at a future date some pitfall-trapping might produce some interesting acid-grassland spiders.

Several mouse spiders (Clubionidae) were found outside the meadow itself but they proved to be juveniles; apart from adults of C. terrestris one of the commonest woodland species, none of the others could be identified with certainty. A single specimen of the small green spider Nigma walckenaeri was collected by sweepnetting, but its characteristic ‘sewn-leaf-webs’ were not seen.

The waterside vegetation around two small ponds produced juvenile specimens of Tetragnatha montana with their characteristic long legs and elongated abdomens. Under some birch logs at the far end of the reserve a large Tegenaria probably T. gigantea was seen on a big cobweb but it escaped into the brambles. Two large money spiders were captured which proved to be Megalepthyphantes sp. a handsome species which seems to be increasing in both range and numbers in the London area. It still awaits description as a recognised species. (see photos).

On the way back to the hut one last sweep of a voluminous ivy patch produced the find of the day: two specimens of the beautiful green crab-spider Diaea dorsata! (see photos) This is the first contemporary record of this spider from central London (that is, within the Circular Road) if not the actual old county of London, and it is interesting to find it in secondary woodland. It has been found in recent years at Hounslow Heath and Cranford Park near Heathrow, in woodland of indeterminate age, but not any further into London. The only previous records are from the 19th century; at Kenwood House and Hampstead Heath. There’s been no sign of it on Hampstead Heath ever since.

Edward Milner

Some remarkable fungi of London.


Comprising over 14,000 hectares of public parks, woodland, gardens and cemeteries, London is the greenest major city in Europe, with 40% of London’s surface area comprising green space that is accessible to the public.  

A wide diversity of habitats, including unimproved grassland, woodland, heathland and scrub with various water features, on various soils from Chalk to  London Clay to Bagshot Sands, provides home to 1000’s of native trees and shrubs such as, oak, beech, birch, willow, poplar, Scots pine and many more.  All of this glorious green space is irresistible to fungi, which thrive across the city landscape. Step into your local green space and you are likely to see fungi of some kind.  Over 600 species have been recorded from Hampstead Heath alone.

Below are a just a small number of the fungi species to be found in London, some of which may be difficult to find elsewhere in Britain.



Podoscypha multizonata - Zoned Rosette

01 Podoscypha multizonata andyoverall

This species has its stronghold in the southern counties of England and London is one of those strongholds. The Zoned Rosette is a red data species and has a Biodiversity Action Plan (BAP) attached to it.  80% of the known world sites are in England, mostly with a southern bias.  It occurs on the roots of broadleaved trees, usually oak, in open woodland or old parks.


 

 

 

 

 

Paxillus obscurosporus - "Fat - Lipped Roll Rim"
02 Paxillus obscurosporus andyoverall


Commonly known as a Roll Rim, this particular species has only recently been described and was new to Britain in 2008. This is a large species, reaching 35cm across, with characteristic, persistent, in-rolled margin.  A common species in London’s parks and open green spaces, often in large numbers beneath lime trees, one of the trees with which it forms a mutual symbiosis.

 

 

 

 

 

 

 

 

 



Grifola frondosa – Hen of the Woods

03 Grifola frondosa andyoverall
Found at the base of deciduous trees, during the autumn, this very well camouflaged, ‘leafy’ polypore was once considered quite rare.  It favours old oak trees in parkland or woodland, so therefore in thrives in the London area as both are in fairly good supply. Although a root rotter, it is a splendid fungus to stumble across whilst out on an autumn stroll.  




 

 

 

 

 

Leccinum duriusculum – Slate Bolete

04 Leccinum duriusculum andyoverall
Mutually symbiotic, forming a mycorrhizal relationship with poplar trees. The Slate Bolete is quite a cosmopolitan species, occurring with different species of poplar, in cemeteries, public parks and with street poplars on grass verges, right across London.  A key identification feature is that the flesh will turn pink and then slate upon cutting in section.



 

 

 

 

 

 

 

Butyriboletus appendiculatus – Oak Bolete

05 Butyriboletus appendiculatusandyoverallMany of the large species of Boletus such as this, are thermophilic, that is to say that they prefer the warm temperatures that a city like London has in being at least 2o C  warmer than areas outside of London. It forms a mutual symbiosis (mycorrhiza) with oak and beech trees. Cold, wet summers will not favour this and other species.


 

 

 

 

 


Amanita phalloides -The Death Cap

06 Amanita phalloidesandyoverall
This deadly mushroom is locally common across London; forming a mutual symbiosis via a mycorrhizal relationship with deciduous trees, favouring oak and hornbeam trees in parks, cemeteries or gardens, from summer to autumn.  White gills, olive to white cap, white stem with greenish hue and white velar remnants, base with sac-like volva. Smell sickly sweet. Onset of poisoning can take up to 36 hours depending on the dose, with severe diarrhoea, vomiting, dehydration, false cessation followed by liver failure, kidney malfunction, coma, death.



 

 

 

 

 

 

Amanita virosa -The Destroying Angel

07 Amanita virosaandyoverall
A much rarer species, with the same outcome as the Death Cap if ingested, occurs in woodland close to London.  Pure and as white as snow, it associates with beech trees in well-established woodlands.  The smooth, conical cap is often off centre, the stem shaggy looking, and the base of the stem, as with the Death Cap, is clothed in white tissue, appearing loose and bag-like.



 

 

 

 

 

 

 

 

 

 

Cortinarius nolaneiformis - "Bellita Webcap" (nolanei = small bell, formis = shaped like)

08 Cortinarius nolaneiformisandyoverall
The genus Cortinarius is believed to contain the greatest number of species among any genera of mushrooms, worldwide. They are commonly known as the webcaps, as they have a web-like veil the covers the gills when young. Gills initially variable in colour but finally rust-brown. This species was recorded during a survey on Hampstead Heath; it turned out to be new to Britain.

 

 

 

 





Russula carpini - "Hornbeam Brittle Gill"

09 Russula carpiniandyoverallThis is a very rare species that associates solely with Carpinus, Hornbeam, as the name suggests.  It is one of the many species of Brittle gills, which characterises the Russula genus, among which species have many different colours in both cap, gills and stem.  

This species was discovered to be new to Middlesex during a survey of Regents Park.



 

 

 

 

 

Laetiporus sulphureus – Chicken of the Woods


10 Laetiporus sulphureusandyoverall
This beautiful bright yellow, salmon fringed polypore, forms large tiers that adorn lots of different trees, in many different habitats right across London.  Usually appearing during late May into the summer months, it is a welcome and colourful sight. It occurs on oak, willow, beech, poplar, cherry, hawthorn, false acacia and more, in parks, gardens, cemeteries and woodlands.


 

 

 

 

Andy Overall.

Common names as per British Mycological Society where available. Otherwise in "quotes".

All photographs ©Andy Overall 2016