23rd January 2018 - Invertebrates of Sussex Rivers: Sam St. Pierre, Vice Chair of the Ouse and Adur Rivers Trust

The Ouse and Adur Rivers Trust started life as The Sussex Ouse Conservation Society. The Society, based in Barcombe Mills, was set up by local residents who were concerned about declining species in their river. Initially they undertook conservation work to improve the health of the Ouse around Barcombe Mills and over time their organisation grew and eventually merged with other organisations leading to a change of name to The Ouse and Adur Rivers Trust. The Ouse and Adur rivers are grouped together because they are designated by DEFRA as having a single catchment area, they have similar characteristics and face similar challenges. The characteristics of the Ouse and Adur rivers can be seen elsewhere in Sussex, for example in the Cuckmere. Currently the Trust has around 160 members who monitor the quality of the water, undertake conservation work and fundraise. Through grants and research funding they now employ one full time project manager and a part time assistant. For a more details visit

Mr St. Pierre limited his presentation to invertebrates that are large enough to be visible to the naked eye and are found in the freshwater areas of these rivers. The vast majority of these invertebrates live on the stream and river beds, with only a few living on the water surface or on water plants. There are a variety of habitats within each river that can be grouped into three main types:

  • Calm water with little flow and a mud river bed. Both the Adur and the Ouse have been modified by man over the centuries and indeed the Ouse had at one time 19 locks. These modifications have resulted in this calm-water type of habitat.
  • Tributaries, which tend to be clear water, fast flowing and often over gravel.
  • Glide, which is water that flows slowly over either silt or gravel and is usually no more than 30-60cm in depth.

The Trust assesses water quality in approximately 50 sites across their two rivers. They use the Biological Monitoring Working Party Protocol which involves using a square, flat bottomed net which is dragged by hand in a zig-zag pattern across the river bed for 3 minutes. All the invertebrates are recorded on a specific form and are graded according to their individual sensitivity to common pollutants. If large numbers of invertebrates that are particularly sensitive to pollutants are found it is extrapolated that the water quality must be good.

Because of the huge number of invertebrates present in these different habitats, Mr St. Pierre chose to highlight a small number that he found particularly interesting. He explained the different types of caddis (sedge) fly larva and explained how the larval cases were made. He presented images of the rare least water snipefly (atrichops crassipes) of which there are only 31 records in the UK. Finally he mentioned the invasive species found in our Sussex rivers. These included the New Zealand Jenkins spireshell snail (potamopyrgus antipodarum), a common but harmless snail that is thought to have been brought over on the steam ships and the signal crayfish (Pacifastacus leniusculus). This North American crayfish can grow up to 30cm and does significant damage to our river banks, local fish and amphibians.

Marion Trew

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6th February 2018 - South Downs National Park – Work of the Rangers

Forty five to fifty of us joined Phillippa Morrison-Price, a Lead Ranger in the South Downs National Park (SDNP) for a wide-ranging talk. She gave us a summary of the purposes and duty of all of the national parks and structured her talk around them.

’Purpose 1: To conserve and enhance the natural beauty, wildlife and cultural heritage of the area.

Purpose 2: To promote opportunities for the understanding and enjoyment of the special qualities of the National Park by the public.

Duty: To seek to foster the social and economic wellbeing of the local communities within the National Park in pursuit of our purposes.’

Key facts about the SDNP – it was originally conceived in the 1940s and eventually became operational in 2011. It is the third largest in England and farming is the largest activity on the Park. It is split into four administrative areas – Western, Wealden Heath, Central and Eastern - and there is a management plan which is being updated.

Purpose 1: To conserve and enhance the natural beauty, wildlife and cultural heritage of the area

There are a range of habitats in the Park, including heath, rivers and streams, chalk grassland (4%) and woodland (24%).

50% of the chalk grassland is in the eastern end and is important because of its diversity of flowering plants and butterflies. Much chalk grassland has been lost to ploughing. The decline of the wool trade and in rabbits following myxomatosis has also had an impact. Restoring chalk grassland through scrub clearance and grazing are therefore major activities for the rangers, working with volunteers, landowners and many other organisations. Ponies (from the Sussex Conservation Pony Trust), cows, sheep, Bagot Goats and rabbits are all used for grazing.

Species specific work is another important activity. Examples include working with farmers to integrate conservation and farming, with a focus on bird habitats; work to encourage the Duke of Burgundy butterfly and the wort-biter cricket; boxes for barn owls; and the reintroduction of water voles on the Meon River in Hampshire (and mink control) where otters have now returned.

As well as wildlife conservation, Phillippa described the work rangers do to preserve the cultural heritage in the park, focusing on archaeological sites, for example, cross dykes and long barrows. There are 616 scheduled monuments in the Park of which 133 are vulnerable or at risk and the rangers have been condition-testing the 133 for Historic England. Other projects include removing scrub at a large Celtic field system (Cloth Farm near Jevington), at an at-risk long barrow (Long Burgh near Alfriston); and at Devil’s Dyke hill fort. Scrub encourages rabbits and other burrowing animals which can undermine ancient monuments.

Other work under Purpose 1 includes advising on landscape character, for example, discouraging unsightly features, like fences on escarpment skylines, or bright green golf course practice nets, and commenting on planning applications.

Purpose 2: To promote opportunities for the understanding and enjoyment of the special qualities of the National Park by the public

Activity under this heading includes learning and outreach work with adults and children, working with people with learning disabilities and others to improve accessibility, work experience for students, events and education, and signage and interpretation. Phillippa mentioned that responsible dog walking was an important part of this work.

There is an extensive network of paths in the Park. Most are the responsibility of the county councils (although Park staff and volunteers are involved in their maintenance) but the paths on access land are the responsibility of the SDNP (4.4% of the National Park is access land). The 100 miles of the South Downs Way has a dedicated SDNP team of two staff.

Sustainable transport is also an important issue supported by leaflets, and a free ViewRanger app available at

Phillippa stressed that the rangers’ work would be impossible without the South Downs Volunteer Ranger Service (around 500 volunteers) and collaboration with local people and organisations throughout the Park.

She also mentioned a number of new projects –

The dewponds project, putting together information on dewponds on the Eastern Downs which will support a bid for funds for renovation. (It costs between £10,000 and £20,000 to renovate each pond.)

The Eastern Downs chalk grassland grazing project which aims to fund a grazing officer

The Truleigh Hill habitats project, using funds from the Rampion Fund to restore chalk grassland and dewponds and create an access trail advised by disabled ramblers; and

The Longlands Wood coppicing project, near Henfield, which is bringing back coppice rotation and promoting small wood management to improve butterfly habitats. It is hoped to reintroduce the Pearl-bordered Fritillary.

The talk ended with a brief summary of the National Park’s duty – ‘to seek to foster the social and economic wellbeing of the local communities within the National Park in pursuit of our purposes’, and was followed by a wide range of questions and comments from members, and a vote of thanks for a very interesting talk from Ruth Young.

Anne Fletcher

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13th February 2018 - Brewer’s Challenge: How many species in your garden?

After Chris Brewer challenged members of the Society to find out how many species of wild animals and plants occurred in their gardens, following the published example of the Leicester University Ecology lecturer, Jennifer Owen, who in 30 years recorded over 2,600 species in her suburban garden, the speaker revealed his current total of just 465…and counting!

Regarding habitats, the back garden has a vegetable and soft fruit area, a lawn with surrounding flower borders and a ‘wild garden’ where grass is allowed full growth away from the fruit trees. At the front, the lawn and borders are supplemented by a small pond and a shaded area dominated by ivy beneath a laburnum tree. Both front and back gardens include small beech hedges.

Prior to Chris’s challenge in 2014, birds (currently 39) had been recorded since 1992, the five rarest being turtle dove, bullfinch, firecrest, spotted flycatcher and rose-ringed parakeet with no more than two sightings. An unusual visitor was the red-legged partridge that spent 6 hours rooting around grasses and agapantha plants. The picture of a male blackcap showed a bird dazed by hitting the front windows, but the good news is that it flew away after about 15 minutes.

More colourful creatures were illustrated under the heading of Lepidoptera – butterflies (18) and moths (131). The most recent butterflies were small copper, holly blue, large skipper, small heath and a fly-over clouded yellow. As far as moths are concerned, leaving the light on in the bathroom, initially by accident, and the window open, turned out to be the main reason for a haul of 75 moths and 56 micro-moths on the property! A good start was the Fern Smut (Psychoides filicivora), found near ferns at the base of the north-east-facing fence, of which fewer than a dozen sightings had previously been recorded by the Sussex Moth Group. Bob Foreman of the Sussex Biodiversity Record Centre kindly verified the sighting. A few moth larvae were also illustrated: the spectacular Vapourer, and the equally striking Lackey, which eventually turns into a rather drab brown adult. Amongst adult moths shown were the Large Long-Horn Micro-moth, with antennae more than twice as long as its body and with a name to match, Nematopogon swammerdamella, and a fuzzy hummingbird hawk-moth in perpetual motion. A cabbage moth caterpillar, “ruining cabbages by burrowing into the heart”, had been liberated from the head of one of the speaker’s treasured Brussel Sprout plants!

8 mammals (badger, bat sp., brown rat, fox, grey squirrel, rabbit, hedgehog, mouse sp.) have been recorded, of which the fox is most often seen and heard.

At a smaller scale, the Hymenoptera (ants(1), wasps(13) and bees(8)) provide some spectacular images in close up, such as the German Wasp on a tennis ball that illustrated how facial pattern is used for ID. During 2016 two wasp nests were found in the garden, one in a hole in the wild garden, the other beneath a green waste heap. The sources of nest material appeared to be a pile of thin logs and a wooden fence. Both nests were broken into, probably by a badger, activity that has been previously reported. In the front garden Common Carder Bees occupied the base of an ornamental grass. A digger wasp, Gorytes laticinctus was shown with its prey, possibly a froghopper. A variety of colourful bees, Andrena haemorrhoa, Andrena fulva, Bombus pratorum, Bombus rupestris and Bombus terrestris were illustrated, on a variety of flowers.

There followed a sample of the 49 recorded Diptera, including a range of strikingly patterned hoverflies, the two species of Rhingia hoverflies that are distinguished by their long snouts, and the curious Eristalis nemorum pairing in which the male customarily hovers a few centimetres above the female. One way to differentiate Eristalis species is to record their distinctive facial differences.

The front garden includes a small pond reserved for purely wild creatures, no fish having been added to it. Common backswimmer, smooth newt, and several of the nine recorded dragonflies were illustrated, including azure damselfly, southern hawker, common darter, and broad-bodied chaser.

The front lawn, especially, is mown sparingly to allow grasses, such as Yorkshire Fog, and wild flowers (birdsfoot trefoil, red and white clover, hawksbeard sp. etc.) to mature, to the benefit of Hymenoptera. Evidence that the front lawn may derive from the original local chalk grassland is provided by the annual presence of several autumn ladies tresses and the recent appearance of parrot, golden and blackening waxcaps, fungi probably indicative of a lack of fertilisers and other chemicals. Nothing has been added to the lawn over the last 25 years.

A single lichen was illustrated to represent this complex group of life forms that have yet to be given serious identification time. The slide showing a group of woodlice feasting on an unidentified tasty morsel reminded the speaker that it was also the meeting teatime and a break was called.

With tea over, some less familiar evidence of different insects was introduced – leaf mines, the complex, often distinctive patterns left behind on leaves after larvae have chomped their way through the inside of leaves, sometimes leaving behind trails of frass. The impact of the horse chestnut leaf mining moth, liberated from the surface of a garden water butt, presumably associated with the large horse chestnut tree in a neighbours garden was illustrated by an image from the RHS. The holly leaf miner fly leaves an irregular yellowish and reddish patch on holly leaves from which blue tits are reported to have been seen to be taking larvae. A selection of seasonal patterns was illustrated from a useful book – Micro-Moth Field Tips by Ben Smart.

And then we came to the arachnaphobe’s nightmare, spiders. The handsome garden spider, hanging from the greenhouse ceiling was strikingly patterned, alongside a variety of different species. Nuctea umbratica was shown apparently wrapping up its slug prey, and a wasp and fly seemed both to have succumbed to spiders lying in wait beneath flower heads.

A mating pair of frogs, representing the 5 reptile and amphibian species, was shown partially camouflaged amongst dead leaves and plant debris. A group of different slugs, were identified for the speaker by Chris de Feu who believed they had assembled around a source of food. A cluster of small white eggs were probably from the garden snail, Cornu aspersa, although on the day after first seen an Arion slug was observed next to the pile. Finally, beetles (20) were represented by the common, black Nebria brevicollis, the large, bright green rose chafer, the very hairy summer chafer and the spectacular swollen-thighed beetle, and bugs (25) by the ant damsel bug, the attractive red and black Corizus hyascyami and the dock bug. After questions Chris Brewer gave a generous vote of thanks.

This talk replaced the advertised one on Wealden Heath’s Breeding Birds by Alan Perry who had suffered a broken fibula. It is hoped that he can present during the next winter programme.

Colin Whiteman

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page updated 22nd February 2018