Thursday, 21 July 2011

Report on Insects of the Mersey Valley Walk, 03/07/2011

Glorious weather was met with a super turnout, one of the best I can recall for a FoCM event.

The numbers were boosted thanks to the joining of a group of MAD walkers, who tagged on as part of their programme.

Richard and I had chosen a variety of habitats and techniques to try. Indeed, when planning the walk, it was apparent that within not much more than a stone’s throw you could step from meadow, to scrub, to woodland and wetland habitat, all of which have their particular specialist ‘minibeasts’ in residence.

Our first challenge was to survey the ground level dwellers of grassland and scrub, our choice of location the old orchard by Jackson’s Boat Bridge, now well broken into and pedestrianised with footpaths.

A few days earlier we’d secreted around the orchard a few pit traps. These are fairly simple devices, comprising two plastic cups, the kind found on any water cooler, sunk into the ground. The reason for two is so that the inner cup can be removed from the ground smoothly without caving in the hole, which can then be reused for any longer term survey. We poured into each cup a small amount of an alcohol solution so as to quickly drown any fallers-in. Though seeming sound unkind, there is a sound reason for doing this, as in order to get a representative sample it is necessary to quickly stun or kill what happens to fall in. Without this, it is likely that all you’d be left with in the trap would be one fairly fat ground beetle: the top insect predator of the undergrowth, who would have happily fed on any lesser equipped species. Not that it was necessary as the days leading up to the walk were all very sunny, but we placed a piece of plexiglas over the top of the trap, secured into place with tent pegs and tilted at a angle to drain away any rain water from flooding the cup.

We quickly found all 6 traps hidden around the orchard and tipped out their contents into white plastic trays to better observe what we’d caught. All the traps contained some specimens, with most a spattering of small-sized representatives from the arachnids and springtails – two of the more common families which play an important dietary component to larger species. Equally enjoyable during this was the joining of our group of two or three unexpected insect guests, namely a common grasshopper and froghopper, both obligingly seated onto people’s coats, and in the case of the froghopper, onto the rim of the tray, making them easy to be caught in viewing pots.

One of the more impressive specimens, and something we’d hoped to catch, was a species of large ground beetle. The ground beetles are a numerous family, possibly containing many hundreds of species, their individual types only often separated through close observation of such things as the number hairs on their legs. One notable feature of the two we found is that they were all black, including their legs. Other species I’m familiar with, often from turning over logs or old carpet!, exhibit violet or black colourations to their legs or flanks – so, if anyone has any more exact information on the all black species we caught, please let us know.

The next stopping off point was the boggy drainage channel which connects the Mersey to Sale Water Park. This slow moving water is often left undisturbed, the sluice gates connecting it to the Mersey only rarely opened when the water levels get particularly high. As consequence, it’s a rich habitat for many invertebrates. Some of the star groups are the damsel and dragon flies that live out their lifecycles here – and sure enough, we observed in the reeds and grass around the channel a few examples of damsel flies, one of the most attractive a male banded demoiselle, replete with it dark thumb print on its wings.

We then took some scoops out of the channel using pond nets and tipped the contents into our trays. This is always an exciting process as it’s not everyday you come into contact with the invertebrate life of ponds, and when you do I’m always struck by the impressive size and alien shapes that thrive. Species which were observed ranged from leeches, molluscs, including a small fresh waster muscle, pond skaters and water boatmen. However, the best capture was arguably a large, silvery species of diving beetle – seen up close fierce and otherworldly looking.

We rounded off the walk with an exploration of the woodland habitat close to the visitor’s centre at Sale Water Park. Here we all got involved by turning over logs and seeing what we could see living among the dead wood. Slugs were particularly common, with one particularly large example of a leopard slug being particularly impressive. We also found woodlice, lots or millipedes and beetles, all of which play an important role in the breaking down and recycling organic material back into the soil.

Julian Robinson

Tuesday, 19 July 2011


Here’s one for all you fans of the counter-intuitive!

Stonecrops (Sedum sp.) are plants with hairless, succulent, fleshy leaves. These leaves act as water storage organs, hence Stonecrops are adapted for life in dry, sharply-drained environments (sand dunes, rocks, walls etc.). So the odd thing is that three of the Mersey Valley species grow on the river bank, almost at the water’s edge.

The explanation for this, superficially odd, circumstance is that the dry habitats, free from the competition that these small plants would have difficulty coping with, are at the river’s edge.

In some places sandy silt has built up to form miniature sand banks and in others the river banks have been shored up with concrete strips and rafts. These represent almost ideal habitats for Stonecrops, with one small snag, which you may be able to guess – but more of that later.

The three species are as follows:

Biting Stonecrop (Sedum acre) – Top Photo

This yellow flowered species is native to the UK. It is the first of the three species under discussion to flower (May to July). The leaves have a peppery, ‘biting’ taste – hence the name (it’s probably not wise to consume any more than the absolute minimum if you decide to test this out).
Biting Stonecrop is relatively common in the UK – usually on walls, rocks or sand dunes. Nevertheless, it is now rare in the Mersey Valley. The plants in the picture were photographed, just below the Princess Road Bridge, on a sandy layer deposited by the river on a concrete raft.

This species used to grow at the base of the brick walls that line the old sewage works channel that runs parallel to the river bank at the edge of Chorlton Ees. Sadly this population was destroyed a few years ago in a ‘tidying-up’ operation. When I complained I was told that it was, “only a garden escape”. This may or may not be true but garden escapes which become naturalised in the wild (and are not invasive) are intrinsically interesting and should not be carelessly destroyed – particularly not for reasons of tidiness!

I can’t find any old records, for this species, from Chorlton and adjacent areas but, in the mid-19th century, the species was certainly present in the Altrincham/Bowdon area.

White Stonecrop (Sedum album) – Middle Photo

This species is also native to the UK, but is restricted in its distribution as a truly native plant. Nevertheless, it is not infrequently encountered as a naturalised garden escape. It flowers from June to August.

White Stonecrop is now, by far, the commonest Stonecrop on the narrow strips and rafts of concrete at the river’s edge. A couple of weeks ago its massed flowers made a spectacular display at the base of the northern river bank about quarter of a mile west of Crossford Bridge - which carries the A56 over the river near Stretford. I noted some small butterflies feeding on the flowers. There’s one of these butterflies in the photograph. I think that it’s probably a Small Copper (Lycaena phlaeas) – but feel free to disagree with me!

Rock Stonecrop (Sedum forsterianum) – Bottom Photo

Rock Stonecrop is another native plant which also frequently occurs as a garden escape. It’s much less common than White Stonecrop and much more sporadic in its occurrence, but grows in much the same places. It flowers from June to August.
It is generally larger, has much longer slimmer, pointed leaves which are flattened on their upper surfaces.

The snag for these plants is, of course, that periodically they have to endure flooding. You’ve probably seen the Mersey in spate – a rushing, raging torrent which can rise right up to the upper flood banks, completely inundating the Stonecrops’ habitat. It’s amazing that they don’t get washed away – they must have amazingly strong root systems!

What I suspect actually happens that many leaves do break off and are washed downstream. Then, if luck prevails, they will end up on another bit of concrete where they can produce roots and another Stonecrop colony.

Dave Bishop, July 2011

Saturday, 2 July 2011

A Rose by Another Name

Sorry about the title - it's supposed to be a joke. I'm not sure that it works (?) Still. Never mind. Onwards!

In the last article I talked about trying to find the Roses on the list that Leo Grindon published, for the Manchester area, in the mid-19th century. Well, I think that I might have found one of them, and possibly a second - plus one that isn't even on the list.

The one that appears to be more or less definite is the Field Rose (Rosa arvensis). This corresponds to the picture above (although it could be some sort of hybrid, of course). Ironically this plant is on Hardy Farm and I pass it quite regularly (you never know what could be 'hiding in plain sight'!). A couple of key characteristics of this plant are that it has creamy white flowers and the style (the female part in the middle of the flower) is on a short column. An important question is: was it planted in the spot where it grows (as many trees and shrubs were in the 1970/80s) or did arrive of its own accord - perhaps bird seeded? I suppose we'll never know.

Last week I also found, in a hedge in the Albemarle allotments in Withington, a plant with straight prickles - which could be Soft Downy-rose (R. mollis) - but, for various reasons, I'm not sure.

Finally, I've recently found a plant which nearly keys out as Round-leaved Dog-rose (R. obtusifolia). Everything fits (flower colour, sepals, prickles, presence of small, reddish glands on the leaf edges etc.) except that it's supposed to have hairy leaves - and the two specimens that I've found have completely smooth and hairless leaves - baffling!

Dave Bishop, July 2011