FRESHWATER INVERTEBRATE RECORDER’S ANNUAL REPORT 2010

25 AQUATIC INVERTEBRATE REPORT

Trans. Suffolk Nat. Soc. 46 (2010)

FRESHWATER INVERTEBRATE RECORDER’S ANNUAL REPORT 2010

ADRIAN CHALKLEY

This report covers the period from May 2009 to May 2010 and will follow the format used in previous years by dividing the freshwater invertebrate community into the major groups. Within the report wherever a common name exists for a species it is given before the Latin and the national status, if known, is given in brackets afterwards. In addition to reporting the more interesting or significant records made during this year I offer two aids aimed at increasing the number of records I receive for the county database. Both of these aids can be downloaded from my website at http://www.boxvalley.co.uk where links to both can be found on the home page.

Help for non-specialists I mentioned in my last report that I put have a leaflet for non specialists on my website which will allow identification to species level of a number of invertebrates that can be found in ponds and streams. All of these are easily identified and for each we need more records. During the year I have given copies of this leaflet to small groups that I have talked to and several records have indeed come in. I hope more SNS members will try it out and send in some records during this coming year.

Software for specialists Also on my website is a piece of software called SAFIS, Site Analysis for Freshwater Invertebrate Surveys. This, as the name implies, provides an instant analysis of the water quality and the biodiversity value of a freshwater site. However it does need the user to type in a full list of the scientific names of species recorded during a survey and as such is useful only to specialists and professionals. A full description of the software including screenshots can be found on the website.

The Ephemeroptera (Mayflies) The two most commonly recorded mayfly larvae continue to be the Large Dark Olive, Baetis rhodani in flowing water and the Pond Olive, Cloeon dipterum in still waters. Both these species have been recorded wherever I have been across the county this year. Slightly less frequent but still wide spread has been the White Midge, Caenis luctuosa recorded from several locations including Glevering Bridge on the River Deben, Shelley Bridge on the Brett and the Little Ouse at Blo’ Norton. The Small Spurwing, Centroptilum luteolum has proved more elusive this year than last but was recorded again on the River Box and River Brett along with the Blue Winged Olive, Serratella ignita. The Turkey Brown, Paraleptophlebia submarginata, was common in the River Brett in April.

In September I visited a favourite part of the River Box, a riffle area covered in fine stones in Boxford. Here I recorded particularly large numbers of the nymphs of the burrowing mayfly Ephemera danica. The fisherman’s name for this large insect is the Green Drake and it occurs there together with the related species the Drake Mackerel, Ephemera vulgata which is also common in many side streams of both the Box and the Brett. The Ephemera


Suffolk Natural History, Vol. 46 26

are unique amongst the British Ephemeroptera in having a semivoltine life cycle. That is they have one generation every two or even three years and because of this long period of growth the larvae may be found in suitable gravel or silt stream beds at all times of the year. However research (Tokeshi, 1985) has found that the larval growth period is very temperature dependant, hence if climate change increases the number of degree days experienced by larvae in Suffolk we could see a shortening of the life cycle and perhaps a lengthening of the adult flight period. This flight period is at present from May to August. Walking in waterside meadows during this period often affords the general naturalist the opportunity to see the adults flying in large swarms during their elaborate mating displays. The swarms are composed of males which fly up and down to attract the females, usually over some convenient marker such as a taller bush serving to orientate the swarm. Into this dancing swarm the females will fly and mate with a male as they descend to the ground. The female will later release the eggs in batches onto the surface of the stream.

The population of Paraleptophlebia werneri (RDB 3) in a small stream at Elmsett is still the only one discovered in Suffolk and the only one known in Eastern Britain. This certainly makes it Suffolk’s rarest mayfly and so every year since they were discovered in 2006 I check the site during the short season when the nymphs are large enough to be easily identified without undue disturbance. They are very delicate and easily damaged in a net; they also die very quickly if the water warms too fast. Therefore examination is best done by scooping larvae out of the stream in a small white plastic spoon. The identification is easily confirmed with a hand lens and the nymphs are returned within a few moments never having left the water which has no time to warm. After the harsh winter I was interested to see how they were faring. In the part of the stream with the best habitat they were present in very large numbers, with an estimated 400 per square metre. However the length of stream in which they were present has reduced from about 5 km in 2008 to only 1·5 km in 2010. They seem to have disappeared from the wider section downstream which they shared with the related species Habrophlebia fusca, which also could not be located this year. Being small and insignificant neither species has a common or fisherman’s name.

The Coleoptera (Water Beetles) As always I have had a good number of Coleoptera & Heteroptera records from Dr Stuart Warrington of the National Trust for which I extend my thanks. This included many with the status of Local or better. There are too many individual records to list here, however there are some which are new to my database and these are:

a lesser diving beetle, Hydroglyphus pusillus (Notable B) which was taken at Ickworth. At Orford, Stuart found the water scavenger beetle, Enochrus halophilus, (Notable A), together with the crawling water beetle, Peltodytes caesus (Notable B) and another water scavenger beetle, Enochrus ochropterus (Notable B).



In August I ran a public pond dipping day at Foxburrow Farm hosted by the Suffolk Wildlife Trust. This was well attended and produced records for the SWT reserve including the almost ubiquitous Furrowed Water Beetle, Acilius sulcatus. Also found was the small, red, lesser diving beetle, Hyphydrus ovatus and a slightly greenish water scavenger beetle, Hydrobius fuscipes. Each of these three is easy to identify and common so hopefully some of the course participants will recognise them again and send in records.

In the same month Juliet Hawkins reported a further record of the Silver Water Beetle, Hydrophilus piceus (RDB 3) at a new pond in Helmingham parish which has not, to our knowledge, been surveyed before. This is our largest water beetle and also very easy to recognise (Plate 9), though the number of records for this species is relatively small. In the last few years we have seen a number taken near to the Suffolk coast and a new record further towards central Suffolk is most interesting.

In September I ran an identification course at Flatford Mill during which students found the oddly named Artist Whirligig, Gyrinus urinator (Notable B) in the River Box at Polstead. This is a species which seems to have been turning up quite frequently in recent years and is certainly worth looking for.

In the same month the London Freshwater Group met at Blo’ Norton Fen. Full details of the survey can be downloaded from the LFG website at http://londonfreshwatergroup.co.uk

Whilst at the Fen Robert Aquilina found the Water Scavenger beetle, Cercyon sternalis (Local ) for which I have only eleven other records, including a site at Little Fen nearby. In the Scrape at Parkers Piece the Lesser Diving Beetle, Hydroglyphus geminus (Notable B) was fairly common and was found by both Steve Kett and Robert Aquilina. Several other Local species were also found including the lesser diving beetle, Hygrotus impressopunctatus; the water scavenger, Laccophilus minutus; the crawling beetle Haliplus obliquus and the Caspian Whirligig, Gyrinus caspius.

The last catch of the day went to Dr Carl Sayer, one of the botanists, at the garden pond of Joanne Pitt who had invited us to the Little Ouse Headwaters Project and lives nearby. Carl eventually triumphed after chasing a large beetle round the pond for some time, this was identified as a female Dytiscus marginalis (Plate 10). Although this is the most common species of Great Diving Beetle, it was fittingly large to provide a good end to the day. D. marginalis may be found almost anywhere at any time which is shown by the fact that it also appeared in our catch in the R. Brett at Shelley during my November course for the Field Studies Council, despite cold weather and rising river levels.

In my report in 2007 I described a large swarm of Whirligig beetles which I observed at Lound reservoir. (Chalkley, 2007: 60). On 23 September 2009 at Glevering Bridge on the River Deben I witnessed a similar swarm. These swarms are often referred to as ‘Schools’ or ‘Flotillas’ of whirligigs and a general description of this one has already appeared in White Admiral (Chalkley, 2009a: 3). These autumn gatherings are infrequent, requiring one to be in the right place at the right time.

My 2007 observation concerned a school composed in the main of the Mariner Whirligig, Gyrinus marinus (common) with very occasional



specimens of the Common Whirligig, G substriatus, whereas the River Deben school comprised three species, the Bronze Whirligig, G. Aeratus (Notable B) and the Artist Whirligig, G urinator (Notable B), again together with G substriatus.

Estimated numbers in the school seen at Lound in 2007 were 2,500 plus and numbers in the Deben must have been similar. It is interesting to note that the Deben school had a ratio of 24:1 for G aeratus : G substriatus, which was broadly similar to Lound where again G. substriatus was the more infrequent species. However the ratio for G aeratus : G urinator was much larger at 5:1. Drawing any conclusions from such few observations is obviously inappropriate but does allow for more critical observation at the next opportunity, whenever it may occur. I should be very interested to hear of any similar observations of whirligig ‘schools’ with the approximate date and location.

To conclude this section are a couple of early season records from 2010. In April Juliet Hawkins’ farm pond provided the crawling water beetle, Haliplus laminatus (Notable B). This is only the third site on my database for this species, the other two being found in 1994. However Claude Morley did find it in Ipswich in 1895 and there is a slightly later record by the Rev. E. J. Pearce from 1931 at Barton Mills on the River Lark. I must also thank Juliet, not only for sending in beetle records but also for allowing students on my courses to use her farm ponds over the last few years.

In May whilst surveying for Great Crested Newt eggs I found the Diving Beetle, Agabus melanarius (Notable B) in a pond at Polstead. This is a species for which I have no other records in Suffolk and which only appears on the National Biodiversity Network from Norfolk and Essex.

The Heteroptera (Water Bugs) The early part of the year produced no surprising records although it is worth noting that in July at the annual survey of the Center Parcs site at Elveden Sigara iactans was again recorded. More details of this Lesser Water Boatman which has spread from the continent were included in last year’s Transactions (Chalkley, 2009b: 19). Elveden remains only the second Suffolk site for this species and numbers do not seem to have increased in the intervening year.

At the pond dipping day at Foxburrow Farm in August some very keen participants provided useful bug records including the Toothed Pondskater, Gerris odontogaster (Common) and the Saucer Bug, Ilyocoris cimicoides (Common). Giving out trial copies of the leaflet mentioned at the start of this article produced several records later in the year including the following bugs. Gillian Coles found the Water Scorpion, Nepa cinerea at Foxburrow, which had not been seen there before. Later that month Mrs Jean Ashburn found the Water Measurer, Hydrometra stagnorum in her artificial garden pond in Wickham Market. My thanks to these two ladies for sending in their first freshwater records. We have so few records from garden ponds that we have no real appreciation of their importance to invertebrate communities. Yet the number of garden ponds is very large and I would welcome records of even the most common species in these habitats, which can be identified from the leaflet mentioned.



One water bug that fascinated people at Foxburrow was the Lesser Water Cricket, Microvelia reticulata (Local) which was common on the water surface of the two main ponds. This fascination was repeated for me whilst surveying in the Norfolk Broads during the summer when I found a number of the much rarer Microvelia beunoi (RDB3) which has unfortunately not been recorded in Suffolk.

During the September meeting at Blo’ Norton of the London Freshwater Group, the Sphagnum Bug, Hebrus ruficeps (Local) was recorded. In Suffolk it has only been recorded once with certainty (I have examined the specimens in Ipswich Museum.) This was in 1942 when it was found by Claude Morley at Thelnetham Fen, only a stones throw from the Blo’ Norton record 67 years later! An excellent record therefore although I believe this particular stones throw takes us just into Norfolk! There are also a couple of newer records on the National Biodiversity Network from the Suffolk coastal area in the 1980’s which need to be checked out. Other finds on the day were a Water Boatman, Notonecta viridis (Local) & Plea minutissima (Local) both found in Jo’s garden pond by Robert Aquilina, whilst I took a different Boatman, Notonecta maculata (Local) and a Corixid bug, Hesperocorixa moesta (Notable b) from the same small artificial pool.

Late season records were the Pondskater, Gerris lateralis (local) from Ray Ruffell’s garden pond in September. In October common Corixids such as Sigara dorsalis (Very Common) and Sigara distincta (Occasional) were still numerous in the River Brett at Shelley Bridge, amongst the emergent vegetation which would soon vanish in the cold of winter. Of course winter cold is less of a problem to aquatic invertebrates than terrestrial, after all water rarely freezes completely and temperatures are usually maintained just above zero. The water cricket, Velia caprai is common on many of our Suffolk streams and rivers and there is a large colony on my garden stream. In most winters they are active throughout the coldest months and will be seen scuttling around on the surface film by day or night. However in this last winter, the coldest for some years, they vanished during the heavy snow and subsequent stream surge on the 19 January. Vacating the water during periods of spate is by no means unusual for this insect; they are quite at home amongst vegetation on the bank although exactly what triggers their mass movement out of harms way is unknown. Apparently they hibernated for two months out of the water this winter for they could not then be found until one night in late March when a torchlight observation revealed they had returned en masse. The previous night none could be found!

The Hirudinea (Leeches) Very few leech records ever get sent in for the database and I have done little work on them myself this year. However several species continue to appear regularly; the Fish Leech, Piscicola geometra in the Rivers Deben, Brett and Box, Erpobdella octoculata at Carlton Marshes, Thelnetham, Milden and the River Brett, Erpobdella testacea in Flowton Brook, the Brett and the Box, Glossiphonia complanata at Thelnetham and the Deben, Helobdella stagnalis at Milden and Thelnetham, Theromyzon tessulatum at Carlton, Milden and Elveden.



The Horse Leech, Haemopsis sanguisuga continues to be a rarer sighting than most of the species for reasons outlined previously (Chalkley, 2009b: 19). Spring is the mating time for these creatures and this year Horse Leeches reappeared in my garden stream on 6 May 2010, two weeks earlier than 2009 where the date was 20 May Numbers reached a maximum of 11 swimming together in a large group at midnight on the 24 May 2009. A cold snap this year seems to have slowed things down and at the time of writing no large groups have yet been seen.

The Trichoptera (Caddis Flies) Some interesting caddis have been found during the year, mostly identified from larvae for which modern keys are available. Unfortunately the available keys to adults are rather old now and are not easy to use.

In July David Nash recorded the Longhorn caddis, Oecetis furva (Local) at his light trap in Brantham, this was only the 2nd modern county record, the other being a single larva from Elveden in 2005. Interestingly the Morley collection in Ipswich museum has no specimens at all of this species. It is found in the emergent vegetation of large ponds and lakes, although David knows of no suitable pond nearby. By the time August arrived David was still getting O. furva to his new light trap, some nights up to 1000 would arrive!

Students on my FSC courses usually visit the same sites to collect samples so we can compare results with previous courses, many species turn up on every visit but even after several years there are usually some new records. In September we found the Great Red Sedge, Phryganea grandis (Local) from Juliet Hawkins’ ponds at Milden. There are relatively few modern records for P. grandis and mostly they are from the 80’s and 90’s but it was found at Cherry Hill in 2002 and was also taken once before at Milden in 2003. The Morley collection of adults has nine Suffolk specimens from the turn of the 20th Century collected from the Gipping, Herringfleet, Brandon, Fritton and Monk Soham.

At Glevering Bridge in September, after watching the whirligig ‘School’ I found the following caddis larvae; the Medium Sedge, Goera pilosa, the Grouse Wing Mystacides longicornis and, with no common names, Molanna angustata, Limnephilus lunatus (Plate 11) and Limnephilus rhombicus all of which are common.

Sampling at Shelley Bridge on the River Brett during my October FSC course produced the following caseless caddis larvae; the Grey Flag, Hydropsyche pellucidula together with the Marbelled Sedge, H. angustipennis and the Dark Spotted Sedge, Polycentropus flavomaculatus. Again all are listed as common. These caddis larvae do not make cases to live inside; instead the Hydropsychid species spin an underwater arched net from a secretion rather like spider silk. This is used to trap food particles floating downstream and the larvae may patrol the net or rest within an adjacent tubular silken retreat. Polycentropodid larvae construct a silken tube in which they live and which has a funnel shaped net at either end which serves to ensnare live prey.



Despite the increasingly cold weather in December I found an actively crawling Micropterna sequax larva in my home stream. This species is listed as very common but we have only three sites recorded for it in Suffolk. I have found it in my own stream at various dates from 1990, at Tiger Hill near Bures in 1992 and from the River Tang in 1994. Morley took three adults at light in Monks Soham in 1906, 1933 and 1935 and one at Lowestoft in 1908. Ian Wallace, the national recording scheme coordinator, says the preferred habitat is streams which usually diminish in summer on a mineral bed. This is certainly true of the sites mentioned, but there are many other similar habitats I have surveyed in which no larvae have been found.

My April FSC course produced only the second county record on my database of the Mottled Sedge, Glyphotaelius pellucidus (common). There are several Suffolk adult specimens in the Morley collection at Ipswich Museum from the early 1900’s. However the Morley specimens are also from only a few locations, Monk Soham, Fritton, Tuddenham Fen, & Foxhall. So although listed as common it was perhaps never as easy to find in Suffolk as some other species. This specimen, caught and identified by Rachel Jackson on my course, was in a large pond at Milden which seems a typical good Suffolk pond and a good general caddis habitat.

During the last two years I have spent some time cataloguing the Morley caddis collection at the Ipswich Museum, some details of which have been mentioned above. Dating from the late 1890’s and early 1900’s the collection provides records and specimens of the adults of 68 species which he found in Suffolk, sometimes by netting but often he took them at light and occasionally he attracted them by sugaring. Our modern records are of 78 species, mostly as larval records although some are adults. Of the Morley adults only 16 species have no corresponding modern records. Of the modern records 26 are not represented as adults in the museum. Adding both modern and Morley’s records brings the county species list up to 94 out of approximately 200 species on the British list. The most important of Morley’s records is doubtless Ironoquia dubia (RDB 2) which he caught at his house at Monk Soham in 1906. The specimen is now in the Museum of Scotland and not in Ipswich and it has not been found again, despite further searches in the vicinity of the original site. Although Morley took his single specimen at light Ian Wallace of Liverpool University informs me that it is unlikely to have flown far from the stream it pupated in and it may be that the local habitat has changed so much that the original population in Monk Soham is no more.

Another species in the Ipswich collection, listed as common but which has not been found recently as larvae is Crunoecia irrorata. This is a species which occurs in permanent trickles at the margins of tiny woodland streams and Morley had only a single specimen. I suspect it still occurs though few light trapped caddis are identified these days and few studies are done on this particular habitat. A similar situation may well occur with Trichostegia minor, another common caddis with unusual larval preferences which are for stagnant leaf filled pools which form in winter in woods and fens. Morley took five adults of this species at a single location bearing the cryptic label entry ‘L Rd Stn’ on the 19 June 1906.



The Mollusca (Water Snails) In a previous article (Chalkley, 2007: 61) I discussed an American freshwater limpet, Ferrissia clessiniana (note the name change, it used to be F. wautieri) which is spreading in British freshwaters. This had been found at Center Parcs, Elveden in 2006 in small numbers along with the native Lake Limpet, Acroloxus lacustris. In my 2007 survey the American limpet seemed more common than the native. Last year the July 2009 survey revealed that the ratio of Ferrisia to Ancylus was now 3:1 and it seems that it is out breeding the native limpet. I look forward to this year’s survey to see if this trend continues. My thanks to the Center Parcs company for commissioning these annual surveys which are an ideal way to spot faunal changes over time.

Students on my courses visit the river Brett to sample the invertebrate fauna and here the striking mollusc Theodoxus fluviatilis (Plate 12) can always be found at any time of the year. Commonly called the Nerite this snail is frequently found in Suffolk rivers and is one of the easiest to find by simply picking up and examining stones to which it attaches itself to graze on algae. It is also one of the easiest to identify with a unique shape and colour, although the colour is only noticeable if the shell is clean. More records from any general naturalist would be very welcome, all it takes is to pick up a few stones and check on the downloadable identification sheet.

Miscellaneous Orders Later in September I visited a favourite part of the River Box, a riffle area covered in fine stones in Boxford. This is a reliable site for finding the freshwater sponge Ephydatia fluviatilis, which was present in abundance encrusting the roots of riverside trees such as Willow and Alder.

One member on my April course, Angus Menzies, was keen on identifying Blackflies and found Simulium lundstrom in the River Box at Polstead. The Simuliidae are a neglected group and so this is a new record for the Suffolk database, making a total of ten species in the Suffolk list out of a British list of around 30.

My final two miscellaneous species are not invertebrates at all. Firstly in the icy weather in early January I was surprised to be able from my armchair to watch a kingfisher hunting small fish, Stickleback and Rudd, in the stream in my garden! The depth of water being only 15 to 20 centimetres it did not seem to find hunting as easy as it normally does a hundred metres upstream in the lake from which the stream is fed. But it was obviously driven into my garden as the lake was completely iced over whereas my stream, being moving water, never freezes.

The second species is the Eel, Anguilla anguilla. For many years it was a common sight to see eels travelling up my stream towards the lake, or in the rain slithering across the grass in the same direction. One took up residence in the end of a drainage pipe that opens under water by some steps down to the stream. I used to watch it when observing the stream by torchlight at night and as it grew larger over time I would marvel at the way it could swim into the pipe head first and a few moments later out would pop its head waiting for prey to pass by. Eventually it seemed only a little smaller than the drain pipe



but still managed to bend double and turn around inside. Unfortunately the time came for it to disappear; hopefully it migrated successfully to breed in the Sargasso. The decline in eel populations is well documented and for the last few years we have not been graced by any eels and the garden stream seems much emptier without them. But to end on a positive note, just as I was finishing typing this article in May I went down to check again by torchlight and there, in the end of the same drainpipe, was the head of another, smaller eel. As I watched it darted out and wriggled into the mud, pursuing some small creature which I was unable to see, and then it swam back into its hole. Hopefully this is the start of a couple of year’s residence, and what a privilege it will be to watch!

References Tokeshi, M. (1985). Life-cycle and production of the burrowing mayfly,

Ephemera danica:a new method for establishing degree-days for growth. Journal of Animal Ecology 54: 919–930

Chalkley, A. K. (2007). Freshwater Invertebrate Recorder’s Annual Report 2007. Trans. Suffolk Nat. Soc. 43: 59–62.

Chalkley, A. K. (2009a). An early autumn day on the Deben. White Admiral 74: 3–5.

Chalkley, A. K. (2009b). Freshwater Invertebrate Recorder’s Annual Report 2009. Trans. Suffolk Nat. Soc. 45: 17–20.

Adrian Chalkley, Freshwater Invertebrate Recorder 37 Brook Hall Road Boxford Suffolk CO10 5HS Email: [email protected] Phone 01787210140

Plate 10: Great Diving Beetle, Dytiscus marginalis L. another large, and common aquatic beetle (p. 27).

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Plate 9: Silver Water Beetle, Hydrophilus piceus L. our largest aquatic beetle. Found in a pond at Helmingham (p. 27).

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Plate 11: Caddis Fly, Limnephilus lunatus Curtis. Caddis flies belong to the order Trichoptera - which means hairy wings (p. 30).

Plate 12: A freshwater snail, the Nerite, Theodoxus fluviatilis (L.) frequent in the R. Brett (p. 32).

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Documents

FRESHWATER INVERTEBRATE RECORDER’S ANNUAL REPORT 2010