Freshwater Invertebrate Recorder’s Annual Report 2009

RUNNING HEAD

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Freshwater Invertebrate Recorder’s Annual Report 2009 ADRIAN CHALKLEY As no report appeared in Transactions 44, I will cover below the period from July 2007 to May 2009. I am grateful to have received a number of records from Stephen Youell who has been working in the north-east of the county; at Camps Heath, Oulton Marshes and Carlton Marshes. I have also received records from Emily Dresner, an MSc student from UCL who chose Suffolk farm ponds as the subject for her dissertation. Unfortunately naturalists like Stephen and Emily, working in freshwater habitats, remain very thin on the ground. In an effort to encourage others to contribute records of even common species, I have produced a leaflet on easily identified freshwater invertebrates which can be freely downloaded from the society website at www.sns.org.uk.

Many people will find that in their garden ponds or in their local streams there are invertebrates they can identify from the leaflet and I would welcome their records. I hope therefore, that in my 2010 report I can provide a longer list of records from SNS members. Meanwhile, below are some of the more interesting records from the last year and a half.

Ephemeroptera (Mayflies) In my previous reports I have mentioned the rare species Paraleptophlebia werneri occurring near Elmsett. During the short larval seasons in 2008 and 2009, nearby streams with similar habitats were surveyed, although only the similar species Habrophlebia fusca, from the same family Leptophlebiidae, was found. However, during both seasons the population of P. werneri continued to be stable and still coexists along about 5 km of the original stream with H. fusca.

Mayflies are one of the few freshwater invertebrates to have rather exotic common names. Generally in Suffolk it is the Pond Olive, Cloeon dipterum which is most likely to be found in still water and the Large Dark Olive, Baetis rhodani in rivers or streams. However, several other species do occur in slightly smaller numbers and I note that numbers of the Blue Winged Olive, Serratella ignita and the Small Spurwing, Centroptilum luteolum both seem to be on the increase after a few years of reduced records. Also, the two large burrowing species; the Mayfly, Ephemera vulgata and the Green Drake, E. danica are frequently to be found in extremely large numbers in our lowland rivers. I have recently been doing some quadrat based drift net surveys in tributaries of the Stour and the Lark where densities of larvae are often over 150 per square metre in suitable substrates. These two species are usually the ones you may have noticed forming large clouds of ‘dancing’ males in the late afternoon sun over riverside bushes.

Coleoptera (Water Beetles) There are over 500 species of water beetles occurring in the British Isles and many are recorded very frequently in Suffolk; the red, rotund Hyphydrus ovatus surely being a candidate for the most common. Another beetle which has been found with increasing regularity, and one which is easily recognisable, is the Screech Beetle, Hygrobia hermanni. The mating of this

Trans. Suffolk Nat. Soc. 45 (2009)

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species was described in White Admiral 67 by Christine McClure and I again recorded it mating during the same sort of time period of early May in 2009 at Carlton Marshes. Despite its common status, more records of this species are needed in order to begin to see a clear distribution pattern for the county. Due to the sound it makes when caught it is easy to identify, although I would describe it as making a buzz rather than a screech! Amongst the species seen less frequently was the notable diving beetle Agabus chalconatus found in a pond near Rushbrooke in May 2008. As part of her MSc dissertation Emily Dresner from UCL took the notable species Berosus affinis, a water scavenger beetle showing a preference for low shade, from a recently restored farm pond near Framsden. She also found another water scavenger, Helochares lividus and the diving beetle Rhantus frontalis both of which are of notable status.

Two species of local status taken in the River Box in September 2007 were the Hairy Whirligig, Orectochilus villosus and Hydroporus incognitus, a species of lesser diving beetle. Finally, the Great Silver Water Beetle, Hydrophilus piceus was found in April 2007 by Stephen Youell at Camps Heath Nature Reserve. This is a useful addition to the recent records for this RDB3 species from Orford Ness by Stuart Warrington and Jim Askins.

Heteroptera (Water Bugs) Amongst records sent in by Stephen Youell from Oulton Marshes were Gerris lateralis, a pond skater very infrequently recorded in the county. Although nationally of local status this is surely a notable species for Suffolk. Similarly of notable status for the county is the Little Pond Skater Gerris argentatus, recorded by myself at Carlton Marshes in April 2009. Only two modern records exist for this species, which is rarely recorded in the county. The other record is in the same general area from Lound in 2006. Stephen also found the nationally scarce water cricket Microvelia pygmaea at Oulton Marshes. This tiny surface bug, less than 2 mm long, is widespread but very infrequently recorded in Suffolk, although the similar species M. reticulata is quite common if you know where to look. I found the third species of micro cricket M. buenoi, during survey work in the Broads in May 2009. M. buenoi is of RDB3 status but probably does not survive in Suffolk.

Also in the family Veliidae, there are two much larger Water Crickets of which Velia caprai is a very common surface bug in streams across the county and V. saulii only occurs across the border in Norfolk as far as we know. In early summer 2007, I found that two common whirligig beetles, Gyrinus substriatus had joined the large colony of V. caprai in the pond by the stream in my garden. The response of the crickets was fascinating, they literally ‘ganged up’ on the whirligigs taking it in turns to dart in and harass them until, worn out by constant attack, the incomers were obliged to fly elsewhere. The water measurer Hydrometra stagnorum, another surface bug, shares the pond with Velia and yet Hydrometra is well tolerated by Velia. Perhaps this is because both Velia and Gyrinus have similar fast moving, random hunting movements and Hydrometra is a slow moving opportunistic feeder unlikely to compete with the water crickets. A fuller description of this behaviour may be found in Het News 11; Spring 2008 downloadable at www.hetnews.org.uk.

Trans. Suffolk Nat. Soc. 45 (2009)

RUNNING HEAD FRESHWATER INVERTEBRATES

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In White Admiral 69, I reported the first British record of the recently arrived continental species of Lesser Water Boatman, Sigara iactans. This was discovered whilst re-examining samples collected from Framlingham Mere in 2001. Last year, I found more specimens in two lakes at Center Parcs in Elveden. I am sure this species will turn up again but, with 7 years between records, it appears that although S. iactans is spreading widely, it is not occurring in as large numbers as was first thought.

Hirudinea (Leeches) Leeches are less often recorded than many other freshwater invertebrates, possibly because they are not easily preserved and therefore need to be identified on site, and possibly because they have something of a poor public image! It was therefore pleasing to see several new records from Stephen Youell from the north of the county where I get to only infrequently. Amongst these records are Erpobdella testacea and E. octoculata, both general predators of aquatic invertebrates. The first species alone was recorded from Camps Heath but both were found at Oulton Marshes and Carlton Marshes.

The last two sites also provided the slightly less common Hemiclepsis marginata which is sanguivorous on amphibians and fish. From Oulton and Carlton also came records of Helobdella stagnalis, an easily recognisable small invertebrate predator which is one of the commonest leeches in the county. All three reserves, not surprisingly, had the Duck Leech, Theromyzon tessulatum. A parasite of water fowl, this leech evolved to use air travel for dispersal many years before man managed to and consequently is very common throughout the northern hemisphere.

Finally, Stephen also provided a record in May 2008 of the Horse Leech, Haemopsis sanguisuga from Butcher’s Marsh on the Oulton Marshes Reserve. ‘Horse’ merely refers to the large size of this leech which I am sure is under recorded in the county. Spending a lot of the year out of water in wet soil, this species is not always easy to find. Each year during mid to late May and early June I see H. sanguisuga in large numbers in the stream in my garden as they begin to mate. However, it is July or August before one can find their cocoons under stones on the bank. Thereafter only the occasional adult may be seen, usually at night by torchlight, in the water.

Trichoptera (Caddis Flies) As time allowed during the last 18 months I have been cataloguing the collection of Trichoptera specimens by Claude Morley at the Ipswich Museum. Cataloguing is now complete but much more work will need to be done researching dates, sites and deciphering some of the coded information on the specimen labels. Hopefully, an article will be forthcoming in the near future. Ian Wallace, the national recorder for Caddis Flies, originally asked me to look at the museum for information on the very rare caddis, Ironoquia dubia, which was recorded by Morley just once at his Monk Soham house. I also spent a very pleasant afternoon searching around the old moat at Monk Soham House in September 2007 but unfortunately no modern specimens were forthcoming.

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Two other species were recorded which are nationally regarded as having local status and which are probably at least notable within Suffolk. Firstly, Agrypnia pagetana was taken from the River Box in May 2009, this species has only one other record on the county database which was from Elveden in 1993. The second species was Holocentropus stagnalis recorded from a farm pond at Rushbrooke in May 2008. This species is regionally notable and very local in distribution. There are only three previous Suffolk records for the species, two prior to 1899 and one from Boxford in 2007.

The record of A. pagetana was made by a student on my identification course at Flatford Mill Field Studies Centre. The same student also made an interesting observation concerning one of the Hydroptilid species of caddis.

The minute larvae of this family construct an envelope or purse shaped case which is made of a secretion similar to spider silk which binds sand grains or algal threads into the shape of the case. Normally, these cases are found between small stones or in kick samples from a stream. Whilst turning large rocks to look for caseless caddis she noticed very large numbers of Hydroptilidae sp. cases stuck to the underside of the rocks. This would normally have indicated pupation taking place as most caddis make a sealed case to pupate in which is hidden away in crevices. However, under the microscope in the lab it could be seen that all the cases contained larvae.

Moreover all the cases were cemented with secretion onto the rocks by the thin edge of the envelope. They rather gave the impression of lines of dominos standing up on edge ready for a game. What advantage to this species was the unusual orientation of the case? Perhaps they were all preparing to pupate, maybe group pupation is a prerequisite for phased emergence, as occurs in certain mayfly species. As usual field observation leads to more questions to investigate. It is only possible to identify four of the 31 species of the tiny larvae of Hydroptilidae as many have yet to be bred out and described. An average larva is only 3 or 4 mm in length so you do need good eyes to spot the cases glued to a rock.

Adrian Chalkley Freshwater Invertebrate Recorder 37 Brook Hall Road Boxford Sudbury Suffolk CO10 5HS e-mail: aquatics@sns.org.uk Phone: 01787 210 140

Trans. Suffolk Nat. Soc. 45 (2009)