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Suffolk Natural History, Vol. 36

Freshwater Invertebrate Recording in 1999 As reported in the last transactions, 1998 broke a string of dry summers. During 1999 many months showed an above average rainfall and this has led to much better conditions, through the summer in particular, for freshwater invertebrates. Recording has continued throughout the year; though constraints on my time have led to the vast majority of this being done in the south of the county, with only a few trips to the north. No records have been forthcoming during the year from other naturalists, and I should like to renew my plea for these, especially from the north east of Suffolk. Any records, even of very common species, are welcome. In the brief report below I have picked out some of the species that have been notable during the last year, and concentrated on the less well known orders of invertebrates. During 1999 Ephemeroptera have done well, a greater variety of mayfly species being recorded in many locations than in previous years. Centroptilum luteolum, C. pennulatum, and Baetis vernus showing greater numbers in their usual locations and being taken in some new sites as well. Conversely Paraleptophlebia submarginata, was recorded in small numbers only and this continues it’s apparent decline over the last few years. Also I personally did not record Habrophlebia fusca during 1999, so although I did not look for it particularly I shall during the 2000 season. Higher water levels and flows seem to have favoured Caddis numbers, the common Trichoptera species being present in large numbers in many locations. The Hydropsyche, Polycentropus, and Hydropsyche species were particularly numerous and in some riffle areas of the rivers Box, Brett, Glem, and Lark it was impossible to obtain kick samples without obtaining a net full of Goera pilosa larvae in their distinctive stone ballasted cases. One particular species of caddis that I have not taken for a number of seasons is Agraylea multipunctata. I would welcome any news of the distinctive larvae of this species, which live in slow flowing or still water in a case resembling a silken purse with no sand grains, twigs or other material attached to it. In last year’s report I mentioned the reduction in numbers of certain species of water fleas. This last season has seen an improvement in the numbers of such species as Bosmina longirostris, Scapholeberis mucronata and Eurycercus lamellatus that I have taken in my recording trips. (Many will doubtless view the estimation of numbers of small creatures such as waterfleas from a pond or lake to be a highly subjective process. However these observations are based on counting catches obtained using a standardised method of sampling using a plankton net, allowing for some comparative analysis.) The Hemiptera Heteroptera seem to have had a fairly average year. There have been no new species to report for a few years now, although much more recording needs to be done in the North East of the county before we can accept that we have a definitive county list. The Water Scorpion, Nepa cinerea continues to turn up in many streams, even in times of flood where it can be found in grasses or other vegetation at the water margins. Hydrometra

Trans. Suffolk Nat. Soc. 36 (2000)


FRESHWATER INVERTEBRATES ORTHOPTERA OF SUFFOLK

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stagnorum, the water measurer is another common bug found in many new locations. Often it can be recorded on streams and is worth looking for on the stonework of bridges, particularly when the sun is shining. Other locations where it seems to be increasingly common are artificial garden ponds and ‘water features’. Hydrometra gracilenta is the much rarer species of water measurer and has not been found in Suffolk. However, there are old records from just over the border in Norfolk. This species is a cause of concern with only one modern record on the national database. So if anybody finds a Hydrometra with its eyes near to the centre of its head (instead of nearer to the base) please send it along to me at the address below. The Freshwater Invertebrate Survey of Suffolk website can be found at the same location as the White Admiral e-zine: http://www.fiss.purplenet.co.uk Adrian Chalkley, Freshwater Invertebrate Recorder 37 Brook Hall Road Boxford Sudbury Suffolk CO10 5HS E-mail Adrian@fiss.purplenet.co.uk

Trans. Suffolk Nat. Soc. 36 (2000)

Freshwater Invertebrate Recording in 1999  

Adrian Chalkley

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