The Aquatic and semi-aquatic Heteroptera of Suffolk

51

THE AQUATIC AND SEMI-AQUATIC HETEROPTERA OF SUFFOLK A D R I A N K. C H A L K L E Y To the general naturalist, casually observing the freshwater environment, the aquatic and semi-aquatic bugs are familiar insects. Skating across the surface, hanging f r o m it or jerkily swimming below, they are a common sight from the banks of rivers, streams, lakes or ponds. They are a relatively easy group to study due to the distinct ecological niche they occupy and yet no comprehensive description of the Suffolk fauna has ever been written, indeed very few individual records have been published.

This survey was instigated with the aim of eventually providing such a description. In my previous articles, (SNS Trans. 30 & 32) I have presented some of my early records for the group. Here I give an interim account of the present knowledge of the distribution of species and outline the future direction of the survey which will, I hope, lead to the publication of an atlas for the county.

Over 700 records have so far been entered onto the Computer database from 188 sites in Suffolk, some 200 more await entry. Data have been recorded on 46 species f r o m a total British list of 61. Of these, 37 are confirmed by modern records, a further 9 only exist as archive data.

As well as my own records recent data have been collected from the National Rivers Authority and from a small number of individual recorders.

Archive records have been obtained from the Field Studies Council at Fiatford Study Centre and from the records centre at Ipswich Museum.

Methods Düring this survey no overall attempt was made to obtain quantitative measurements by rigidly defining sampling time or volume. The general approach was to sample all accessible micro habitats at a site until it was judged that all the common species had been obtained from each. Freshwater habitats of all kinds were sampled using the following equipment and methods.

•

Hand-held, robust pond nets to sample in shallow water and from accessible areas of the bank.

•

Weed grabs and hooks to bring weed samples in from deep or inaccessible water or to drag mats of algae from the centre of a pond or lake.

•

Plankton nets to trawl through the water, grazing the substratum or the tops of weed banks to 'put up* bugs, particularly corroxids, which were then captured in the net.

•

Plankton nets and band held pond nets to trawl semi-submerged across the water surface, particularly along the edge of reed beds, and capture surface dwelling bugs.

•

Drift nets anchored to a stream bed to capture invertebrates washed from stones and the substratum in general.

Trans. Suffolk Nat. Soc. 34

(1998)

52

Suffolk Natural History, Vol. 34

In most cases voucher specimens have been taken as the majority of aquatic heteroptera are difficult or impossible to identify in the field without the use of a microscope.

Recording has taken place every year since 1985, from early spring to late autumn. Occasional samples were taken in winter as I have found that several species are still active in mild weather, particularly at night. Little work was attempted in June and July due to the almost complete absence of the adults of most species whilst the unidentifiable nymphs complete their development.

Future Aims a

To search for target species whose status or distribution needs confirming.

b

To complete recording from at least every 10km Square in Suffolk. A complete tetrad survey will not be attempted as I am virtually the only recorder. Only a small number of squares remain with no records, at least for riverine sites.

c

To increase the number and ränge of still water sites. Ponds and lakes at present only make up 14% of the total number due to greater ease of access to rivers.

d

Complete coverage of the under-recorded coastal strip.

Table 1: Target Species (Those in bold print are known only from archive records.)

Mesovelia furcata Hebrus ruficeps Microvelia pygmaea Microvelia reticulata Gerris argentatus Gerris gibbifer Gerris thoracicus Gerris lateralis

Notonecta obliqua Corixa dentipes Hesperocorixa moesta Arctocorisa germari Sigara stagnalis Sigara selecta Sigara semistriata

Results There now follow preliminary accounts for all species occurring in Suffolk.

These are generally arranged in the order adopted by Savage and common names have been given where they exist. As the survey progresses any significant new data will be available via the internet on the Freshwater Invertebrate Survey of Suffolk web site.

There is still a considerable amount of work to do on this group and comments or records, old and new, are most welcome.

Trans. Suffolk Nat. Soc. 34 (1998)

AQUATIC HETEROPTERA

53

Semi-aquatic, Surface Bugs Mesoveliidae Mesovelia furcata Mulsant & Rey, 1852 2 recent records The records of this species are from a ditch near the RSPB reserve at Minsmere and a site near Boxford. The first is very much a coastal Situation with the end of the ditch only a few meters from the seashore, the second a lake fed by a typical small Suffolk stream. Both habitats are well vegetated with clear water and very good growth of floating plants. Along with other minute bugs it is doubtless under recorded. At only 3 mm long and living on floating Vegetation it is hard to see unless deliberately searched for. A useful technique adopted by Bernard Nau, (Peter Kirby, pers. comm.) is to capture the mats of algae one normally steers the pond net around, Mesovelia can occur in large numbers on these.

Hebridae (sphagnum bugs) Hebrus ruficeps Thomson, 1871 1 archive record In 1942 this species was recorded at Thelnetham Bog near the Little Ouse on the Norfolk Border. It was then described as 'the commonest bug at the site.'

No records have been made since however and a thorough search of the location is needed. There is a difference of opinion as to its habitat preferences.

Some authorities say it is only associated with Sphagnum (Brown, 1948 & Kirby, 1992) but it was found in brown mosses beside non acid pools or lakes in Northern Ireland (Nelson, 1995) and similarly wider preferences are reported elsewhere (Dolling, 1991). So whilst it is possible that the bug does not now survive in Suffolk we cannot write it off completely.

Hydrometridae (water-gnats or water-measurers) Hydrometra stagnorum Linnaeus, 1758 45 recent records This, the commoner of the two species of water-measurer, occurs all over East Anglia. In Suffolk it seems to be associated equally with rivers or lakes, particularly amongst reed beds on slow flowing sections of some of our larger rivers. Often found out of water as well, it is worth looking out for Hydrometra on any nearby stonework or concrete, particularly on sunny days. Short grass on the river bank and small puddles are also good locations to search. I have a stream running through my own garden and can always find Hydrometra specimens on the stream bank, on the stone walls and on the concrete bridge over the water. This is especially true at night when greater numbers are visible by torch-light in all locations. Hydrometra is a slow moving bug which relies on true Walking over the surface film, unlike its faster cousins of the Gerridae and Velidae.

Veliidae (water-crickets) Velia caprai Tamanini, 1947 52 recent and 3 archive records Although there are two species of Velia in Britain only the commonest appears

Trans. Suffolk Nat. Soc. 34 (1998)

54

Suffolk Natural History,

Vol. 34

to be present in Suffolk. Our records, at present, are concentrated in the west of Suffolk, along the river Lark and tributaries of the Stour, with the addition of one or two coastal streams. However, I expect that there will be more sites yet to be found in the under recorded coastal strip.

6

7

8

9

0

1

2

3

4

5

In my spring-fed garden stream Velia often occurs in large swarms reminiscent of gnats, constantly swirling over the surface. At other times almost none can be seen as they hide up under rocks and in Vegetation, flattening themselves into tiny spaces. They are more often absent during the day than at night, but this is not always so as in summer they have a tendency to congregate in sunlit patches of surface water. Both Velia and Hydrometra seem to bask in the sun more than Gerris.

In upland areas of Britain Velia may also frequent small pools but here in Suffolk they have only been found in running water. The prowess of Velia on flowing water cannot be doubted once you have seen it, as I have, skating around with impunity a few centimetres from the edge of waterfalls on mountain streams. It maintains both speed and position in these conditions by judicious use of chemicals called 'Surfactants' which destroy the surface tension of the water. These work in a similar way to a drop of washing up liquid in a bowl of greasy water, and the retreating surface tension pulls the water-cricket across the surface at high speed.

Trans. Suffolk Nat. Soc. 34

(1998)

AQUATIC HETEROPTERA

55

Microvelia pygmaea Wingless male from a pond in Theberton Woods Length 1.6 mm

Microvelia pygmaea Dufour, 1833 1 recent record Microvelia reticulata Burmeister, 1835 6 recent records The relatively few records for the subfamily Microveliinae show M. pygmaea in the eastern, coastal strip of the county and M. reticulata in the south and west. However, these are very small insects and doubtless need much more work to get a true picture of their distribution. Here in Suffolk, as elsewhere, they are particularly numerous amongst stands of emergent Vegetation and also seem to frequent mats of algae and other floating leaves, particularly float grass. Most of the current sites are small ponds containing large amounts of leaf debris on the bed, particularly in wooded areas. There are also two records for M. reticulata on dykes alongside the river Stour at Fiatford in the 1950s and at one similar site by the River Lark in 1996.

A third species, Microvelia buenoi umbricola, has been recorded in a small number of sites in Norfolk but not as yet from Suffolk.

Gerridae (pond-skaters or water-striders) The pond-skaters row their way across the surface film using their powerful, elongate middle legs. This rowing action achieves a level of locomotion midway in speed between that of Velia and Hydrometra, but any naturalist who has attempted to net Gerris will have realised that this is still very efficient indeed.

Gerris argentatus Schummel, 1832 3 archive records G. argentatus is considered rare (Savage, 1989) and has not yet been recorded during the survey. The archive records are from Barnby and Oulton Broads near the Suffolk - Norfolk border in 1911. This is the most likely location to rediscover the species since little work has been done in that area. The other record is from 1956 on the Stour at Fiatford. At 6.5 - 8 mm long it is one of our smallest pondskaters and is quite easily distinguished in the field by patches of silvery hairs at the rear of the disk on the pronotum.

Trans. Suffolk Nat. Soc. 34

(1998)

56

Suffolk Natural History, Vol. 34

Gerris gibbifer Schummel, 1832 1 recent record In 1997 this species was recorded for the first time on a cool, spring fed pond at Hayhill allotments in Ipswich. This is, once again, a rare lowland species whose typical habitat is small ponds and pools with good surface cover and organic matter. A medium sized gerrid with a black disk, the yellow line on the sides of the pronotum is confined to the rear portion making identification in the field quite easy.

Gerris thoracicus Schummel, 1832 1 recent and 1 archive record In Ireland G. thoracicus is often found in coastal locations, both in pools above the splash zone on rocky shores and those on saltmarshes. It also is common on inland pools and ponds that are recently disturbed. (Nelson, 1995) In Suffolk the only modern record for G. thoracicus is from a series of three ponds the Forestry Commission has recently constructed on the River Tang, to the north east of Ipswich. Here the river flows through a bed of Red Crag over clay a short way from the coast. G. thoracicus occurs here with G. lacustris on ponds that are very well vegetated with large amounts of Potamogeton and dense stands of reeds, both at the pond fringes and along the stream between the ponds.

These ponds fit the habitat niche, described by Nelson, of recently disturbed sites and it will now be necessary to search nearby coastal locations for other colonies.

Gerris lacustris Linnaeus, 1758 29 recent records Certainly the commonest Gerrid in Suffolk, and probably in Britain as a whole, G. lacustris occurs in as many pools, ponds and lakes as streams and rivers. A medium sized pond skater it is the species most naturalists will know from their garden ponds. It has very good dispersal abilities and quickly colonises new water bodies.

Gerris lacustris Male specimen from my garden pond in Boxford.

Length 8-10 mm

Trans. Suffolk Nat. Soc. 34 (1998)

57

AQUATIC HETEROPTERA

Gerris lateralis Schummel, 1832 1 archive record A J. Hopson found G. lateralis in a pond in Leavenheath in 1958. This predominantly northern species would seem a surprising find in Suffolk, but fairly recent records (Nau, 1984) confirm its presence in Bedfordshire and Cambridgeshire so future finds remain an intriguing possibility.

Gerris odontogaster Zetterstedt, 1828 3 recent and 3 archive records This is the second most common gerrid in the county database but there are far fewer records than for G. lacustris. This is probably due to its preference for small lakes and pools and the fact that at present these only represent 14% of the surveyed sites.

However, the three archive sites have survived as continuously good habitats, yet the species has disappeared from them. Otherwise we have one site right on the coast where you can taste the salt spray, a Cluster of ponds near my home in the south west, and one site on the River Lark in the north west.

The two toothed projections on the male abdomen make this an easy species to identify in the field. As I have particularly searched for the species whenever visiting suitable sites it seems unlikely to be as common in Suffolk as reported elsewhere (Nelson, 1995 & Savage, 1989).

Tube Breathing, Non Swimming Bugs - Nepidae Nepa cinerea Linnaeus, 1758 (water-scorpion) 39 recent records The map for the water scorpion shows a wide distribution across Suffolk.

Nationally, Nepa seems to have a preference for moderately eutrophic and mesotrophic lakes and ponds but in Suffolk it also forms large colonies in streams with little or no Vegetation present. This lack of Vegetation echoes findings in Ireland (Nelson, 1995) although Nepa does not utilise flowing water there. This is contrary to earlier reports (Southwood & Leston, 1959) which stated that weeds were always present.

Nepa orverea • Recent records

c

TG

r^-i

V -I

\\

iMt

3 f

b

V

Y,\ JO. VO

TL 6

vj

>

y

7

8

1

Nepa cinerea Hol Brook, Boxford.

Length 17.0-23.0 mm

TM

-rtli 2

3

4

5

Trans. Suffolk Nat. Soc. 34

(1998)

58

Suffolk Natural History, Vol. 34

My own garden stream is a typical flowing water site for Nepa. Here the water flow is fairly slow for much of the year but does, at times of high rainfall, deepen to 60 cm or more and flood down at a tremendous rate which tends to clear the stream bed of the usual thick winter deposit of oak leaves and silt. In autumn and early winter Nepa is found predominantly in the leaf litter yet somehow avoids being washed away in a flood. Visiting the stream at night with a torch reveals that Nepa is as often to be found out of the water as in it.

Large numbers are then in leaf litter on the banks, crawling over the stone walls or on rocks above a pond on the bank - often at a distance of 2 or 3 meters from the water. Nepa may therefore be able to avoid flooding by leaving the water, it moves surprisingly quickly at times, and the water usually rises relatively slowly here.

When out of the water it is able to walk on four legs whilst actively predating small invertebrates on the bank, holding the fore legs out in front of it to capture prey. Its movements seem somewhat erratic and I've watched specimens clamber laboriously up and over large rocks above the waterfall from my pond, only to go blindly off the edge and fall onto stones by the stream. The particular shape of the insects often means that this results in a landing on their backs and they have some difficulty in righting themselves.

Due to the flatness of their bodies water tension then holds them to the stone and there ensues a minute or two of scrabbling with the middle and hind legs, first on one side and then the other. This results in swinging the body from side to side until a piece of moss or a crevice can be grasped to lever the insect over.

When mating occurs there are often up to five individuals involved with a pile of insects on top of each other. Presumably there is a female beneath and several males above. Again this is an area worth investigating further in future.

The question of flight in Nepa has been debated for some time in the literature. Certainly the wing muscles of adults vary considerably in the extent of their development. In other species of Heteroptera this is often a seasonal Variation and a precursor to mating and colonisation of other sites. However, in Nepa development of the wing musculature does not seem to show seasonal patterns and I can find no published records of observed flight. Nepa was the first insect to appear in a new pond I built many metres from my stream, this was possibly due to flight as it seemed too far for it to crawl. It appeared in the pond overnight, although the allied species Ranatra certainly flies in the day, as outlined below.

Ranatra linearis Linnaeus, 1758 (water-stick insect) 8 recent records Ranatra linearis is present in a few sites in Suffolk, though always in small numbers. In many ways the habitat requirements are similar to Nepa, at least in the niche it occupies in still waters, however I have only one record from flowing water. This was a typical Suffolk lowland river; wide, deep and slow flowing with Ranatra inhabiting areas of floating grass at the bank and it was likely to have arrived from a garden pond close by.

Ranatra certainly does fly however. Joan Hardingham saw a specimen of Ranatra fly in and land on black plastic, laid for strawberries, on one of the hottest days of summer in 1996 (SNS Transactions 32, 1996). I imagine that

Trans. Suffolk Nat. Soc. 34 (1998)

AQUATIC HETEROPTERA

59

Ranatra linearis length 30-35 mm Nepa flies in much the same way, though I should like to know more about the influences that make them fly and perhaps the weather patterns that prior to this produce changes in the development of the flight muscles. The only reference to this I have been able to find cites receding water levels as the stimulus (Southwood & Leston, 1959).

Actively Swimming Bugs Naucoridae (saucer bugs) Ilyocoris cimicoides Linnaeus, 1758 12 recent records In the early years of the Century Ilyocoris was considered by naturalists to be purely a coastal species but I have found it to be widespread in the west of the county as well, though absent so far from central Suffolk. My first encounter with it was a specimen dead in a shallow puddle on an Essex school playground, presumably it dived in at night and died.

Ilyocoris cimicoides Skating Pond, Boxford.

Length 11-15 mm

Trans. Suffolk Nat. Soc. 34

(1998)

60

Suffolk Natural History, Vol. 34

/. cimicoides, the only British species of this family, occurs mainly in ponds, very occasionally in lakes but not in rivers. In the Suffolk sites where it is present it usually occurs in large numbers. At times I've found two similar ponds in close proximity, one of which had a large colony of Ilyocoris and the other which had none. It may therefore have very specific habitat requirements.

This is probably for a largish pool with a bottom of organic mud and or plant detritus, though there are some sites that contradict this. It seems to be able to maintain its presence in a favoured pond over a number of years, yet is able to colonise new sites when conditions are right. Dr Peter Kirby has found a similar Situation in Peterborough for saucer bug distribution (pers. comm.).

Notonectidae (backswimmers or water-boatmen) Notonecta glauca Linnaeus, 1758 61 recent records

0

1

2

3

4

5

Notonecta glauca Length 14-16 mm

Notonecta maculata Fabricius, 1794 13 recent records Notonecta marmorea viridis Delcourt, 1909 10 recent records Notonecta obliqua Gallen, 1787 3 archive records Three of the four British species of Notonecta continue to be recorded in Suffolk with N. glauca easily the most widespread and common. Although N. glauca has been reported as absent from man-made reservoirs in Ireland (Nelson, 1995), it has been recorded from these habitats in Suffolk.

N. maculata is widespread in Suffolk, although nowhere is it as common as N. glauca, and its habitat preference is contrary to published accounts which restrict it to ponds (Savage, 1989). Here it occurs in small and larger rivers and in small ponds, but not as far as I know in lakes. Both eutrophic and mesotrophic conditions seem to be tolerated though the population density is

Trans. Suffolk Nat. Soc. 34 (1998)

61

AQUATIC HETEROPTERA

often lower in eutrophic ponds. This is possibly due to its need to attach its eggs to a hard substratum, which may be more difficult to achieve in these conditions. All other Notonecta species insert eggs into plant tissues.

N. marmorea viridis turns up sporadically in widely separated sites in the south of the county. It is present in the Stour and its tributaries as well as in ponds. These river sites again contrast with published data citing this as strictly a pond species, but they are similar to the sites found for N. maculata. The name viridis does not reliabiy indicate more green colouration than any other species is likely to have and I have also found the markings along the hemielytron membrane base may be weak and superficially like N. glauca.

However, the sharp anterior shoulders on the pronotum give a clear identification which can be used in the field.

N. obliqua was found at two sites on the Stour in the 1950s. It seems to have always been rare in this region (Savage, 1989) and will remain a target species for the survey.

Ptoa leachi

r

i

\

5

J

X 11

vj lX £

T i

i

;

•Y - y TL

W v W M M

•

7

4T

TG

• Recent records n Pre-1ftflOrerrrri«

_ x 8

7

3

^

&£

-

J

S

C S

Ujt

s

• s

TM

it

0 1

% I

x,

$ t

Plea leachi Length 2-3 mm

Pleidae Plea leachi McGregor & Kirkaldy, 1899 26 recent records In his 1989 key to the group Savage included Suffolk in his Midland area. He reported Plea as present in Essex but stated that it was absent from the Midlands, whilst it was occasional in Ireland. However, it has not recently been recorded in Ulster (Nelson, 1996) and it is present in Suffolk. To what degree these anomalies indicate a change of ränge for Plea or a lack of previous records is unclear. It is certainly an occasional species here but appears to be widespread in the south and north west of the county.

It has been taken in floating and submerged Vegetation in both large and small rivers and it may also be found in a variety of still waters, including small eutrophic ponds at the edge of woods or on farms. A useful method to find Plea is to use a plankton net trawled over the top of clumps of submerged Vegetation.

Trans. Suffolk Nat. Soc. 34

(1998)

62

Suffolk Natural History, Vol. 34

Corixidae (lesser water-boatmen) Micronecta poweri Douglas & Scott, 1869 8 recent records Micronecta scholtzi Fieber, 1847 11 recent records Both these species have been recorded only from the west of the county and are obviously under recorded because they are only around 2mm long. They do occur together in Suffolk but so far this is only in rivers, though M. scholtzi also turns up in ponds as well as lakes.

M. poweri has a preference for stony river beds and the sites where it has been found are typical East Anglian rivers with large areas of flint and other gravels on top of the clay bed. In August 1993, at two of the sites with both species, I found colonies with approximately the same features; a male to female ratio of 1:2 and M. poweri making up around 25% of the population.

Sometimes I have seen a very large Micronecta population in amongst the flints on the river bed so that when disturbed they first appeared like a swarm of water fleas, except for a rather smoother locomotion. This has been in June or July. The numbers found in ponds or lakes have never been as high as this, except for one large lake at Highwoods Country Park in Colchester in 1992.

Here M. scholtzi was the most common water bug and was present in such large numbers that every net sweep was covered in them, all around the bank.

However, a subsequent rise in the populations of both fish and anglers and a related decline in aquatic Vegetation has ruined that particular lake for invertebrates. All populations have crashed and Micronecta appears to have disappeared completely.

Cymatia bonsdorffii Sahlberg, 1819 3 recent records

Cymatia bonsdorffii Stewards Barn Pond, Leavenheath.

Length 5.5-6.5 mm

Trans. Suffolk Nat. Soc. 34 (1998)

i AQUATIC HETEROPTERA

63

Cymatia coleoptrata Fabricius, 1776 10 recent records Both British species of Cymatia are to be found in Suffolk, they are very occasional here, widespread and usually to be found in small numbers. The only exception to this I know of was an occasion on Dec 3Ist 1984 when I found a swarm of them in the stream in my garden. This was at lOpm with an air temperature of -2 degrees Celsius and the water at about 1 degree. The stream bed above the stones was covered with a cloud of Cymatia which showed up very clearly in torchlight. They were a fairly equal mix of C. bonsdorffii and C. coleoptrata. Within a few days this had dwindled to a few individuals. Since then, in the stream and the spring fed lake above my garden, I have only occasionally recorded individuals of either species. The reason for this gregarious behaviour remains a mystery as mating or protection against fish predation both seem unlikely causes at that time of year.

C. bonsdorffii has only been recorded from two Suffolk sites, the other only a couple of miles from my home and again in Company with C. coleoptrata.

The commoner species here is C. coleoptrata but neither has been found in central or eastern Suffolk as yet. These bugs are superficially like the related Corixinae but are distinguishable in the field by their cylindrical, almost brush-like fore tarsi. Unlike most of the Corixidae they are predators of small invertebrates rather than herbivores.

Callicorixa praeusta Fieber, 1848 16 recent and 3 archive records

64

Suffolk Natural History, Vol. 34

My first record for C. praeusta was in 1993, where it appeared at three sites I had been working at for a number of years. 1993 seems to have been a good season for C. praeusta in my part of Suffolk and it was also found in a number of neighbouring areas in 1994. Records have declined since then although I have located a Single record by the National Rivers Authority from 1991 and three from the 1950s at Ratford Mill Study Centre.

This is cited as predominately a lake species, also recorded from ponds.

Whilst this is born out by most of the Suffolk sites C. praeusta has been found at sites on the Stour and Deben. Thus far, however, it appears to be mostly confined to the south of the county.

Corixa dentipes Thomson, 1869 1 recent record Corixa panzeri Fieber, 1848 6 recent records Corixa punctata Iiiiger, 1807 43 recent records Corixa spp. are the largest of the Corixidae and three of the five British species occur in Suffolk. C. punctata is the commonest species and occurs in a wide ränge of sites from overgrown and almost silted out farm ponds, through to large lakes. However, whereas in many areas its habitat ränge excludes rivers the opposite is true in Suffolk. Both small, slow-flowing streams over flint beds and larger, deep rivers such as the Lark and Stour which have muddy bottoms are habitats here. I suspect it is present all over the county, although there are few records from central Suffolk as yet.

C. panzeri is an infrequent find here and, apart from one record, the sites where it has been found are all in the east, not far from the coast. The exception was a complex of large lakes at a holiday village in Breckland, well inland in the north western corner of the county. That record was from 1993 and it has not been found there since. I expect that further surveying along the coast will produce more records for this species.

The Single record for C. dentipes is from the river Stour in 1991. This species is listed as rare everywhere in Britain and it will be a target species for the survey in the future.

Hesperocorixa linnaei Fieber, 1848 8 recent records Hesperocorixa moesta Fieber, 1848 1 archive record Hesperocorixa sahlbergi Fieber, 1848 43 recent records Suffolk records for H. sahlbergi indicate a southern and eastern distribution with another Cluster of records up in the north west. The species is typical of base-rich sites with high amounts of organic material. It occurs here in small lakes and also much smaller ponds. These include newly-constructed farm ponds on 'set aside' land, old but recently cleared and deepened pools in

Trans. Suffolk Nat. Soc. 34 (1998)

AQUATIC HETEROPTERA

65

woods and even, in three cases, old, neglected woodland ponds. These last were heavily shaded, filled with rotting leaves and branches and smelled strongly of hydrogen sulphide bubbling up from the mire. A couple of the farmland ponds were old clay, brick or gravel pits of a small size. H. sahlbergi is also recorded from river sites in Suffolk. However, these were very slowflowing sections of lowland rivers which, in the reed beds at the sides, approximate to an extent to still water.

H. linnaei is recorded much less frequently, from the south and west of the county. Savage suggests its habitats are equally lakes and ponds. Here in Suffolk it is recorded from large, old farm ponds but from no lakes as yet. In addition a stream feeding Easton Broad, which is a coastal site, and two sites on tributaries of the River Stour are unusual records for the species. Both river sites were at slow-flowing locations in deep pools.

Our only record for H. moesta dates from 1933 at Oulton Broad on the Norfolk border. Rare everywhere in Britain (Savage, 1989) this will become another target species for the survey.

Arctocorisa germari Fieber, 1848 1 archive record Predominately a lake species considered by Savage to be rare across South East England, I have never found A. germari but I came across one curious record dating from 1961 on the Stour. This was a record determined by T. T. Macan who wrote the original FBA key to this group. Whilst it is quite likely to have disappeared in the intervening years this will again become a target species.

Sigara concinna Fieber, 1848 5 recent records Sigara scotti Douglas & Scott, 1868 2 recent records Sigara striata Linnaeus, 1758 3 recent records The species above have only been recorded from a few sites in Suffolk. All are considered rare in South East England.

Sigara dorsalis Leach, 1817 94 recent records In Suffolk S. dorsalis is not only the commonest species of Sigara but of all the aquatic bugs. It is present in a large number of smaller ponds, with the exception of woodland pools, as well as the expected lakes. About 80% of the records come from rivers and streams.

Sigara distincta Fieber, 1848 14 recent records The records for S. distincta come just about equally from large, mildly eutrophic ponds and medium lakes, or from rivers. In rivers they were often found on bare mud or stones on the bed or amongst algae on the concrete walls of Channels, bridges, sluices and similar structures. All records so far are from the south and west of the county.

Trans. Suffolk Nat. Soc. 34 (1998)

66

Suffolk Natural History, Vol. 34

Sigara falleni Fieber, 1848 54 recent records This species is wide-spread across the whole of the county. It is found in large lakes and also from moderate sized ponds. From other surveys there is empirical evidence that it readily colonises new sites (Nelson. 1995), though this runs counter to earlier reports (Southwood & Leston, 1959). About 8% of my sites are newly dug ponds on 'set aside land' and one is a series of totally artificial lakes lined in Butyl with a covering of clay. As seems to be a common theme, I have also found it inhabiting a number of the rivers widely spread across Suffolk.

Sigara fossarum Leach, 1817 10 recent records The relatively few records of S. fossarum from Suffolk are widely spread over the county and include two lakes, a waterworks reservoir, some small ponds and some rivers.

Sigara limitata Fieber, 1848 7 recent and 1 archive records Rare throughout Britain (Savage,1995), S. limitata has been found in seven locations. Four of these were typical still-water sites and the three that were in rivers were well vegetated with good stands of submerged as well as emergent Vegetation. One of the sites lost significant amounts of submerged Vegetation the season after S. limitata was recorded there, and it quickly vanished.

Sigara nigrolineata Fieber, 1848 13 recent and 4 archive records The records for S. nigrolineata in Suffolk are split, with about half the sites in still and half in flowing water. Only one of the still water sites was a lake, or rather the system of lakes at the Center Parcs holiday village in Breckland. The species seems to have arrived at this site around 1993 and has been present in small numbers ever since, I last found it there in October 1996. Most of the other sites were ponds, particularly those in woods, and were fĂźll of leaf litter.

This fits in with the known habitat preferences of S. nigrolineata for polluted ponds (Nelson, 1995). The rest of the ponds had been recently cleared and improved as conservation exercises.

Sigara semistriata Fieber, 1848 2 recent records Of two records for this species one is from a small stream and one from a waterworks, both are in coastal Suffolk but both are received records and I have no other knowledge of the locations.

Sigara venusta Douglas & Scott, 1869 5 recent and 1 archive record The records for S. venusta make an intriguing arc across south eastern Suffolk.

Although Savage indicates that this species occurs in ponds as frequently as rivers, all Suffolk records are from rivers. Despite the present bias in the data towards rivers all the S. venusta records are near to ponds and lakes which have been surveyed.

Trans. Suffolk Nat. Soc. 34 (1998)

AQUATIC HETEROPTERA

67

Sigara lateralis Leach, 1817 9 recent and 4 archive records S. lateralis is found at brackish sites and eutrophic ponds across Britain as a whole. A very occasional species in Suffolk, about half of the records are from the coastal part of the county, although these are freshwater and not at all brackish. The other sites are old and very eutrophic ponds which are well inland. Archive records are from Shingle Street and from ponds and dykes around Fiatford.

Sigara stagnalis Leach, 1817 6 recent and 1 archive record Sigara stagnalis is tolerant of the highest salinity and has a predominately coastal distribution in Britain. It occurs in Essex, mostly from brackish stretches of rivers and streams close to the normal tidal limits, but with one or two additional records from ponds and lakes. The position in Suffolk should eventually prove to be similar. The only Suffolk archive record dates from 1957 at Shingle Street. There are also six slightly doubtful records from sites on the River Stour and its tributaries between 1989 and 1992. These sites are freshwater, although some are close to the normal tidal limit, but the whole area will need checking to definitely establish the presence of S. stagnalis.

Sigara selecta Fieber, 1848 2 archive records Together with S. stagnalis this is a species associated with brackish water.

Recorded twice at the coast in the 1950s it is still likely to occur in some of the marshes and dykes in this area.

Other Species Of the fifteen species on the British list which have never been recorded from Suffolk there are six that I consider most likely to provide future additions to our lists. All are cited as rare in this region.

Table 2: Possible Additions to the Suffolk List.

(Species with bullets have been recorded from Norfolk.)

Hydrometra gracilenta Horvath, 1899 Microvelia buenoi umbricola Drake, 1920 Velia saulii Tamanini, 1947

Gerris paludum Fabricius, 1794 Micronecta minutissima Linnaeus, 1758 Hesperocorixa castanea Thomson, 1869

References Brown, E. S. (1948). A contribution towards an ecological survey of the aquatic and semi-aquatic Hemiptera-Heteroptera (water bugs) of the British Isles; dealing chiefly with the Scottish Highlands and South East England.

Trans. Soc. Brit. Ent. 9: 151-195.

Dolling, W. D. (1991). The Hemiptera. Oxford University Press, Oxford.

Trans. Suffolk Nat. Soc. 34

(1998)

68

Suffolk Natural History, Vol. 34

Kirby, P. (1992 ). A review of the scarce and threatened Hemiptera of Great Britain. UKNature Series No. 2. JNCC, Peterborough.

Nau, B. S. (1984). Heteroptera Study Group Newsletter No 3, Institute of Terrestrial Ecology, Cambs.

Nelson, B. (1995). The distribution of aquatic and semi-aquatic Heteroptera in Northern Ireland, Irish Biogeographical Society Bulletin 18(1): 66-130.

Dublin.

Savage, A. A. (1989). Adults of the British aquatic Hemiptera Heteroptera; Freshwater Biological Association. Scientific Publication No. 50.

Ambleside.

Southwood, T. R. E. & Leston, D. (1959). The land and water bugs of the British Isles. Warne, London.

A. K. Chalkley 37 Brook Hall Road Boxford Sudbury Suffolk.

C 0 1 0 5HS E. Mail 100776.1221@Compuserve.com The Freshwater Invertebrate Survey of Suffolk can be found on the world wide web at: http://ourworld.compuserve.com/homepages/A_C_Chalkley/ The European Eared Leafhopper, Ledra aurita Linnaeus (Hemiptera: Homoptera: Cicadellidae) in Suffolk This curious-looking insect, measuring about 16mm long, is olive-green in colour and gains its name from the two flat thoracic projections somewhat resembling ears. It is sometimes illustrated in the literature from dead speeimens, which have usually lost their greenness and faded to a yellowish brown. The species is, however, the only representative of its group to be found in Europe and is considered to be unmistakeable. It is generally associated with oaks. In 1997, three adult speeimens flew to mv light here at Seiborne in Hampshire on 12 August and a further example on 20 August. They were jumping around the light-trap quite vigorously but were sluggish between leaps. Alerted thus to this species, I was later looking through my collection, where I found a speeimen I had taken in Stowmarket at light on 22 August 1959, but which had remained unidentified. In the autumn I was speaking to Martin Sanford, who kindly referred me to Claude Morley's note on L. aurita (Trans. Suffolk Nat. Soc., 5: 37). Claude regarded the insect as everywhere rare, occurring in only nine English counties and seen by him but eight times in half a Century. The Stowmarket speeimen, it appears, may have been the second reported from West Suffolk. In an outline life-history, Morley remarks that imagines are to be seen between "3-8 July only". It will be noted that my Stowmarket singleton and the Seiborne quartet all arrived in the period 12-22 August.

I would welcome any comments on the development dates and occurrence of this leaf-hopper. Alasdair Aston

Trans. Suffolk Nat. Soc. 34 (1998)