Essex Glow-worm Survey




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Contents





Page

Summary

1







1.0 Introduction

2







2.0 Method

2







3.0 Results

3

3.1 Recording coverage

3

3.2 Distribution of L. noctiluca in Essex

4

3.3 Declines

5

3.4 Transect recording

6

3.5 Nature reserves

7

3.6 Habitats

7

3.7 Lighting

8

3.8 Management of sites

9







4.0 Discussion

9

4.1 Conservation

11

4.2 Transect monitoring

12

4.3 Site management

12







5.0 Conclusion

12







Acknowledgements

13







References

13
















Tables










1: Two week periods for each of the three transect walks

3







2: Details of L. noctiluca monitoring at each site

7







3: L. noctiluca females observed under different lighting conditions

9







Figures










1: Recording coverage in 2001

4







2: Distribution of L. noctiluca records since 1992

5







3: Frequency of counts

6







4: Percentage of L. noctiluca females in different habitats

8







Appendices










1: Grid references for sites surveyed in 2001

14







2: Sites at which L. noctiluca were observed in 2001

16







3: Sites at which L. noctiluca were recorded from 1992 to 2000

17


Summary

A countywide survey of the Glow-worm Lampyris noctiluca L. (Coleoptera: Lampyridae) was undertaken in 2001, which aimed to ascertain the current distribution of this species. The survey involved establishing a transect at a potential or known site and walking it three nights during the summer. In addition, casual observations of L. noctiluca were accepted so that the Essex distribution could be determined. The survey indicates a widespread but localised distribution for L. noctiluca, although this species is not as rare as previously thought, with observations having occurred at 43 sites since 1992.


Numbers of L. noctiluca observed on the transect walks were mostly low. The highest count of the survey occurred at One Tree Hill, where 76 individuals were observed. One Tree Hill is part of Langdon Hills Country Park, near Basildon and is of great importance for L. noctiluca in Essex, as 37% of individuals recorded during the transect walks were observed at this site. The preferred habitats were meadow and scrub, predominantly in dark, unlit areas. Few L. noctiluca individuals were recorded near any form of artificial lighting. The status of this species in Essex appears to be relatively secure in the short-term, although development pressure, pollution and neglect of sites are the main long-term threats.


  1. Introduction

For many centuries the Glow-worm Lampyris noctiluca L. (Coleoptera: Lampyridae) has inspired naturalists and poets due to the pale green glow which is emitted by the adult female on warm summer evenings. Leutscher (1974) fondly recalls his camping days in Epping Forest when specimens were collected and hung in jam-jars inside tents, with the light emitted apparently strong enough to read by. The female’s glow is produced via a complex series of chemical reactions and is used to attract the flying adult male. L. noctiluca is primarily an insect of unimproved grassland and other habitats such as old woodland (Tyler 1994).
In Essex, L. noctiluca has been described as rare (Corke 1984), with the county recorder having records for only 13 sites (Samuels pers.comm.). Many of these records are extremely old and give very imprecise information on the exact location of the observed colony, for example, TM02 Colchester 1903. The apparent rarity combined with the possible under-recording of this species in Essex led the authors to organise a countywide survey of L. noctiluca in 2001. The main aims of the survey were to ascertain the current distribution and main strongholds for L. noctiluca in Essex.
2.0 Method

Survey participants were required to count glowing females along a chosen transect route on three occasions during July and August 2001. In addition, any casual records of L. noctiluca since 1992 were accepted so that the distribution of this species could be more accurately ascertained. The survey was widely publicised in various newspapers throughout the county and on BBC Radio Essex. Leaflets were distributed to nature reserve visitor centres and a press release was posted on the Essex Wildlife Trust website and the British Glow-worm page www.glowworms.org.uk. Although the survey therefore involved participants with limited or no entomological knowledge, the distinctive nature of the adult females minimised the likelihood of identification difficulties.
With appropriate guidance, survey participants were asked to select a suitable site at which to establish a transect route, either within an area where L. noctiluca had been observed before or at a new location where habitats such as unimproved grassland were present. Survey participants were initially required to visit their site during daylight hours to determine the transect route, to produce a sketch map of the area and to note habitat types and management regimes.
A transect of at least 100 metres in length was walked during each of three pre-determined fortnightly periods (Table 1) and any glowing females which were observed along the route were recorded. It was felt that these three periods adequately incorporated the peak glowing season. Survey participants were required to commence each walk between 2200 and 2300 hours, and to terminate by 0000 hours.
Table 1: Two week periods for each of the three transect walks

Walk no.

Dates

1

9th – 22nd July

2

23rd July – 5th August

3

6th – 19th August

A slow strolling pace was recommended for the walks to reduce the risk of overlooking glowing females along the route. During the transect walks, survey participants were asked to record the habitat types which were utilised by the glowing females, to detail any artificial lighting at the site and also to mark the approximate position of any L. noctiluca individuals on the sketch map. If glowing females were not observed during the first two transect walks, survey participants were advised to abandon the final walk. This transect method was devised to standardise the results obtained and to facilitate site comparison.


3.0 Results
3.1 Recording coverage

Figure 1 displays the distribution of tetrads surveyed in 2001, which includes both the transect monitoring and the casual surveys. The survey attained quite widespread coverage of the county, although there was a slight bias towards the Chelmsford area, where the survey organisers were situated. There were fewer surveyors in the north and west of the county, and also in the extreme south near Grays. A total of 48 people took part, with many surveying more than one site. Overall, 57 locations were visited by survey participants (Appendix 1) and transect walks were completed at 35 of these sites.



Figure 1: Recording coverage in 2001 (map shows 47 tetrads within the survey)




3.2 Distribution of L. noctiluca in Essex

The survey illustrates that L. noctiluca is widespread but localised in Essex (Figure 2). This species occurs scattered throughout most of Essex, although there are very few records for the north and west of the county. L. noctiluca has been recorded at 43 sites since 1992 and was observed at 28 sites in 2001 (Appendices 2 and 3). There have been many colonies recorded on Danbury Ridge (five sites), around Creeksea (six sites) and at Langdon Hills (three sites) since 1992. Although these clusters of sites are quite close together, other colonies are much more isolated. For example, individuals were observed in the grounds of Saffron Walden’s hospital during the 2001 survey, which is many kilometres from the nearest extant colony.



Figure 2: Distribution of L. noctiluca records since 1992 (30 tetrads occupied)

Key: Black dots indicate 2001 records



White dots indicate records from 1992-2000
3.3 Declines

L. noctiluca has declined in areas such as Epping Forest which used to possess scattered colonies in the early 1900s (Leutscher 1974). Although the forest was particularly targeted during the 2001 survey, individuals were not observed at any of the five sites which were visited. Only one colony has been recorded within the forest since 1992, therefore L. noctiluca is probably very rare in this area. Searches in 2001 at other sites with old records for L. noctiluca were mostly unsuccessful. This species would appear to be extinct at Maldon Wick, Hazeleigh Wood, Chatham Green and the seawall at North Fambridge. Some colonies are also extremely threatened, predominantly by development pressures. For example, although several colonies were recorded in the grounds of the Braintree Freeport complex in 2001, an adjacent housing development has severely reduced grassland habitat availability, and consequently the number of individuals in one of these colonies has rapidly declined since the late 1990s.

3.4 Transect recording

L. noctiluca were observed at 16 of the sites where transect walks were conducted. A total of 507 glowing females were recorded during the transect walks. The majority of these individuals were observed in period one (9th - 22nd July), during which the highest count of the survey also occurred. In the subsequent walk periods, observations gradually declined and only 104 individuals were recorded in period three (6th - 19th August). The highest count during the final period occurred at Hadleigh Castle, which was the only site where more individuals were observed in the final walk period than in the previous two.
Overall, counts of L. noctiluca individuals were generally very low (Figure 3). Observations comprising only one glowing female occurred nine times during the survey. Although four counts comprising over 30 individuals did occur during the survey, three of these were recorded at One Tree Hill. The highest count of the survey was 76 glowing females, which were observed at One Tree Hill on July 11th.
F
igure 3: Frequency of counts

During three transect walks, 192 glowing females were observed at One Tree Hill, comprising 37% of the total number of individuals which were recorded in the survey (Table 2). Other sites where L. noctiluca was observed in relative abundance were Finches Nature Area and Manwood Chase. L. noctiluca occurred in very low abundance at Staneway, Dry Street and Hatfield Forest. Glowing females were observed in greatest concentration at One Tree Hill, where 19.20 individuals per 100 metres were recorded (Table 2). L. noctiluca individuals were also evident in high concentrations at Hadleigh Castle and Manwood Chase. Glowing females occurred in particularly low concentrations at Hatfield Forest (0.09 individuals per 100 metres) and Danbury Ridge. Individuals were very widely dispersed throughout a long transect route at the latter site (1,850 metres).
Table 2: Details of L. noctiluca monitoring at each site
Site

Total count


(%)

No. per 100m

One Tree Hill, Basildon*

192

37.8

19.20

Finches Nature Area, Canewdon*

54

10.6

11.25

Manwood Chase, Abberton

50

9.8

16.67

Hadleigh Castle, Hadleigh

42

8.3

19.09

Danbury Ridge Complex, Danbury*

40

7.9

2.16

Stow Maries Halt, Stow Maries*

30

5.9

8.57

Hospital Grounds, Saffron Walden

23

4.5

10.95

Herons Paddock, Little Baddow

16

3.2

3.20

Benfleet Downs, South Benfleet*

16

3.2

3.90

Shut Heath Wood, Little Braxted*

10

2.0

10.00

Iron Latch, Eight Ash Green*

9

1.8

3.60

Bulford Mill Lane, Cressing

7

1.4

2.33

Grays Chalk Quarry, Grays*

6

1.2

6.00

Staneway, Basildon*

5

1.0

5.00

Dry Street, Basildon

5

1.0

5.00

Hatfield Forest, Takeley*

2

0.4

0.09

507







* indicates site is a nature reserve
3.5 Nature reserves

Transect recording was relatively evenly divided between nature reserves and non-nature reserve areas. The total length of the nature reserve transect routes was 12,240 metres, compared with 15,880 metres for those at non-nature reserve sites. During the survey, 364 glowing females were recorded at nature reserves, comprising approximately 72% of the total number of individuals which were observed. The highest count which occurred at a non-nature reserve area was 27, compared with the 76 individuals that were observed at One Tree Hill, which is a nature reserve site. Nature reserves were therefore important areas for L. noctiluca in the survey.


3.6 Habitats

The majority of the glowing females which were observed during the survey were utilising grassy meadows and scrub (Figure 4). These meadows were generally botanically diverse and predominantly unimproved. L. noctiluca individuals were also recorded on garden lawns, underneath hedgerows and in woodland areas. In the latter areas, glowing females were observed more frequently in woodland rides than underneath dense tree canopy. Tall overgrown hedgerows, possibly of some antiquity were utilised by glowing females in preference to lower, more managed examples. Individuals were recorded in less abundance on other linear habitats such as roadside verges and disused railway lines. Very few glowing females were observed within the proximity of aquatic habitats or in damp grassland areas. Although some of the sites in the survey comprised arable areas and improved grassland, there were no glowing females detected in these habitat types.


F
igure 4: Percentage of L. noctiluca females in different habitats
3.7 Lighting

Table 3 illustrates the number of females which were recorded under different lighting conditions. Approximately 78% of females were observed at unlit sites, therefore L. noctiluca was most abundant in totally dark conditions. Lower abundance was evident at sites with house and vehicle lights. Only six females were seen displaying at sites with streetlights.



Table 3: L. noctiluca females observed under different lighting conditions

Lighting


No. females

%
No lights

398

78.5

House lights only

61

12.0
House and vehicle lights

30

5.9

Vehicle lights only

12

2.4

Street lights only

6

1.2

507





3.8 Management of sites

At the majority of the sites where L. noctiluca individuals were observed during the survey, the grassland is managed by regular mowing. All of the meadows where glowing females were present are mown at least once a year. However, individuals were also recorded in a variety of less frequently managed tall grassland habitats such as woodland rides, where mowing or scrub clearance is only occasionally conducted. At the only site which is grazed by livestock that was visited during the survey (Hatfield Forest), L. noctiluca individuals occurred in very low abundance. Individuals were observed in greater abundance at sites where rabbit grazing was evident, particularly on the heathy grassland of Little Baddow Heath (part of the Danbury Ridge transect).


4.0 Discussion

The widespread but localised distribution of L. noctiluca in Essex (Figure 2) is similar to the national distribution of this species. In Essex, it would appear that L. noctiluca only occurs where there are suitable habitats such as unimproved meadow or ancient woodland, which are rare habitats in the county (Corke 1984). The dearth of favourable areas in Essex explains the localised distribution of this species. Disturbed habitats such as improved pasture may be unfavourable because of low snail populations, which are the food source of L. noctiluca larvae. In areas where there are extensive patches of suitable habitat such as the large ancient woodlands and meadows of Danbury Ridge, there are many colonies evident in close proximity.


The fragmentation of suitable habitats and thus isolation of colonies is compounded by the sedentary nature of this species. The adult females cannot fly to disperse and colonise new areas, whilst the larvae are not thought to move far in search of food (Tyler 2002). The larvae are reported to move approximately five metres an hour, but they may find roads or arable fields a significant barrier to dispersal. Isolated colonies such as the one in the grounds of Saffron Walden’s hospital may therefore lose genetic diversity and ultimately sustain insufficient individuals to remain viable.
Corke (1984) states that L. noctiluca appears to be rare in Essex, which was seemingly confirmed by the county recorder having records of only 13 sites. However, with the 2001 survey collating records from 43 sites since 1992, L. noctiluca is not as rare as was first thought but is significantly under-recorded. In comparison with other counties, Essex has a relatively high number of L. noctiluca colonies. For example, 58 colonies were recorded in a ten year survey of Gloucestershire from 1980 to 1990, which is believed to be one of the most favourable counties for this species in Britain due to the presence of extensive tracts of unimproved limestone grasslands (Alexander 1992).
Despite the relatively high number of Essex colonies, 37% of all of the glowing females which were observed in the transect survey were recorded within one site (One Tree Hill). Counts were generally low outside of this site (Figure 3), so caution must be exercised in declaring L. noctiluca as ‘safe’ in a county context. The important colony at One Tree Hill is afforded some protection because the area is within a nature reserve and is therefore regularly monitored. Consequently, the main threat to this colony is probably from the trampling of non-glowing females by interested naturalists and members of the public partaking in glow-worm walks.
Statistical evidence of declines in L. noctiluca abundance is scarce, but many naturalists believe that there has been a steady decline in the British population since the 1950s (Tyler 1994). Throughout the UK, this species has disappeared from many of the sites at which it was once common and this is reflected in the information collected during this study. Cole (1899) states that there were many colonies in Epping Forest in the late 1800s and even in the early 1900s, L. noctiluca was noted as having a patchy distribution within this area (Leutscher 1974). However, there has only been one observation of L. noctiluca in Epping Forest since 1992 despite extensive searches within this area during the 2001 survey, therefore leading the authors to believe that L. noctiluca is currently rare within the forest.
The decline in L. noctiluca abundance within Epping Forest may be attributed both to the reversion of many of the favourable open grassy areas to woodland and to the close proximity of the forest to London. Succession has occurred because grazing and traditional woodland management practices have decreased since the early 1900s. Additionally, air pollution from London may have detrimentally affected colonies within this area because snails can accumulate chemicals deposited onto vegetation and L. noctiluca individuals could subsequently become exposed to these pollutants (Tyler 1994).
The majority of L. noctiluca colonies that were observed during the 2001 survey were found on nature reserves and in other areas with no artificial lighting (Tables 2 and 3). The intensification of agriculture since the 1950s, coupled with the inappropriate management of rural roadside verges may have resulted in the loss of many colonies in the wider countryside. Development is now the predominant threat to colonies which occur outside of nature reserves. This problem is compounded by the lack of any legal protection for this species. Colonies within the vicinity of Grays and the Braintree Freeport complex are particularly threatened and several favourable sites have been destroyed in these areas during the last few years. Scrub encroachment is probably the main threat to colonies which occur on nature reserves. Although scrub is an important habitat for L. noctiluca in Essex, encroachment must be carefully controlled because colonies are infrequently found within mature woodland.
Streetlights were only present at one site where L. noctiluca were observed, probably because artificial lighting is known to distract flying males when they are searching for glowing females (Tyler 2002). Any attempt to erect new streetlights near to a known colony must therefore be opposed where pedestrian safety is not a major issue.
4.1 Conservation

L. noctiluca appears to be under no immediate threat from extinction in Essex, although many of the colonies which exist are isolated and most are relatively small. Protection of the remaining populations which occur outside of nature reserves is a priority and where development is planned for a site that currently supports a colony, the planning proposals should be opposed. It is intended that this survey will continue in future years in an effort to detect more new colonies, which are undoubtedly present due to the significant under-recording of this species. There are still many old records to be investigated in areas such as Thorndon Park.


4.2 Transect monitoring

The transect monitoring that occurred during the survey provided valuable data on the abundance of L. noctiluca at different sites. It is important that these transect walks are undertaken in future years using exactly the same methodology so that the progress of L. noctiluca in Essex can be ascertained. This monitoring will detect the long-term trends in the abundance of L. noctiluca and will determine whether future research or conservation measures need to be implemented. These walks will enable the effectiveness of the current conservation management strategies to be ascertained and altered if necessary.


4.3 Site management

Little is known about how to manage sites to encourage L. noctiluca (Tyler 2002). Mowing is an important management activity at most of the sites within which glowing females were observed, so this should be continued to prevent scrub encroachment. Alexander (1992) states that the main objective of management for L. noctiluca should be to maintain vegetation structure and snail populations. Where possible, the available L. noctiluca habitat should be extended in an effort to link it to other favourable areas. The use of chemicals, especially Mollusicides, should be avoided as they have detrimental impacts upon snail fauna. Patches of scrub and dead wood should be retained within open grassland areas to provide cover for larvae and snails (Alexander 1992). It is essential that the collection of glowing females is discouraged because many of the colonies in Essex are very small and particularly vulnerable to extinction.


5.0 Conclusion

The short-term future of L. noctiluca in Essex appears to be relatively secure because this species is not as rare as was previously thought. However, with the exception of the population that was recorded at One Tree Hill, most of the colonies which were observed during the survey were small and many were isolated. Development, pollution and the neglect of sites are the major threats to L. noctiluca in Essex and monitoring of known colonies should continue in future years to ascertain long-term trends and allow conservation measures to be implemented if necessary.




Acknowledgements

I would like to thank all of the survey participants and everyone who submitted records. The following individuals deserve special thanks: Claire Cadman, Geoff Ford, Mandy Greig, Peter Harvey, Martin Heywood, Chris Johnson, Andy McGeeney, Robin Scagell, Nick Stanley, John Tyler, Graham Watkins and Lin Wenlock. My gratitude is also extended to English Nature and Essex Wildlife Trust for supporting the survey, and to Writtle College for providing finance and resources for the duration of the project. The distribution maps (Figures 1 and 2) were produced using Dr. Alan Morton’s DMAP programme.


References
Alexander, K N A 1992 The glow worm, Lampyris noctiluca (L.), in Gloucestershire and its conservation. The Gloucestershire Naturalist. 5: 1-5
Cole, W 1899 Glow-worm and frog. The Essex Naturalist. 11: 144-145
Corke, D 1984 The nature of Essex. Barracuda Books, Buckingham
Leutscher, A 1974 Epping Forest – its history and wildlife. David & Charles, London
Tyler, J 1986 The ecology and conservation of the glow-worm, Lampyris noctiluca (L.) in Britain. Atala. 10-12: 17-19
Tyler, J 1994 Glow-worms. Tyler-Scagell, Sevenoaks
Tyler, J 2002 The glow-worm. Lakeside Press, Sevenoaks

Appendix 1: Grid references for sites surveyed in 2001





TL379016

Cornmill Meadows, Lee Valley

TL448010

Epping Thicks, Epping Forest

TL545207

Hatfield Forest, on plains

TL548212

On verge near bridge, Takeley

TL552386

Saffron Walden Hospital, near Ambulance Station

TL617216

Dunmow Railway Cutting

TL628134

Hayron’s Lane, High Easter

TL630030

Gorrell’s Farm, Highwood

TL637064

Colley Bridge Lane, Cooksmill Green

TL639012

Mill Green Common

TL639067

Green lane, Roxwell

TL655069

Newney Green

TL677070

Cow Watering Lane, Writtle

TL682047

Hylands Park, Writtle

TL694047

In garden by railway, Widford

TL714152

Chatham Green

TL728283

Nichols Farm, Shalford

TL739062

Sandford Mill, Chelmsford

TL769221

Behind platform at Braintree Freeport Railway Station

TL771219

On landscaped area, Braintree Freeport

TL775202

Bulford Mill Lane, Cressing

TL7806

Danbury Ridge Complex

TL786059

Garden backing onto Spring Wood, Danbury

TL787075

Herons Paddock, Little Baddow

TL788049

Hitchcock’s Meadows, Danbury

TL793063

Twitty Fee, Danbury

TL809068

St. Michael’s Churchyard, Woodham Walter

TL834043

Hazeleigh Wood

TL846030

Maldon Wick

TL853133

Shut Heath Wood, Little Braxted

TL856435

The Valley Walk, Rodbridge

TL872092

Scraley Road, Little Totham

TL952260

Iron Latch Nature Reserve, Eight Ash Green

TL954256

Iron Latch, by railway bridge, Eight Ash Green







TM008199

Manwood Chase, Abberton

TM204190

Great Holland Pits


TM212268

Bramble Island, Great Oakley

TM217243

Skippers Island







TQ407967

Fairmead and Almshouse Plain, Epping Forest

TQ431982

Gregson’s Ride, Epping Forest

TQ436955

Roding Valley Nature Reserve, Loughton

TQ607792

Grays Chalk Quarry

TQ683874

Marks Hill, Willow Park

TQ684942

Mill Meadows, Billericay

TQ685882

Staneway, Basildon

TQ695867

Dry Street, Basildon

TQ705865

One Tree Hill, Basildon

TQ736972

Hanningfield Reservoir

TQ781858

Benfleet Downs

TQ800860

Hadleigh Castle Country Park

TQ810860

Hadleigh Castle

TQ835991

Stow Maries Halt

TQ853965

Seawall, North Fambridge

TQ905945

Finches Nature Area, Canewdon

TQ931959

Sailing club car park, Creeksea

TQ932962

Verge of lane, Creeksea

TQ933965

By railway bridge, Creeksea


Appendix 2: Sites at which L. noctiluca were observed in 2001

TL694047
In garden by railway, Widford

TL545207

Hatfield Forest, on plains

TL548212

On verge near bridge, Takeley

TL552386

Saffron Walden Hospital, near Ambulance Station

TL769221

Behind platform at Braintree Freeport Railway Station

TL771219

On landscaped area, Braintree Freeport

TL775202

Bulford Mill Lane, Cressing

TL7806

Danbury Ridge Complex

TL786059

Garden backing onto Spring Wood, Danbury

TL787075

Herons Paddock, Little Baddow

TL788049

Hitchcock’s Meadows, Danbury

TL793063

Twitty Fee, Danbury

TL853133

Shut Heath Wood, Little Braxted

TL952260

Iron Latch Nature Reserve, Eight Ash Green

TL954256

Iron Latch, by railway bridge, Eight Ash Green







TM008199

Manwood Chase, Abberton







TQ607792

Grays Chalk Quarry

TQ685882

Staneway, Basildon

TQ695867

Dry Street, Basildon

TQ705865

One Tree Hill, Basildon

TQ781858

Benfleet Downs

TQ800860

Hadleigh Castle Country Park

TQ810860

Hadleigh Castle

TQ835991

Stow Maries Halt

TQ905945

Finches Nature Area, Canewdon

TQ931959

Sailing club car park, Creeksea

TQ932962

Verge of lane, Creeksea

TQ933965

By railway bridge, Creeksea


Appendix 3: Sites at which L. noctiluca were recorded from 1992 to 2000


TL522366

Disused railway line, Wendens Ambo

TL532187

Hatfield Forest

TL790314

Broakes Wood

TL805175

White Notley railway line (used)

TL837131

Chantry Wood, Wickham Bishops

TL976210

Roman River Valley







TQ431982

Goldings Hill, Loughton

TQ5878

Mill Wood Pit, Grays

TQ598782

Grays

TQ599793

Grays

TQ7386

Wat Tyler Country Park

TQ778891

Wheelers, Rayleigh

TQ918974

Railway line (used), Creeksea

TQ9296

The Cliff, Burnham

TQ934957

Seawall, Creeksea







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