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THE SPECKLED WOOD PARARGE AEGERIA L. IN SUFFOLK 2000–2002 R. G. STEWART The Speckled Wood Pararge aegeria L. was recorded in 459 out of Suffolk’s total of 1088 tetrads during the 1995–1999 Millennium Survey of Suffolk Butterflies (Stewart, 2001) This was a large increase compared to the records from just 50 tetrads during the previous county-wide survey, which ended in 1985. (Mendel & Piotrowski, 1986). However, there had been significant new records during the years between the two surveys, one example being the confirmation of this species on the Suffolk coast (Beaumont, 1991). The information in ‘The Millennium Atlas of Butterflies in Britain and Ireland’ (Asher et al., 20001) was not available until after the text of the Suffolk book (Stewart, 2001) was completed. The national results for the Speckled Wood revealed a 54% increase in 10 km square distribution, compared to records from 1970–1982, the numbers being 1462 and 948 respectively. The text highlighted the species being ‘widespread in Norfolk and Suffolk by the end of the twentieth century’ with the authors identifying False Brome Brachypodium sylvaticum, Cock’s-foot Dactylis glomerata, Yorkshire Fog Holcus lanatus and Common Couch Elytrigia repens as the main larval food plants. The importance of both sexes feeding on aphid honey dew was also stressed. They also noted a wider range of habitats in the south of England, including lanes and tracks between tall hedgerows, scrub areas, parks and gardens, and recommended leaving patches of tall, shady grassland in urban areas. They also stressed the importance of encouraging the Speckled Wood in more intensively farmed areas by maintaining or planting ‘a network of small woods and hedgerows, with their associated native grasses’. Other factors mentioned in connection with its increase in range were the utilisation, with the White admiral, of shady woodlands arising from lack of coppicing and the Speckled Wood’s abundance has been found to increase following cool wet years. The authors also comment that ‘a recent model of the effects of climate and habitat availability on the expansion of the species has predicted that, if current climate changes continue, most of Britain will become climatically suitable for the butterfly during the twenty-first century’. The word ‘most’ is significant because the authors then stress that lack of suitable habitat explains the butterfly’s sparseness in north Cambridgeshire and south Lincolnshire, areas they describe as ‘arable prairies’ with ‘a scarcity of suitable woodland’. I have quoted these findings at some length because they may help to explain the continued increase of the Speckled Wood in Suffolk since the end of the Millennium Survey. In 2000 there were 47 new tetrad records and the county-wide survey of churchyard butterflies (Stewart, 2002), contributed to an additional 77 in 2001 and in 2002 there was a further 31. This total of 155 new tetrad records over three years was much higher than for any other Suffolk Species. In 2000 and 2001 the Speckled Wood, in terms of tetrad coverage in Suffolk, was the fifth highest. In 2002 it was, at 171, above the 167 of the Meadow Brown and only eclipsed by the Large White on 186.
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Speckled Wood
0
9
8
7
6
5
4
1995-1999 1980-1985 2000-2002 3
6
7
8
9
0
1
2
3
4
5
Bearing in mind the comments of Asher et al. (2001) about the habitat needs of the Speckled Wood it is worth analysing where these new records have come from. There has been little or no change in several partial 10 km recording squares in the north-east of the Suffolk recording map: TG50 near Yarmouth still has no records, there is now a single record in TG40 west of Great Yarmouth, TM49 to the west of Lowestoft has risen from three to four and TM28 to the south-west of Bungay still has just a single tetrad record. Theses are probably the recording areas most devoid of suitable habitat for the Speckled Wood and the scarcity of this species is echoed in the results from the ‘Millennium Atlas of Norfolk Butterflies' (Watts & McIlwrath, 2002) which also traditionally low in resident or visiting recorders, not just for butterflies, so under-recording could be a significant factor. This factor is probably even more relevant in the TL tetrads that are mainly in West Suffolk. During the Millennium Survey the Speckled Wood was recorded in 53·3% of the TL tetrads but in only 35·1% of the TM tetrads. Three years later the respective figures are 59·9% and 54·2% in 2002 records of all butterfly species in Suffolk covered just 74 TL tetrads (17·4%) compared to 235 TM tetrads (35·3%, i.e. more than double). Of the 155 new tetrad records for the Speckled Wood between 2000 and 2002 just 28 came from the TL tetrads. This part of Suffolk has any of the habitat requirements
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needed by the Speckled Wood and from the evidence of the last three years its limited spread in West Suffolk arises from under-recording. To balance the recording problems noted above, there has been an considerable increase in records of the Speckled Wood in many areas. TM13 on the Stour estuary had no records in its 20 tetrads before 2000 – now it has eleven. Adjoining TM03 has increased from five to eleven in the last three years and TM14, covering most of Ipswich, has increased from ten to twenty. Again an adjoining square, TM24, centred on Martlesham, has also registered a considerable three year increase, rising from seven seventeen. The only comparison in the TL tetrads is in TL74, around Clare, with an increase from five to eleven of the available eighteen tetrads. The fact that four of the five 10 km recording squares, where significant increases have occurred, are connected suggest genuine colonisation but little research has been carried out for this species: ‘There is little information on the mobility of this butterfly, but the recent range expansion demonstrates considerable ability to colonise new habitat’. (Asher et al., 2001). My own detailed experience is limited to the butterfly transect along the Fynn Valley between Tuddenham and Playford. This cover four tetrads in which the Speckled Wood had not been recorded during the Millennium Survey. In 2000 it was recorded in all four, seen on nine of the fifteen transect sections and had an annual index of 59. Foot and Mouth restrictions prevented study in 2001 but in 2002 it was recorded on eleven transect sections and the annual index rose to 85. Detailed local butterfly records of any area previously without the species and recently colonised would be interesting to analyse, and could add vital information about its ability to colonise new habitats. (See Plate 2) References Asher, J., Warren, M., Fox, R., Harding, P., Jeffcoate, G., Jeffcoate, S., (2001). The Millennium atlas of butterflies in Britain and Ireland. Oxford University Press, Oxford. Beaumont, A. (1991). Speckled Wood in Dunwich Forest. White Admiral 18:7. Mendel, H. & Piotrowski, S. H. (1986). The butterflies of Suffolk. Suffolk Naturalists’ Society, Ipswich. Stewart, R. (2001). The Millennium atlas of Suffolk butterflies. Suffolk Naturalists’ Society, Ipswich. Stewart, R. (2002). The Suffolk ‘butterflies in churchyards’ survey 2001. Trans. Suffolk Nat. Soc., 38: 87–101. Watts, B. R. & McIlwrath, B. J. (2002). Millennium atlas of Norfolk butterflies. Butterfly Conservation Norfolk Branch, Norwich. Richard Stewart ‘Valezina’ 112 Westerfield Road Ipswich Suffolk. IP4 2XW
Trans. Suffolk Nat. Soc. 39 (2003)
R. G. Stewart Plate 2: Speckled Wood, Pararge aegeria L. in Christchurch Park, Ipswich 2002 (p. 25).