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FIVE-SPOT B U R N E T MOTH ZYGAENA IN SUFFOLK
TRIFOL1I
(ESPER)
H. MENDEL & R. N. MACKLIN Burnets are a group of attractive, brightly-coloured, day-flying moths that will be familiar to most naturalists. They appear easy to identify, and many populär guides reinforce that impression, but some species are extremely challenging even for the more experienced lepidopterist. In particular, the identification of the Five-spot Burnet Zygaena irifolii (Esper) and the Narrow-bordered Fivespot Burnet Z. lonicerae (Scheven) is fraught with difficulty. Separation relies on comparative characters; the relative length of the forewing, the precise shape of the upper angle of the hindwing and the breadth of the black border of the hindwing. Individuais with confluent spots on the forewing are found regularly in the Five-spot Burnet and are a characteristic feature of populations. Similarly aberrant individuals are much rarer in the Narrow-bordered Five-spot Burnet. The Narrow-bordered Five-spot Burnet (race latomarginata Tutt) is fairly common in Suffolk, so familiar that its mouthful of a name is usually shortened to 'Five-spot Burnet'; it is assumed that Z. trifolii is no longer found in Suffolk. To avoid this confusion we will use the scientific names from this point onwards. According to Skinner (1984), although locally common in south-west England and in Wales, Z. trifolii (race decreta Verity) is 'now extremely rare, if not extinct' in south-east England and East Anglia. However, by the following year the presence of a colony in north-east Norfolk had been confirmed (Skinner, pers. comm.) and is marked on the distribution map in Tremewan (1985). The two species have different habitat requirements. Z. lonicerae, the commoner species, is most numerous on heathland in Suffolk but is also associated with a variety of rough ground habitats, meadowland and, occasionally, wetland sites. Larvae feed on a ränge of trefoils, clovers and vetches. Z. trifolii is a species of wet heathland, damp meadows and marshes where the larval foodplant Lotus pedunculatus Cav. (greater bird's-foot trefoil) grows. On 9th July 1992, during the Suffolk Dragonfly Survey, HM identified several Z. trifolii inhabiting an area of freshwater marsh on Walberswick N.N.R. (TM4573). One specimen with an attractive pattern of confluent spots on the forewing (ab. glycirrhizae Hübner) was photographed (see cover). In 1996 a population of Z. trifolii was discovered by RNM in a small area of fen at North Warren (TM4458). Nature reserve staff had previously assumed that the moths were Z. lonicerae. Thirty moths were counted on July 22nd, nectaring on Vicia cracca L. (tufted vetch) and Cirsium palustre (L.) Scop. (marsh thistle). Management of the area (bi-annual cutting) over the past six years, aimed primarily at maintaining botanical diversity, has resulted in a healthy population of greater bird's-foot trefoil. It is interesting that the relative status of Z. trifolii and Z. lonicerae in East Anglia and south East England has reversed over this Century (Tremewan, 1980). In Suffolk, Morley (1937) describes Z. lonicerae as 'Distinctly rare; unnoticed since 1890' whereas Z. trifolii was 'Still abundant in restricted areas'. The latter species has become very scarce in Suffolk and the only post1950 voucher specimens at Ipswich Borough Council Museum are labelled
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'Barton Mills. C. W. Pierce. 24/7/67' and 'Walberswick, Suffolk 23.7.69. H. E. Chipperfield'. Z. trifolii is easily overlooked and other populations are sure to be found associated with freshwater marshes along the coast, in the Waveney Valley or on Breckland fens. Acknowledgements Our thanks to Mr Bernard Skinner and Mr W. G. Tremewen for confirming the identity of the Suffolk Z. trifolii from a colour transparency (Walberswick) and a voucher specimen (North Warren). Thanks also to English Nature through Cliff Waller (Warden) for access to Walberswick National Nature Reserve. References Morley, C. (ed.) (1937). The Lepidoptera of Suffolk. Suffolk Naturalists' Society. Skinner, B. (1984). Colour identification guide to moths of the British Isles. Harmondsworth: Viking (Penguin). Tremewan, W. G. (1980). On the status of Zygaena (Zygaena) trifolii decreta Verity (Lepidoptera: Zygaenidae) in south-east England. Entomologist's Gaz., 31: 143-145. Tremewan, W. G. (1985). Zygaenidae. In: Heath, J. & Emmet, A. M„ 1985. The moths and butterflies of Great Britain and Ireland. Vol. 2, Cossidae Heliodinidae, pp. 74-123. Great Horkesley: Harley Books. Howard Mendel The Museum, High Street, Ipswich IP1 3QH Rob Macklin Site Manager, RSPB North Warren & Aldringham Walks, Racewalk, Priory Road, Snape, Saxmundham IP17 1SD
Trans. Suffolk Nat. Soc. 33 (1997)