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Suffolk Natural History, Vol. 32
INVASION OF DRAGONFLIES IN 1995 H. MENDEL & M. C. MARSH The long, hot and dry summer of 1995 (breaking several records; the hottest August ever!) will be remembered in future decades as an exceptional time for insect migration. The massive influx of dragonflies included two species not previously recorded in Britain - Crocothemis erythraea (BrĂźlle) Scarlet Dragonfly (previously recorded from the Channel Isles) on the Lizard Peninsula in Cornwall, 7th August 1995 (Jones, 1996) and Sympetrum pedemontanum (Allioni) Banded Darter at a site on the southern edge of the Brecon Beacons in Powys, 16th-17th August 1995 (Silsby, 1995a, b). It is tempting to speculate that these individuals may have flown over East Anglia on migration westwards. However, many of the migrants recorded in western Britain quite likely had a different origin to those that entered Britain via the eastern counties. In Suffolk it was the invasion of Sympetrum flaveolum (L.) Yellowwinged Darter with lesser numbers of Sympetrum danae (Sulzer) Black Darter that will be remembered. It is likely that Sympetrum vulgatum (L.) Vagrant Darter also occurred in Suffolk but none of the records was confirmed. A report of Hemianax ephippiger (Burmeister) Vagrant Emperor dragonfly from Newbourn is presumed to be a case of mistaken identity and cannot be accepted. The immigration seems to have started on the 3Ist July and coincided with a large area of high pressure which became established over Scandinavia from 29th July, resulting in warm easterly winds which persisted for much of August, occasionally switching to the south-east or north-east (Tunmore, 1996). Interestingly, 'On July 31st hundreds [of S. flaveolum] were seen leaving the shores of Holland' (Silsby, 1995a). The immigration also included more familiar species - Aeshna mixta (Latreille) Migrant Hawker, Sympetrum sanguineum (MĂźller) Ruddy Darter and Sympetrum striolatum (Charpentier) Common Darter - that are normally resident in Britain. It is a pity, although understandable, that the excitement created by the appearance of so many rarities distracted attention away from these more familiar migrant species. Although S. danae and 5. flaveolum can usually be identified with confidence, S. vulgatum proved very difficult to recognise, even in the hand. In particular, it was not realised by many dragonfly enthusiasts that the black 'moustache' marking on the face (at the base of the frons and continuing down the sides of the eyes) which distinguishes S. vulgatum from S. striolatum is also found in S. sanguineum. Heath and Milford (in press) have critically examined the various characters that are used to separate the three species, using specimens recorded in Norfolk in 1995. None of the putative Suffolk S. vulgatum was critically examined in the hand and all of the records must be regarded as provisional and unconfirmed. The list of records below, arranged alphabetically by locality, includes only those species not normally found in Suffolk (Mendel, 1992), viz.
Trans. Suffolk Nat. Soc. 32 (1996)