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NEWSLETTER No. 15 -  Summer 1986

WEST MIDLANDS BRANCH, BUTTERFLY CONSERVATION

 

Progress Report : White-letter Hairstreak

A report on the second year of this W.W.F. funded project has recently been produced by Martyn Davies who continues to co-ordinate the work on behalf of the West Midlands Branch. Not surprisingly, fieldwork last year was adversely affected by the weather, but nevertheless further progress was made. At Haugh Wood outside Hereford, where a mark and recapture experiment is taking place, the population was only about 40% of the 1984 level, with 200 adults marked, as opposed to 486 the previous year. This pattern was probably replicated throughout the insects' range and many recorders reported very low numbers or in some cases a complete absence at known sites. Martyn is at pains to point out in the report, however, that absence should not be equated with extinction. The butterfly does seem to be able to exist at fairly low densities and its traditional elusiveness means that it is very easy to overlook. A picture is emerging of a butterfly that was seriously under-recorded in the past and, for many counties, this still remains the case. In our own region the recording situation is very patchy and for many areas, the report appears to be documenting a shortage of recorders rather than a shortage of butterflies. Martyn emphasises once again the relative ease with which the non-adult stages may be found by searching Elm trees, and the need for butterfly enthusiasts everywhere to make a real commitment to search for eggs during the Winter and larvae/pupae in May and June. A set of over forty slides has now been prepared showing all stages of the life cycle and a guide to Elm identification, in the hope that this will encourage more work in under-recorded areas. If any individual, county trust or other group would like to borrow these slides, please contact Martyn.

Martyn's efforts, together with that of the three regional co-ordinators, to contact county recorders and nature conservation trusts is beginning to pay dividends and a national network is slowly being established which hopefully will enable, by the end of the project, a reasonable assessment of the butterfly's current distribution. Particular efforts were made in 1985 to improve our current knowledge about the insect's status in Wales, and further records from the principality are especially welcomed.

An interesting section of the report concerns White Letter Hairstreak aberrations. Reference was made in our last Newsletter to var. albovirgata found at Haugh Wood. A subsequent visit to the Natural History Museum by Barry Fleming and Martyn revealed that there were only four previous specimens of this particular aberration, the first dating back to 1857 from the Forest of Bondy in France and the most recent being from Tilshead, Wiltshire back in 1956. There are very few named aberrations of this butterfly, which perhaps partly explains the lack of historical records from the 'age of collecting' around the turn of the century.

Overall, despite lower population levels last year, there seems no reason to revise the note of cautious optimism expressed at the end of the first year's report. New records have continued to come to light and there is clear evidence that the butterfly is able to survive, perhaps in smaller numbers on non-flowering Elm trees, including quite small suckers. It is also clear that, although Wych Elm might be preferred, and the larger colonies may be associated with this species, English Elm and Smooth-leaved Elm are both frequently used. While there have undoubtedly been losses resulting from Dutch Elm disease, it can be confidently predicted that a more encouraging picture would emerge of the butterfly's current distribution if only more could be persuaded to search for it.

Martyn is generous in his acknowledgements of the assistance given by other people, but we owe most to Martyn himself for the hard work and expertise he has brought to the project. Although it is invidious to single out the efforts of one other individual among the many who have contributed to the study, it seems right to acknowledge the efforts of branch member Barry Fleming, who has been the mainstay of the mark and recapture work at Haugh Wood. It is probably true to say that, after marking nearly 700 White Letter Hairstreaks in two years, Barry has probably handled more of these attractive little butterflies than the rest of us have seen in our life.