The Smaller Moths of Shropshire: their Status, Distribution and Ecology
By Godfrey Blunt
The Long Mynd and the Strettons may have some of the best historical data for larger moths in Shropshire, but until recent years remarkably little work had been done on the micro-moths here, and it remained the county’s most under-recorded major locality for this group of our Lepidoptera. Fortunately the light-trapping programmes initiated by Graham Wenman and Mike Shurmer at Church Stretton and All Stretton, and fieldwork by several recorders on the Long Mynd, have gone a long way to remedying the situation.
So what have we found out about the smaller moths of our area? Well, quite a lot, though a lot also remains to be discovered. The first point to note is the richness of the area’s micro-moth fauna. A surprisingly large number of species have been noted here. They include many that are found in Shropshire mainly in the warm, dry lowlands of the Severn valley and northern plain, and for these the Stretton valley seems to act as an extension of lowland Shropshire into the hills. This extension via the Church Stretton fault is clearly visible in the view looking north-eastwards from the road between The Burway and Boiling Well.
This lowland aspect in the fauna arises from a locally mild climate, at least partly the product of a rain-shadow cast by the Long Mynd on the Strettons. A good indicator of this is the leaf-miner Gracillaria syringella, which has large populations on ash in the cool, wet upland regions of the county but in the warmer and drier lowlands feeds more on lilac and occasionally privet. It is found on all three foodplants in Church Stretton, its populations here being particularly large on lilac, suggesting that the local climate has as much or more in common with the Shropshire lowlands as the uplands. A similar rain-shadow effect may be observed in the northern foothills of the Mynd at Smethcott and Picklescott, where the warm, sheltered roadsides harbour a few moths at their highest altitudes in Shropshire, such as the Rose Leaf-miner Stigmella anomalella.
Many species that colonise Shropshire do so across the warm, dry lowlands before spreading into hill country. A good example is the Firethorn Leaf-miner Phyllonorycter leucographella that arrived in the Severn valley in 2004 and had spread into the Shropshire hills at Church Stretton by 2011. The Cypress Tip Moth Argyresthia cupressella turned up first at Shifnal in 2013, rapidly followed by one at Church Stretton only ten days later. But two new arrivals in Shropshire were discovered first in our area, namely Psychoides filicivora at Little Stretton in 2010, and Cydia illutana that Graham trapped at Church Stretton this year. The potential for monitoring the arrival or spread of other micro-moths into hill country in the Stretton area is great.
And what of the Long Mynd itself? Our observations here have turned up some fascinating things. In the first place, we have found on the Mynd none of the more strictly north-western British micro-moths which reach their range limits in Shropshire. These are largely confined to the Stiperstones. Whether this finding adds anything to the debate about the relevant natures of these two ridges as “upland heath” in the strict botanical sense is unclear, but it is intriguing; it may support those who consider the Stiperstones to be “upland heath” but not the Long Mynd. The healthland moths found on the Mynd are those with wider national ranges, and they include Shropshire’s largest recorded populations of Acleris hyemana, Argyrotaenia ljungiana and Exapate congelatella and our only record to date of Aroga velocella. In 2005 Wildmoor Pool became the site of the rediscovery of Stigmella myrtillella, a leaf-miner on bilberry not found in Shropshire since 1889.
Further observations on the Mynd have helped us assess the effects of sheep-grazing on micro-moth populations. We have found a distinct contrast in population sizes of Rhopobota naevana, a bilberry-feeder, between areas which are heavily grazed and those that are lightly grazed, with a hundred-fold reduction or more where sheep regularly nibble bilberry plants; it appears that in doing so they destroy the eggs or larvae of the moth, which live on the shoot tips. The grass-veneer Agriphila straminella, though numerous on Shropshire’s high-altitude heaths, clearly lives at highest density among grasses which are least palatable to sheep, notably mat-grass Nardus stricta and purple moor-grass Molinia caerulea.
On the summit plateau Pole Cottage, with its isolated shelterbelt of beech trees, affords good opportunities to study micro-moth adaptations to some of the more extreme climates that Shropshire can offer. The longhorn moth Adela reaumurella, whose dancing swarms of males are such a feature of lower altitudes on the Mynd, has a small population at Pole Cottage; so too does the nettle-tap Anthophila fabriciana and the leaf-miner on hawthorn Parornix anglicella. We cannot say as yet whether these are permanent colonies able to endure winters at this altitude, or whether they are temporarily established by adults coming from lower elevations; this is a study we have lined up for the future. Two leaf-miners on beech, Phyllonorycter maestingella and Stigmella tityrella, do appear to be permanently established at Pole Cottage, where their populations are distinctly larger on the lee side of the shelterbelt than on the exposed side. The Brown China-mark Elophila nymphaeata lives in the isolated pool next to Pole Cottage, where the aquatic habits of its larvae enable it to cope with the severe climate at that altitude.
This is just a brief summary of the micro-moths of the Long Mynd and the Strettons, the nature of the fauna found here and the factors that influence their distributions and populations. I hope it whets the reader’s appetite. There are now good resources, both books and websites, to help newcomers tackle the smaller moths, and this group is not the province of a handful of specialists that it may once have been. The Strettons and Long Mynd are an excellent area in which to carry out such studies, with much achieved here in the last few years and many possibilities for further investigations of these fascinating and beautiful creatures.